The excessive nitrogen （N） fertilizer input coupled with flood irrigation might result in higher N leaching and lower nitrogen recovery efficiency （NRE）. Under an intensive rice system in the Ningxia irrigation re...The excessive nitrogen （N） fertilizer input coupled with flood irrigation might result in higher N leaching and lower nitrogen recovery efficiency （NRE）. Under an intensive rice system in the Ningxia irrigation region, China, environmental friendly N management practices are hreavily needed to balance the amount of N input for optimum crop production while minimize the nitrogen loss. The objective of this study was to determine the influences of side-dressing （SD） technique in mechanical transplanting systems on the NRE, N leaching losses and rice yield in anthropogenic-alluvial soil during two rice growing seasons （2010-2011）. Four fertilizer N treatments were established, including conventional urea rate （CU, 300 kg ha-1 yr-1）; higher SD of controlled-release N fertilizer rate （SD1,176 kg ha-1 yr-1）; lower SD of controlled-release N fertilizer rate （SD2, 125 kg ha-1 yr-1）; and control （CK, no N fertilizer）. Field lysimeters were used to quantify drainage from undisturbed soil during six rice growing stages. Meanwhile, the temporal variations of total nitrigen （TN）, NO3--N, and NH4＋-N concentrations in percolation water were examined. The results showed that SD1 substantially improved NRE and reduced N leaching losses while maintaining rice yields. Across two years, the averaged NRE under SD1 treatment increased by 25.5% as relative to CU, but yet the rice yield was similar between two treatments. On average, the nitrogen loss defined as TN, NH4＋-N, and NO3--N under the SD1 treatment reduced by 27.4, 37.2 and 24.1%, respectively, when compared with CU during the study periods. Although the SD2 treatment could further reduce N leaching loss to some extent, this technique would sharply decline rice yield, with the magnitude of as high as 21.0% relative to CU treatment. Additionally, the average NRE under SD2 was 11.2% lower than that under SD1 treatment. Overall, the present study concluded that the SO technique is an effective strategy to reduce N leaching and increase NRE, thus potentially mitigate local environmental threat. We propose SD1 as a novel alternative fertilizer technique under an irrigated rice-based system in Ningxia irrigation region when higher yields are under consideration.展开更多
It is essential to develop innovative approaches that can apply N more efficiently. The objective of this study was to examine in-season side-dress urea and ammonium nitrate (UAN) applications to cotton on no-till soi...It is essential to develop innovative approaches that can apply N more efficiently. The objective of this study was to examine in-season side-dress urea and ammonium nitrate (UAN) applications to cotton on no-till soils with high residual N fertility. A field trial was conducted near Milan, TN in 2011 and 2012 with strip plots in a RCB design with three replicates. The following six in-season side-dress fluid UAN treatments were compared: 1) zero N;2) low uniform-rate N application of 56 kg·N·haǃ3) high uniform-rate N application of 78.4 kg·N·haǃ4) ordinary variable-rate N application algorithm for each sub plot based on the average Normalized Difference Vegetation Index (NDVI) value in that sub plot;5) reversed variable-rate N application algorithm for each sub plot based on average NDVI of that sub plot;and 6) N application rate based on the average NDVI value in each strip plot. All plots received 26 kg·N·haǃ as diammonium phosphate before cotton planting each year. Leaf N concentrations were mostly enhanced with all side-dress N applications ranging from 56 to 78 kg·N·haǃ relative to zero N during early to late bloom although this upland field had high initial soil N fertility and received pre-plant application of 26 kg·N·haǃ across the treatments each year. However, NDVI, plant height, and lint yield were rarely improved with side-dress N application. The three variable-rate N application algorithms consumed 7.8 to 12.3 kg·haǃ more N than the low uniform-rate application of 56 kg·N·haǃ, but 10.1 to 14.6 kg·haǃ less N than the high uniform rate of 78.4 kg·N·haǃ. Our results indicate that the current N recommendations for cotton in Tennessee may be too high on upland soils with high initial N fertility.展开更多
基金supported by the National Science and Technology Major Project of China (2014ZX07201009)the Special Foundation for Basic Scientific Research of Central Public Welfare Institute of China (BSRF201306)the Sustainable Agricultural Technique Research and Development Project Phase II between China and Japan
文摘The excessive nitrogen （N） fertilizer input coupled with flood irrigation might result in higher N leaching and lower nitrogen recovery efficiency （NRE）. Under an intensive rice system in the Ningxia irrigation region, China, environmental friendly N management practices are hreavily needed to balance the amount of N input for optimum crop production while minimize the nitrogen loss. The objective of this study was to determine the influences of side-dressing （SD） technique in mechanical transplanting systems on the NRE, N leaching losses and rice yield in anthropogenic-alluvial soil during two rice growing seasons （2010-2011）. Four fertilizer N treatments were established, including conventional urea rate （CU, 300 kg ha-1 yr-1）; higher SD of controlled-release N fertilizer rate （SD1,176 kg ha-1 yr-1）; lower SD of controlled-release N fertilizer rate （SD2, 125 kg ha-1 yr-1）; and control （CK, no N fertilizer）. Field lysimeters were used to quantify drainage from undisturbed soil during six rice growing stages. Meanwhile, the temporal variations of total nitrigen （TN）, NO3--N, and NH4＋-N concentrations in percolation water were examined. The results showed that SD1 substantially improved NRE and reduced N leaching losses while maintaining rice yields. Across two years, the averaged NRE under SD1 treatment increased by 25.5% as relative to CU, but yet the rice yield was similar between two treatments. On average, the nitrogen loss defined as TN, NH4＋-N, and NO3--N under the SD1 treatment reduced by 27.4, 37.2 and 24.1%, respectively, when compared with CU during the study periods. Although the SD2 treatment could further reduce N leaching loss to some extent, this technique would sharply decline rice yield, with the magnitude of as high as 21.0% relative to CU treatment. Additionally, the average NRE under SD2 was 11.2% lower than that under SD1 treatment. Overall, the present study concluded that the SO technique is an effective strategy to reduce N leaching and increase NRE, thus potentially mitigate local environmental threat. We propose SD1 as a novel alternative fertilizer technique under an irrigated rice-based system in Ningxia irrigation region when higher yields are under consideration.
文摘It is essential to develop innovative approaches that can apply N more efficiently. The objective of this study was to examine in-season side-dress urea and ammonium nitrate (UAN) applications to cotton on no-till soils with high residual N fertility. A field trial was conducted near Milan, TN in 2011 and 2012 with strip plots in a RCB design with three replicates. The following six in-season side-dress fluid UAN treatments were compared: 1) zero N;2) low uniform-rate N application of 56 kg·N·haǃ3) high uniform-rate N application of 78.4 kg·N·haǃ4) ordinary variable-rate N application algorithm for each sub plot based on the average Normalized Difference Vegetation Index (NDVI) value in that sub plot;5) reversed variable-rate N application algorithm for each sub plot based on average NDVI of that sub plot;and 6) N application rate based on the average NDVI value in each strip plot. All plots received 26 kg·N·haǃ as diammonium phosphate before cotton planting each year. Leaf N concentrations were mostly enhanced with all side-dress N applications ranging from 56 to 78 kg·N·haǃ relative to zero N during early to late bloom although this upland field had high initial soil N fertility and received pre-plant application of 26 kg·N·haǃ across the treatments each year. However, NDVI, plant height, and lint yield were rarely improved with side-dress N application. The three variable-rate N application algorithms consumed 7.8 to 12.3 kg·haǃ more N than the low uniform-rate application of 56 kg·N·haǃ, but 10.1 to 14.6 kg·haǃ less N than the high uniform rate of 78.4 kg·N·haǃ. Our results indicate that the current N recommendations for cotton in Tennessee may be too high on upland soils with high initial N fertility.
