Studies were carried out for two years to evaluate the effect of methods of sowing and weed control practices on the productivity of transplanted and direct wet-seeded rice in Dera Ismail Khan, NWFP, Pakistan. The exp...Studies were carried out for two years to evaluate the effect of methods of sowing and weed control practices on the productivity of transplanted and direct wet-seeded rice in Dera Ismail Khan, NWFP, Pakistan. The experiment was laid out in a randomized complete block design with a split plot arrangement. The planting techniques viz. transplanting and direct seeding were maintained in main plots while weed control practices included the use of granular herbicide Sunstar 15WG （ethoxy sulfuron）, Machete 60EC （butachlor）, conventional hand weeding, and the weedy check （control） were assigned to the sub-plots. Data were recorded on weed parameters like weed density and dry weed biomass 60 and 90 days after sowing （DAS）; agronomic parameters including plant population, number of panicles and paddy yield and physiological parameters like leaf area index and net assimilation rate 45 and 90 DAS. The planting methods and weed management significantly influenced most of the parameters studied. The data revealed that the paddy yield and its components were significantly higher in the transplanted method than that in direct-seeded method, while the weed density and biomass were lower in the transplanted plots than the direct-seeded plots. Among weed management tools, the maximum paddy yield was obtained in hand weeding, closely followed by herbicide application Machete 60EC during both cropping seasons.展开更多
Competition between crops and weeds interfere on growth and development with harm to one or both, in different ways. To quantify these differences in competition, additive and replacement series study methods are most...Competition between crops and weeds interfere on growth and development with harm to one or both, in different ways. To quantify these differences in competition, additive and replacement series study methods are most often used, each with different characteristics and goals. Therefore, we aimed with this work to study inter-specific competition between plants of soybean and corn against the weeds Bidens pilosa (beggartick) and Digitaria insularis (sourgrass), by two experimental methods of study: additive and replacement series (substitutive) experiments. Initial tests were performed prior to the installation of replacement series experiments to describe the intra-specific competition features for all species. For additive experiments these are unnecessary. To compare the methods of study, there were two sets of trials (an additive and a substitutive) installed under greenhouse, during the growing season 2013/14. Variables analyzed were leaf area and dry weight of shoots of crops and weeds, at 50 days after emergence. The results were analyzed according to the methods used, these being compared. It was found that the additive method supplied results most prone to be applied in the field, while the replacement series (substitutive) method was more appropriate for studies that aimed to provide detailed scientific information regarding the proportions of plants and coefficients describing the behavior of the species community.展开更多
Weeds cause significant production losses estimated at 25%in tropical countries and constitute main factor limiting rice production in Madagascar.This research,which was conducted at Anosibe-Ifanja(Antananarivo,Madaga...Weeds cause significant production losses estimated at 25%in tropical countries and constitute main factor limiting rice production in Madagascar.This research,which was conducted at Anosibe-Ifanja(Antananarivo,Madagascar),aims to propose the most cost-effective weed management strategies for both irrigated and rainfed rice system to improve rice production.To make the management of these potential rice weeds effective,two cultural practices were tested as good agricultural and farmers’practices on two rice systems.A phytoecological study and a floristic inventory were carried out on test plots,followed by an economic profitability analysis of management strategies.In rainfed rice,a greater number of species were inventoried(42 species in 14 families)than in irrigated rice(37 species in 9 families).The most important families found in both systems were Poaceae and Cyperaceae.But in rainfed rice,two other families are also dominant:Fabaceae and Asteraceae.The study on weed management strategy showed that adoption of in-season and out-of-season tillage combined with regular weeding is effective for weed control in irrigated rice.As far as rainfed rice is concerned,improved farming practice by integrating in-season tillage with aerial ploughing combined with the use of pre-emergence herbicide pendimethalin is more cost-effective.This research has resulted in an in-depth knowledge of rice weeds and weed control strategies that are only feasible with mechanization or animal traction.展开更多
We aimed with this study to evaluate the potential of oilseed crops planted following soybean, in terms of their ability to inhibit the occurrence of weed species under Brazilian Savannah cropping systems. The long-te...We aimed with this study to evaluate the potential of oilseed crops planted following soybean, in terms of their ability to inhibit the occurrence of weed species under Brazilian Savannah cropping systems. The long-term experiment was installed in 2010 at Dourados, MS, Brazil, and in completely randomized blocks design with five replications with 12 × 24 m plot size. For three consecutive years (2010/11, 2011/12 and 2012/13), soybeans were planted in all the area by October/November being harvested in February/March, when previously marked plots were planted in April with: (1) radish (Raphanus sativus);(2) rapeseed (Brassica napus);(3) crambe (Crambe abyssinica);(4) winter fallow-no plantation after soybeans. In all years the same crop was repeated at the same plots, with no crop rotation. Phytosociological characterization of weed species was carried out in winter (after oilseeds harvest), pre-planting and post-emergence of soybean for the three years. Relative abundance, frequency and dominance, as well as the importance value for each species, was obtained. Areas were also intra-characterized by the coefficients of Simpson, Shannon-Weiner and Shannon-Weiner’s Evenness Proportion, and areas were compared for species dissimilarity with Jaccard’s presence-only coefficient, by multivariate cluster analysis. Oilseed crops definitely contribute for sustainable weed management as a cultural tool. The most important oilseed crop weeds in the Savannah-like region of Brazil were Amaranthus hybridus, Richardia brasiliensis, Lepidium virginicum, Leonotis nepetifolia and Hybanthus parviflorus. After three years of repetitive crop succession, some weeds were selected, and rotation in Winter is advised at least every two or three years.展开更多
Weeds, which cause loss of more than half of production, constitute one of obstacles to development of agriculturalproduction in Madagascar. This study aimed to characterize weed flora and to analyze constraint of wee...Weeds, which cause loss of more than half of production, constitute one of obstacles to development of agriculturalproduction in Madagascar. This study aimed to characterize weed flora and to analyze constraint of weeding irrigated rice with aview to improve control strategy. A phytoecological study of weeds was carried out during 2018-2019 season, on 125 rice plots withan average area of 500 m², in Anosibe Ifanja, Middle-West region of Madagascar (18°52′ S and 46°50′ E). Surveys on croppingpractices and observations on rice field ecology and the importance of weed cover level were carried out in order to establishrelationship between factors affecting diversity, distribution and level of weed infestation in rice field. As a result, 47 weed speciesgrouped into about 20 families were identified. Weed cover quantification in each plot, permits to distinguish three major importancespecies, including Junglerice - Echinochloa colona (Poaceae), Tail - Leersia hexandra (Oryzoideae), saramollagrass - Ischaemumrugosum (Poaceae) and hemp sesbania - Sesbania rostrata (Fabaceae). Analysis of agro-ecological factors showed that all productiontechniques and growing conditions have a role to play in variability of plant cover level. Thus, the main production factors thatvegetation cover reduce state are ploughing to a depth of 30 cm, practice of ploughing off-season/in-season and good water control.Ecological factors, especially soil type, soil structure and topography, minimize weed cover in rice fields.展开更多
Chemical and physical mutagenesis has been used to increase genetic variability in crop plants. More than 430 new varieties have been derived as mutants of rice (Oryza sativa L.) via the application of different mutag...Chemical and physical mutagenesis has been used to increase genetic variability in crop plants. More than 430 new varieties have been derived as mutants of rice (Oryza sativa L.) via the application of different mutagenic agents. Chemical mutagens such as ethyl methane sulphonate (EMS), diepoxybutane-derived (DEB), sodium azide and irradiation (Gamma rays, X-rays and fast neutrons) have been widely used to induce a large number of functional variations in rice and others crops. Among chemical mutagens, the alkylating agent, ethyl methane sulfonate (EMS) is the most commonly used in plants as it causes a high frequency of nucleotide substitutions, as detected in different genomes. In this study, seeds of potential genotype of the popular variety, (Oryza sativa L. spp. Indica cv. MR219) were treated with EMS at concentrations of 0.25%, 0.50%, 0.75%, 1%, 1.25%, 1.5% and 2%. Sensitivity to EMS was determined by various measurements on the M1 generation. As concentration of applied EMS increased, will decrease in germination, seedling height, root length and emergence under field conditions was observed in M1 generation as compared to the non-treatment control. Plant height and root length also decreased with increases in EMS mutagenesis in an approximately linear fashion. The LD25 and LD50 values were observed based on growth reduction of seedlings after EMS treatment with 0.25% and 0.50% on the rice variety (Oryza sativa L. spp. Indica cv. MR219).展开更多
Studies were initiated for two consecutive years to find out the effect of time of transplanting and seedlings hill^-l on the productivity of rice in Dera Ismail Khan district of North West Frontier Province （NWFP）,...Studies were initiated for two consecutive years to find out the effect of time of transplanting and seedlings hill^-l on the productivity of rice in Dera Ismail Khan district of North West Frontier Province （NWFP）, Pakistan. The experiment was laid out in a randomized complete block design with split plot arrangements. Main plots consisted of four transplanting dates viz. 20th and 27th of June and 4th and 1 lth of July while sub-plots contained 1, 2, 3 or 4 seedlings hill^-1. Among transplanting dates, June 20th planted crop gave highest paddy yield and net return with I seedling hill^-1. It explains that the use of more seedlings hill^-1 not only adds to cost but is also a mere wastage of natural resources. Based on research findings, we conclude that the use of I seedling hill^-1 is most appropriate for timely sowing otherwise 4 seedlings hill^-1 should be used to compensate for the yield gap in late transplanted rice.展开更多
This study was conducted with the aim of finding humic acid and crop residues effects on soil and wheat nitrogen at New Development Farm, University of Agriculture, Peshawar, Pakistan during winter 2009-2010. The expe...This study was conducted with the aim of finding humic acid and crop residues effects on soil and wheat nitrogen at New Development Farm, University of Agriculture, Peshawar, Pakistan during winter 2009-2010. The experiment was laid out in RCB design having four replications. Different levels (1, 1.5, 2 and 2.5 kg ha-1) of Humic acid were applied at sowing time. Mungbean (5 tons ha-1), wheat straw (10 tons ha-1) and mungbean (2.5 tons ha-1) + wheat straw (5 tons ha-1) were incorporated 30 days before sowing. Our results showed higher mineral and total nitrogen (7.32 and 0.43, respectively) mg kg-1 in soil and also higher nitrogen in stem, leaves and grains (2.3, 4.6 and 21.1, respectively) mg kg-1 at maturity in those plots in which 2.5 kg ha-1 of humic acid was applied. Higher mineral and total nitrogen (7.04 and 0.5, respectively) mg kg-1 in soil and also higher nitrogen in leaves (5.5) mg kg-1 at pre-anthesis, while at maturity stage in stem, leaves and grain (5.5, 2.1, 4.2 and 20.8) g kg-1 was recorded in those plots in which 5 tons ha-1 mung bean was incorporated. Our experimental results suggest the use of 5 tons ha-1 of mungbean residues with 2.5 kg ha-1 of humic acid to improve soil fertility availability of more nitrogen in wheat plants to increase the crop yield and grains quality.展开更多
Effects of sub-millimeter scale heterogeneity in chemical and microbial distributions on atrazine degradation were examined using Pseudomonas sp. strain ADP introduced into soil at a population mimicking atrazine-adap...Effects of sub-millimeter scale heterogeneity in chemical and microbial distributions on atrazine degradation were examined using Pseudomonas sp. strain ADP introduced into soil at a population mimicking atrazine-adapted soils (~2000 cells/g), and employing a range of soil water pressures (?100, ?300, ?500 kPa). Heterogeneous cell distribution was employed in all treatments whereas uniformity of distribution was a variable for atrazine introduction. Two methods of initially distributing atrazine in soil were examined. Proximally-applied atrazine (PAA) was intended to yield elevated atrazine concentrations in the vicinity of the degraders. Dispersed atrazine (DA) was introduced to distribute the chemical uniformly as compared to the distribution of degraders. Both rate and extent of degradation were greater than PAA, regardless of water content, presumably due to proximity of atrazine to degraders. Biodegradation decreased with decreasing water content for both application methods, attributed to decreases in atrazine’s effective diffusion. Mineralization of nearly 100% of DA in soils receiving a heterogeneous inoculum with a greater cell density (~107 cells/g) indicates that biodegradation was limited by the distance atrazine had to diffuse. Results support the hypothesis that enhanced populations of atrazine degraders, as reported elsewhere for atrazine-adapted soils, though heterogeneously distributed, may overcome bioavailability limitations.展开更多
Exserohilum monoceras （Drechsler） Leonard and Suggs is a potential biocontrol agent for the control of Echinochloa species. This fungus causes leaf blight in Echinochloa species, but does not damage rice. Phytotoxic...Exserohilum monoceras （Drechsler） Leonard and Suggs is a potential biocontrol agent for the control of Echinochloa species. This fungus causes leaf blight in Echinochloa species, but does not damage rice. Phytotoxicity of the fungal fermented broth was evaluated through the bioassay and the active ingredients were preliminarily isolated by using silica gel column chromatography （CC） in this study. The most active fraction 5-Ⅲ was obtained and analyzed by gas chromatography-mass spectrometry （GC-MS）. The results show that 5-Ⅲ consisted of many compounds, in which 36 compounds accounted for 94.24% of total peak area. Di-n-butyl phthalate （DBP） displayed the highest activity accounted for 9.24% of the total peak area, suggesting that DBP may be one of the main active compounds produced by E. monoceras.展开更多
This experiment was conducted to study the effect of foliar spray of micronutrients on quality of peach fruits at Horticulture Farm, University of Agriculture Peshawar during 2010. The experiment was conducted in rand...This experiment was conducted to study the effect of foliar spray of micronutrients on quality of peach fruits at Horticulture Farm, University of Agriculture Peshawar during 2010. The experiment was conducted in randomized complete design with six treatments and four replications on peach orchards (early grand). Our pre-treatment soil analysis showed silt loam soil class, alkaline and calcareous in nature and adequate in organic matter. The soil was deficient in P, Zn, Fe and B, whereas adequate in Mn and Cu. The fruit quality was evaluated and maximum fruit length, diameter and yield were noted in T6 (Zn + Cu + Fe + Mn + B). The juice pH decreased and the juice acidity increased in a linear fashion after foliar spray of micronutrients. The total soluble solids of fresh fruit juice ranged 7.01%-8.88% and vitamin C ranged from 4.80%-7.90% after foliar spray. So the foliar spray of micronutrients significantly (P ≤ 0.05) affected the quality of peach fruit.展开更多
One of the main reasons behind reduced cane yield is pathetic method of planting. Planting method and row spacing are the most important yield contributing factors in sugarcane. A field experiment was carried out in o...One of the main reasons behind reduced cane yield is pathetic method of planting. Planting method and row spacing are the most important yield contributing factors in sugarcane. A field experiment was carried out in order to determine quality and yield of sugarcane in various spatial arrangements. Treatments are 180 cm spaced trenches with triple row strips;180 cm spaced trenches with alternate row strips;120 cm spaced trenches with double row strips and 60 cm spaced furrow with single row. Perusal of data revealed that 3.6%, 13.4%, 15%, 15.3% more cane diameter (cm), cane length (cm), stripped cane yield (t·haˉ1</sup>), sugar yield (t·haˉ1</sup>) were obtained from 180 cm spaced trenches with triple row strips as compared to conventional planting method i.e. 60 cm spaced furrows. While the number of millable canes mˉ2</sup>, polarity %, cane juice purity %, cane juice %, commercial cane sugar % and cane sugar recovery % remained non-significant by different planting techniques.展开更多
Guar is a drought and salt tolerant summer annual legume, which could be a potential alternative crop in the semi-arid Southern High Plains. Increased use of guar gum in oil industries has increased the demand of guar...Guar is a drought and salt tolerant summer annual legume, which could be a potential alternative crop in the semi-arid Southern High Plains. Increased use of guar gum in oil industries has increased the demand of guar globally. Planting date effects on stand establishment, physiological parameters, and yield formation of guar genotypes were investigated at the New Mexico State University’s Agricultural Science Center at Clovis, NM for two seasons (2014 and 2015). Four guar genotypes (HES 1123, Kinman, Lewis, and Matador) were tested under three planting dates (June 18, July 7, and July 22 in 2014;and June 18, July 6, and July 20 in 2015). Higher temperature and rainfall were recorded under mid-June planting than early-July and late-July plantings. Guar planted under mid-June had better stand establishment as shown by the higher number of plants m<sup>-2</sup>, better physiology as revealed by higher photosynthetic rate (P<sub>n</sub>), transpiration rate (T<sub>r</sub>), leaf area index (LAI), and SPAD values than early-July and late-July plantings. Guar planted under mid-June resulted in taller plants, and therefore, produced higher plant biomass than both of the July plantings. Yield attributing characteristics including clusters plant<sup>-1</sup>, pods plant<sup>-1</sup>, seeds plant<sup>-1</sup>, seed spod<sup>-1</sup>, 1000 seed weight, and harvest index (HI) were highest under mid-June planting followed by the early-July and late-July plantings, respectively. The mid-June planting increased seed yield by 26% and 55% over early-July and late-July (1399 vs. 1111 and 903 kg·ha<sup>-1</sup>) plantings, respectively in 2014;while the same increase in 2015 was 51% and 243% (1308 vs. 868 and 381 kg·ha<sup>-1</sup>), respectively. These results indicate that delaying planting beyond mid-June is detrimental to guar productivity. However, genotypes did not show any significant variation in their performance. Overall, warmer growing conditions and more precipitation under mid-June planting caused better growth and yield formation of guar genotypes.展开更多
Strigolactones are plant hormones with multiple functions, including regulating various aspects of plant architecture such as shoot branching, facilitating the colonization of plant roots by arbuscular mycorrhizal fun...Strigolactones are plant hormones with multiple functions, including regulating various aspects of plant architecture such as shoot branching, facilitating the colonization of plant roots by arbuscular mycorrhizal fungi, and acting as seed germination stimulants for certain parasitic plants of the family Orobanchaceae. The obligate parasitic species Phelipanche aegyptiaca and Striga hermonthica require strigolactones for germination, while the facultative parasite Triphysaria versicolor does not. It has been hypothesized that P. aegyptiaca and S. hermonthica would have undergone evolutionary loss of strigolactone biosynthesis as a part of their mechanism to enable specific detection of exogenous strigolactones. We analyzed the transcriptomes of P. aegyptiaca, S. hermonthica and T. versicolor and identified genes known to act in strigolactone synthesis (D27, CCD7, CCD8, and MAX1), perception (MAX2 and D14) and transport (PDR12). These genes were then analyzed to assess likelihood of function. Transcripts of all strigolactone-related genes were found in P. aegyptiaca and S. hermonthica, and evidence points to their encoding functional proteins. Gene open reading frames were consistent with homologs from Arabidopsis and other strigolactone-producing plants, and all genes were expressed in parasite tissues. In general, the genes related to strigolactone synthesis and perception appeared to be evolving under codon-based selective constraints in strigolactone-dependent species. Bioassays of S. hermonthica root extracts indicated the presence of strigolactone class stimulants on germination of P. aegyptiaca seeds. Taken together, these results indicate that Phelipanche aegyptiaca and S. hermonthica have retained functional genes involved in strigolactone biosynthesis, suggesting that the parasites use both endogenous and exogenous strigolactones and have mechanisms to differentiate the two.展开更多
A collection representing the native range of pecan was planted at the US DA-ARS Southeastern Fruit and Tree Nut Research Station,Byron,GA.The collection(867 trees)is a valuable genetic resource for characterizing imp...A collection representing the native range of pecan was planted at the US DA-ARS Southeastern Fruit and Tree Nut Research Station,Byron,GA.The collection(867 trees)is a valuable genetic resource for characterizing important horticultural traits.Canopy density during leaf fall is important as the seasonal canopy dynamics provides insights to environmental cues and breeding potential of germplasm.The ability of visual raters to estimate canopy density on a subset of the provenance collection(76 trees)as an indicator of leaf shed during autumn along with image analysis values was explored.Mean canopy density using the image analysis software was less compared to visual estimates(11.9%vs 18.4%,respectively).At higher canopy densities,the raters overestimated foliage density,but overall agreement between raters and measured values was good(ρc=0.849 to 0.915),and inter-rater reliability was high(R^(2)=0.910 to 0.953).The provenance from Missouri(MOL),the northernmost provenance,had the lowest canopy density in November,and results show that the higher the latitude of the provenance,the lower the canopy density.Based on regression,the source provenance latitude explained 0.609 of the variation using image analysis,and0.551 to 0.640 when based on the rater estimates of canopy density.Visual assessment of pecan canopy density due to late season leaf fall for comparing pecan genotypes provides accurate and reliable estimates and could be used in future studies of the whole provenance collection.展开更多
Rice production in Pakistan is constraint by many factors pertaining to prevalent planting techniques. A research on the feasibility of new planting techniques （direct seeding on flat, transplanting on flat, direct s...Rice production in Pakistan is constraint by many factors pertaining to prevalent planting techniques. A research on the feasibility of new planting techniques （direct seeding on flat, transplanting on flat, direct seeding on ridges, transplanting on ridges and parachute planting） in transplanted and direct wet-seeded rice was undertaken at Dera Ismail Khan region of Pakistan＇s North West Frontier Province during 2002 and 2003. Among the planting techniques, the best performance for the yield formation and economic evaluation was noted for transplanting on flat during both years. Chinese parachute planting technology also showed very promising results in most of the parameters. Direct seeding on ridges could not excel transplanting on flat and parachute planting during both cropping seasons. The findings concluded the feasibility of parachute planting technology along with traditional rice transplanting on flat over all other planting techniques being practiced in the area.展开更多
Chemical control is presently the most cost-effective means to control kudzu;however, some of the herbicides labeled for kudzu control have substantial non-target toxicity, poor selectivity, high cost, long soil persi...Chemical control is presently the most cost-effective means to control kudzu;however, some of the herbicides labeled for kudzu control have substantial non-target toxicity, poor selectivity, high cost, long soil persistence, high soil mobility and/or high use rates. The present study evaluated other herbicides for efficacy in suppressing aboveground kudzu biomass in replicated field trials at three sites over two years. A single application of aminopyralid, triclopyr or metsulfuron resulted in at least 90% kudzu suppression in the following season at two locations. After a second year of treatment those herbicides and fluroxypyr produced at least 90% kudzu suppression, and 100% kudzu control was reached on some test plots. Glyphosate, glufosinate and mesotrione were less effective in controlling kudzu. Given the rapid growth potential of kudzu, complete eradication should be pursued. None of the herbicides evaluated in the present study could reliably achieve eradication of mature kudzu with two applications, so additional control efforts would be required.展开更多
Weeds pose a significant threat to crop production,resulting in substantial yield reduction.In addition,they possess robust weedy traits that enable them to survive in extreme environments and evade human con-trol.In ...Weeds pose a significant threat to crop production,resulting in substantial yield reduction.In addition,they possess robust weedy traits that enable them to survive in extreme environments and evade human con-trol.In recent years,the application of multi-omics biotechnologies has helped to reveal the molecular mechanisms underlying these weedy traits.In this review,we systematically describe diverse applications of multi-omics platforms for characterizing key aspects of weed biology,including the origins of weed spe-cies,weed classification,and the underlying genetic and molecular bases of important weedy traits such as crop–weed interactions,adaptability to different environments,photoperiodicflowering responses,and herbicide resistance.In addition,we discuss limitations to the application of multi-omics techniques in weed science,particularly compared with their extensive use in model plants and crops.In this regard,we provide a forward-looking perspective on the future application of multi-omics technologies to weed science research.These powerful tools hold great promise for comprehensively and efficiently unraveling the intricate molecular genetic mechanisms that underlie weedy traits.The resulting advances will facilitate the development of sustainable and highly effective weed management strategies,promoting greener practices in agriculture.展开更多
文摘Studies were carried out for two years to evaluate the effect of methods of sowing and weed control practices on the productivity of transplanted and direct wet-seeded rice in Dera Ismail Khan, NWFP, Pakistan. The experiment was laid out in a randomized complete block design with a split plot arrangement. The planting techniques viz. transplanting and direct seeding were maintained in main plots while weed control practices included the use of granular herbicide Sunstar 15WG （ethoxy sulfuron）, Machete 60EC （butachlor）, conventional hand weeding, and the weedy check （control） were assigned to the sub-plots. Data were recorded on weed parameters like weed density and dry weed biomass 60 and 90 days after sowing （DAS）; agronomic parameters including plant population, number of panicles and paddy yield and physiological parameters like leaf area index and net assimilation rate 45 and 90 DAS. The planting methods and weed management significantly influenced most of the parameters studied. The data revealed that the paddy yield and its components were significantly higher in the transplanted method than that in direct-seeded method, while the weed density and biomass were lower in the transplanted plots than the direct-seeded plots. Among weed management tools, the maximum paddy yield was obtained in hand weeding, closely followed by herbicide application Machete 60EC during both cropping seasons.
文摘Competition between crops and weeds interfere on growth and development with harm to one or both, in different ways. To quantify these differences in competition, additive and replacement series study methods are most often used, each with different characteristics and goals. Therefore, we aimed with this work to study inter-specific competition between plants of soybean and corn against the weeds Bidens pilosa (beggartick) and Digitaria insularis (sourgrass), by two experimental methods of study: additive and replacement series (substitutive) experiments. Initial tests were performed prior to the installation of replacement series experiments to describe the intra-specific competition features for all species. For additive experiments these are unnecessary. To compare the methods of study, there were two sets of trials (an additive and a substitutive) installed under greenhouse, during the growing season 2013/14. Variables analyzed were leaf area and dry weight of shoots of crops and weeds, at 50 days after emergence. The results were analyzed according to the methods used, these being compared. It was found that the additive method supplied results most prone to be applied in the field, while the replacement series (substitutive) method was more appropriate for studies that aimed to provide detailed scientific information regarding the proportions of plants and coefficients describing the behavior of the species community.
文摘Weeds cause significant production losses estimated at 25%in tropical countries and constitute main factor limiting rice production in Madagascar.This research,which was conducted at Anosibe-Ifanja(Antananarivo,Madagascar),aims to propose the most cost-effective weed management strategies for both irrigated and rainfed rice system to improve rice production.To make the management of these potential rice weeds effective,two cultural practices were tested as good agricultural and farmers’practices on two rice systems.A phytoecological study and a floristic inventory were carried out on test plots,followed by an economic profitability analysis of management strategies.In rainfed rice,a greater number of species were inventoried(42 species in 14 families)than in irrigated rice(37 species in 9 families).The most important families found in both systems were Poaceae and Cyperaceae.But in rainfed rice,two other families are also dominant:Fabaceae and Asteraceae.The study on weed management strategy showed that adoption of in-season and out-of-season tillage combined with regular weeding is effective for weed control in irrigated rice.As far as rainfed rice is concerned,improved farming practice by integrating in-season tillage with aerial ploughing combined with the use of pre-emergence herbicide pendimethalin is more cost-effective.This research has resulted in an in-depth knowledge of rice weeds and weed control strategies that are only feasible with mechanization or animal traction.
文摘We aimed with this study to evaluate the potential of oilseed crops planted following soybean, in terms of their ability to inhibit the occurrence of weed species under Brazilian Savannah cropping systems. The long-term experiment was installed in 2010 at Dourados, MS, Brazil, and in completely randomized blocks design with five replications with 12 × 24 m plot size. For three consecutive years (2010/11, 2011/12 and 2012/13), soybeans were planted in all the area by October/November being harvested in February/March, when previously marked plots were planted in April with: (1) radish (Raphanus sativus);(2) rapeseed (Brassica napus);(3) crambe (Crambe abyssinica);(4) winter fallow-no plantation after soybeans. In all years the same crop was repeated at the same plots, with no crop rotation. Phytosociological characterization of weed species was carried out in winter (after oilseeds harvest), pre-planting and post-emergence of soybean for the three years. Relative abundance, frequency and dominance, as well as the importance value for each species, was obtained. Areas were also intra-characterized by the coefficients of Simpson, Shannon-Weiner and Shannon-Weiner’s Evenness Proportion, and areas were compared for species dissimilarity with Jaccard’s presence-only coefficient, by multivariate cluster analysis. Oilseed crops definitely contribute for sustainable weed management as a cultural tool. The most important oilseed crop weeds in the Savannah-like region of Brazil were Amaranthus hybridus, Richardia brasiliensis, Lepidium virginicum, Leonotis nepetifolia and Hybanthus parviflorus. After three years of repetitive crop succession, some weeds were selected, and rotation in Winter is advised at least every two or three years.
文摘Weeds, which cause loss of more than half of production, constitute one of obstacles to development of agriculturalproduction in Madagascar. This study aimed to characterize weed flora and to analyze constraint of weeding irrigated rice with aview to improve control strategy. A phytoecological study of weeds was carried out during 2018-2019 season, on 125 rice plots withan average area of 500 m², in Anosibe Ifanja, Middle-West region of Madagascar (18°52′ S and 46°50′ E). Surveys on croppingpractices and observations on rice field ecology and the importance of weed cover level were carried out in order to establishrelationship between factors affecting diversity, distribution and level of weed infestation in rice field. As a result, 47 weed speciesgrouped into about 20 families were identified. Weed cover quantification in each plot, permits to distinguish three major importancespecies, including Junglerice - Echinochloa colona (Poaceae), Tail - Leersia hexandra (Oryzoideae), saramollagrass - Ischaemumrugosum (Poaceae) and hemp sesbania - Sesbania rostrata (Fabaceae). Analysis of agro-ecological factors showed that all productiontechniques and growing conditions have a role to play in variability of plant cover level. Thus, the main production factors thatvegetation cover reduce state are ploughing to a depth of 30 cm, practice of ploughing off-season/in-season and good water control.Ecological factors, especially soil type, soil structure and topography, minimize weed cover in rice fields.
文摘Chemical and physical mutagenesis has been used to increase genetic variability in crop plants. More than 430 new varieties have been derived as mutants of rice (Oryza sativa L.) via the application of different mutagenic agents. Chemical mutagens such as ethyl methane sulphonate (EMS), diepoxybutane-derived (DEB), sodium azide and irradiation (Gamma rays, X-rays and fast neutrons) have been widely used to induce a large number of functional variations in rice and others crops. Among chemical mutagens, the alkylating agent, ethyl methane sulfonate (EMS) is the most commonly used in plants as it causes a high frequency of nucleotide substitutions, as detected in different genomes. In this study, seeds of potential genotype of the popular variety, (Oryza sativa L. spp. Indica cv. MR219) were treated with EMS at concentrations of 0.25%, 0.50%, 0.75%, 1%, 1.25%, 1.5% and 2%. Sensitivity to EMS was determined by various measurements on the M1 generation. As concentration of applied EMS increased, will decrease in germination, seedling height, root length and emergence under field conditions was observed in M1 generation as compared to the non-treatment control. Plant height and root length also decreased with increases in EMS mutagenesis in an approximately linear fashion. The LD25 and LD50 values were observed based on growth reduction of seedlings after EMS treatment with 0.25% and 0.50% on the rice variety (Oryza sativa L. spp. Indica cv. MR219).
文摘Studies were initiated for two consecutive years to find out the effect of time of transplanting and seedlings hill^-l on the productivity of rice in Dera Ismail Khan district of North West Frontier Province （NWFP）, Pakistan. The experiment was laid out in a randomized complete block design with split plot arrangements. Main plots consisted of four transplanting dates viz. 20th and 27th of June and 4th and 1 lth of July while sub-plots contained 1, 2, 3 or 4 seedlings hill^-1. Among transplanting dates, June 20th planted crop gave highest paddy yield and net return with I seedling hill^-1. It explains that the use of more seedlings hill^-1 not only adds to cost but is also a mere wastage of natural resources. Based on research findings, we conclude that the use of I seedling hill^-1 is most appropriate for timely sowing otherwise 4 seedlings hill^-1 should be used to compensate for the yield gap in late transplanted rice.
文摘This study was conducted with the aim of finding humic acid and crop residues effects on soil and wheat nitrogen at New Development Farm, University of Agriculture, Peshawar, Pakistan during winter 2009-2010. The experiment was laid out in RCB design having four replications. Different levels (1, 1.5, 2 and 2.5 kg ha-1) of Humic acid were applied at sowing time. Mungbean (5 tons ha-1), wheat straw (10 tons ha-1) and mungbean (2.5 tons ha-1) + wheat straw (5 tons ha-1) were incorporated 30 days before sowing. Our results showed higher mineral and total nitrogen (7.32 and 0.43, respectively) mg kg-1 in soil and also higher nitrogen in stem, leaves and grains (2.3, 4.6 and 21.1, respectively) mg kg-1 at maturity in those plots in which 2.5 kg ha-1 of humic acid was applied. Higher mineral and total nitrogen (7.04 and 0.5, respectively) mg kg-1 in soil and also higher nitrogen in leaves (5.5) mg kg-1 at pre-anthesis, while at maturity stage in stem, leaves and grain (5.5, 2.1, 4.2 and 20.8) g kg-1 was recorded in those plots in which 5 tons ha-1 mung bean was incorporated. Our experimental results suggest the use of 5 tons ha-1 of mungbean residues with 2.5 kg ha-1 of humic acid to improve soil fertility availability of more nitrogen in wheat plants to increase the crop yield and grains quality.
文摘Effects of sub-millimeter scale heterogeneity in chemical and microbial distributions on atrazine degradation were examined using Pseudomonas sp. strain ADP introduced into soil at a population mimicking atrazine-adapted soils (~2000 cells/g), and employing a range of soil water pressures (?100, ?300, ?500 kPa). Heterogeneous cell distribution was employed in all treatments whereas uniformity of distribution was a variable for atrazine introduction. Two methods of initially distributing atrazine in soil were examined. Proximally-applied atrazine (PAA) was intended to yield elevated atrazine concentrations in the vicinity of the degraders. Dispersed atrazine (DA) was introduced to distribute the chemical uniformly as compared to the distribution of degraders. Both rate and extent of degradation were greater than PAA, regardless of water content, presumably due to proximity of atrazine to degraders. Biodegradation decreased with decreasing water content for both application methods, attributed to decreases in atrazine’s effective diffusion. Mineralization of nearly 100% of DA in soils receiving a heterogeneous inoculum with a greater cell density (~107 cells/g) indicates that biodegradation was limited by the distance atrazine had to diffuse. Results support the hypothesis that enhanced populations of atrazine degraders, as reported elsewhere for atrazine-adapted soils, though heterogeneously distributed, may overcome bioavailability limitations.
基金the National Natural Science Foundation of China(30671381,30671381)Guangdong Provincial Natural Science Foundation of China(06300411)for the financial supports
文摘Exserohilum monoceras （Drechsler） Leonard and Suggs is a potential biocontrol agent for the control of Echinochloa species. This fungus causes leaf blight in Echinochloa species, but does not damage rice. Phytotoxicity of the fungal fermented broth was evaluated through the bioassay and the active ingredients were preliminarily isolated by using silica gel column chromatography （CC） in this study. The most active fraction 5-Ⅲ was obtained and analyzed by gas chromatography-mass spectrometry （GC-MS）. The results show that 5-Ⅲ consisted of many compounds, in which 36 compounds accounted for 94.24% of total peak area. Di-n-butyl phthalate （DBP） displayed the highest activity accounted for 9.24% of the total peak area, suggesting that DBP may be one of the main active compounds produced by E. monoceras.
文摘This experiment was conducted to study the effect of foliar spray of micronutrients on quality of peach fruits at Horticulture Farm, University of Agriculture Peshawar during 2010. The experiment was conducted in randomized complete design with six treatments and four replications on peach orchards (early grand). Our pre-treatment soil analysis showed silt loam soil class, alkaline and calcareous in nature and adequate in organic matter. The soil was deficient in P, Zn, Fe and B, whereas adequate in Mn and Cu. The fruit quality was evaluated and maximum fruit length, diameter and yield were noted in T6 (Zn + Cu + Fe + Mn + B). The juice pH decreased and the juice acidity increased in a linear fashion after foliar spray of micronutrients. The total soluble solids of fresh fruit juice ranged 7.01%-8.88% and vitamin C ranged from 4.80%-7.90% after foliar spray. So the foliar spray of micronutrients significantly (P ≤ 0.05) affected the quality of peach fruit.
文摘One of the main reasons behind reduced cane yield is pathetic method of planting. Planting method and row spacing are the most important yield contributing factors in sugarcane. A field experiment was carried out in order to determine quality and yield of sugarcane in various spatial arrangements. Treatments are 180 cm spaced trenches with triple row strips;180 cm spaced trenches with alternate row strips;120 cm spaced trenches with double row strips and 60 cm spaced furrow with single row. Perusal of data revealed that 3.6%, 13.4%, 15%, 15.3% more cane diameter (cm), cane length (cm), stripped cane yield (t·haˉ1</sup>), sugar yield (t·haˉ1</sup>) were obtained from 180 cm spaced trenches with triple row strips as compared to conventional planting method i.e. 60 cm spaced furrows. While the number of millable canes mˉ2</sup>, polarity %, cane juice purity %, cane juice %, commercial cane sugar % and cane sugar recovery % remained non-significant by different planting techniques.
文摘Guar is a drought and salt tolerant summer annual legume, which could be a potential alternative crop in the semi-arid Southern High Plains. Increased use of guar gum in oil industries has increased the demand of guar globally. Planting date effects on stand establishment, physiological parameters, and yield formation of guar genotypes were investigated at the New Mexico State University’s Agricultural Science Center at Clovis, NM for two seasons (2014 and 2015). Four guar genotypes (HES 1123, Kinman, Lewis, and Matador) were tested under three planting dates (June 18, July 7, and July 22 in 2014;and June 18, July 6, and July 20 in 2015). Higher temperature and rainfall were recorded under mid-June planting than early-July and late-July plantings. Guar planted under mid-June had better stand establishment as shown by the higher number of plants m<sup>-2</sup>, better physiology as revealed by higher photosynthetic rate (P<sub>n</sub>), transpiration rate (T<sub>r</sub>), leaf area index (LAI), and SPAD values than early-July and late-July plantings. Guar planted under mid-June resulted in taller plants, and therefore, produced higher plant biomass than both of the July plantings. Yield attributing characteristics including clusters plant<sup>-1</sup>, pods plant<sup>-1</sup>, seeds plant<sup>-1</sup>, seed spod<sup>-1</sup>, 1000 seed weight, and harvest index (HI) were highest under mid-June planting followed by the early-July and late-July plantings, respectively. The mid-June planting increased seed yield by 26% and 55% over early-July and late-July (1399 vs. 1111 and 903 kg·ha<sup>-1</sup>) plantings, respectively in 2014;while the same increase in 2015 was 51% and 243% (1308 vs. 868 and 381 kg·ha<sup>-1</sup>), respectively. These results indicate that delaying planting beyond mid-June is detrimental to guar productivity. However, genotypes did not show any significant variation in their performance. Overall, warmer growing conditions and more precipitation under mid-June planting caused better growth and yield formation of guar genotypes.
文摘Strigolactones are plant hormones with multiple functions, including regulating various aspects of plant architecture such as shoot branching, facilitating the colonization of plant roots by arbuscular mycorrhizal fungi, and acting as seed germination stimulants for certain parasitic plants of the family Orobanchaceae. The obligate parasitic species Phelipanche aegyptiaca and Striga hermonthica require strigolactones for germination, while the facultative parasite Triphysaria versicolor does not. It has been hypothesized that P. aegyptiaca and S. hermonthica would have undergone evolutionary loss of strigolactone biosynthesis as a part of their mechanism to enable specific detection of exogenous strigolactones. We analyzed the transcriptomes of P. aegyptiaca, S. hermonthica and T. versicolor and identified genes known to act in strigolactone synthesis (D27, CCD7, CCD8, and MAX1), perception (MAX2 and D14) and transport (PDR12). These genes were then analyzed to assess likelihood of function. Transcripts of all strigolactone-related genes were found in P. aegyptiaca and S. hermonthica, and evidence points to their encoding functional proteins. Gene open reading frames were consistent with homologs from Arabidopsis and other strigolactone-producing plants, and all genes were expressed in parasite tissues. In general, the genes related to strigolactone synthesis and perception appeared to be evolving under codon-based selective constraints in strigolactone-dependent species. Bioassays of S. hermonthica root extracts indicated the presence of strigolactone class stimulants on germination of P. aegyptiaca seeds. Taken together, these results indicate that Phelipanche aegyptiaca and S. hermonthica have retained functional genes involved in strigolactone biosynthesis, suggesting that the parasites use both endogenous and exogenous strigolactones and have mechanisms to differentiate the two.
基金supported by the USDA-ARS through CRIS project 6606-21220-014–00Dthe National Institute of Food and Agriculture–Specialty Crops Research Initiative grant 2016-51181-25408“Coordinated development of genetic tools for pecan”。
文摘A collection representing the native range of pecan was planted at the US DA-ARS Southeastern Fruit and Tree Nut Research Station,Byron,GA.The collection(867 trees)is a valuable genetic resource for characterizing important horticultural traits.Canopy density during leaf fall is important as the seasonal canopy dynamics provides insights to environmental cues and breeding potential of germplasm.The ability of visual raters to estimate canopy density on a subset of the provenance collection(76 trees)as an indicator of leaf shed during autumn along with image analysis values was explored.Mean canopy density using the image analysis software was less compared to visual estimates(11.9%vs 18.4%,respectively).At higher canopy densities,the raters overestimated foliage density,but overall agreement between raters and measured values was good(ρc=0.849 to 0.915),and inter-rater reliability was high(R^(2)=0.910 to 0.953).The provenance from Missouri(MOL),the northernmost provenance,had the lowest canopy density in November,and results show that the higher the latitude of the provenance,the lower the canopy density.Based on regression,the source provenance latitude explained 0.609 of the variation using image analysis,and0.551 to 0.640 when based on the rater estimates of canopy density.Visual assessment of pecan canopy density due to late season leaf fall for comparing pecan genotypes provides accurate and reliable estimates and could be used in future studies of the whole provenance collection.
文摘Rice production in Pakistan is constraint by many factors pertaining to prevalent planting techniques. A research on the feasibility of new planting techniques （direct seeding on flat, transplanting on flat, direct seeding on ridges, transplanting on ridges and parachute planting） in transplanted and direct wet-seeded rice was undertaken at Dera Ismail Khan region of Pakistan＇s North West Frontier Province during 2002 and 2003. Among the planting techniques, the best performance for the yield formation and economic evaluation was noted for transplanting on flat during both years. Chinese parachute planting technology also showed very promising results in most of the parameters. Direct seeding on ridges could not excel transplanting on flat and parachute planting during both cropping seasons. The findings concluded the feasibility of parachute planting technology along with traditional rice transplanting on flat over all other planting techniques being practiced in the area.
文摘Chemical control is presently the most cost-effective means to control kudzu;however, some of the herbicides labeled for kudzu control have substantial non-target toxicity, poor selectivity, high cost, long soil persistence, high soil mobility and/or high use rates. The present study evaluated other herbicides for efficacy in suppressing aboveground kudzu biomass in replicated field trials at three sites over two years. A single application of aminopyralid, triclopyr or metsulfuron resulted in at least 90% kudzu suppression in the following season at two locations. After a second year of treatment those herbicides and fluroxypyr produced at least 90% kudzu suppression, and 100% kudzu control was reached on some test plots. Glyphosate, glufosinate and mesotrione were less effective in controlling kudzu. Given the rapid growth potential of kudzu, complete eradication should be pursued. None of the herbicides evaluated in the present study could reliably achieve eradication of mature kudzu with two applications, so additional control efforts would be required.
基金supported by grants from the National Natural Science Foundation of China (no.32272564 and no.32302387)the National Key R&D Program of China (no.2023YFD1401100 and no.2021YFD1700101)+3 种基金the Science and Technology Innovation Program of Hunan Province (no.2022RC1017)Hunan Outstanding Youth Fund Project (no.2023JJ10025)the Training Program for Excellent Young Innovators of Changsha (kq2106079)the Hunan Agricultural Science and Technology Innovation Fund Project (2022CX01 and 2023CX02).
文摘Weeds pose a significant threat to crop production,resulting in substantial yield reduction.In addition,they possess robust weedy traits that enable them to survive in extreme environments and evade human con-trol.In recent years,the application of multi-omics biotechnologies has helped to reveal the molecular mechanisms underlying these weedy traits.In this review,we systematically describe diverse applications of multi-omics platforms for characterizing key aspects of weed biology,including the origins of weed spe-cies,weed classification,and the underlying genetic and molecular bases of important weedy traits such as crop–weed interactions,adaptability to different environments,photoperiodicflowering responses,and herbicide resistance.In addition,we discuss limitations to the application of multi-omics techniques in weed science,particularly compared with their extensive use in model plants and crops.In this regard,we provide a forward-looking perspective on the future application of multi-omics technologies to weed science research.These powerful tools hold great promise for comprehensively and efficiently unraveling the intricate molecular genetic mechanisms that underlie weedy traits.The resulting advances will facilitate the development of sustainable and highly effective weed management strategies,promoting greener practices in agriculture.
