Northern Guinea Savanna of Nigeria soils are continuously and intensively cultivated, resulting in soil quality degradation, carbon stock depletion, accelerated soil erosion and soil nutrient depletion. Effects of lan...Northern Guinea Savanna of Nigeria soils are continuously and intensively cultivated, resulting in soil quality degradation, carbon stock depletion, accelerated soil erosion and soil nutrient depletion. Effects of land use change on soil carbon stocks (SOC) are of concern regarding greenhouse gas emissions mitigation and sustainable crop production, because there is a need for food sufficiency while conserving the environment. Also, managing soils under intensive use and restoring degraded soils are top priorities for a sustained agronomic production while conserving soil and water resources. Hence, this study;“Tillage, Desmodium intortum, fertilizer rates for carbon stock, soil quality and grain yield in Northern Guinea Savanna” is aimed at devising possible mitigating measures for soil quality degradation, carbon stock depletion and impoverished crop yields using Zea mays as test crop. The study was a Randomized Complete Block Design (RCBD) in split-split plot arrangement with four replicates. The four main tillage and Desmodium intortum combination treatments were: 1) Maize −without Desmodium + Conventional tillage (MC), 2) Maize + Desmodium live-mulch incorporated and relayed + Conservation tillage (MDIC), 3) Maize + Desmodium in no-tillage system (MDNT), 4) Maize + Desmodium in strip tillage (MDST). The main treatment plots were each divided to accommodate four (4) rates of N (60, 80, 100 and 120 kg·ha−1) as sub plots, while the N rate plots were further divided to accommodate three (3) rates of P (6.6, 13.2, and 26.4 kg·ha−1) as sub-subplots. Findings support that Desmodium intercrops with Maize treatments (MDIC, MDNT, and MDST) resulted in increased organic carbon contents in 2013, with MDNT resulting in significantly higher organic carbon content (7.37 g·kg−1 in 2012 and 8.37 g·kg−1 in 2013) than the other treatments. Also, zero tillage practice (MDNT) sequestered significantly higher carbon stock (18.06 t C ha−1), followed by minimum tillage (MDIC) that sequestered 15.99 t C ha−1 than the other treatments. Highest grain yield of 2.61 tha−1 under MDIC and MDNT was followed by MDST and least under MC. Total score of soil quality assessment gave least score values of 13 under MDIC and MDNT;thus best soil quality (SQ1) was ascribed to the minimum tillage with D. intortum intercrop and relayed (MDIC) and Zero tillage with D. intortum (MDNT) treatments. Maize Strip cropped with D. intortum treatment (MDST) was ranked SQ2.展开更多
China's capital market has been developing continuously in recent years, and the scale of capital market is getting larger and larger. The participation structure of China's stock market is not dominated by in...China's capital market has been developing continuously in recent years, and the scale of capital market is getting larger and larger. The participation structure of China's stock market is not dominated by institutions as in European and American stock markets. A large number of investors in China participate in the buying and selling of stocks, which results in the current situation of high turnover rate of Chinese stocks. Based on Fama-French's three-factor model and the idea of quantitative investment, this paper takes turnover rate as momentum factor, dynamic price-earnings ratio as growth factor, and corporate price-to-book ratio as quality factor, and uses the sectional data of 2021 to analyze the stock price returns of more than 4,000 listed companies (including GEM, etc.) in China.展开更多
本文将研究贝叶斯法则视角下的空间自相关误差自相关模型(Spatial Autoregressive Model with Autoregressive Disturbances,SARAR模型)变量选择问题。通过将基于BIC准则的子集选择法推广到空间模型,实现SARAR模型的变量选择,并证明在...本文将研究贝叶斯法则视角下的空间自相关误差自相关模型(Spatial Autoregressive Model with Autoregressive Disturbances,SARAR模型)变量选择问题。通过将基于BIC准则的子集选择法推广到空间模型,实现SARAR模型的变量选择,并证明在一定条件下,对于SARAR模型的变量选择BIC准则具有良好的渐近性质。同时本文还将利用Monte Carlo模拟验证BIC准则能够很好的实现SARAR模型的变量选择。最后以股票收益率为例,在验证股票收益率具有空间效应的前提下,利用BIC准则对影响股票收益率的众多财务指标进行变量选择。展开更多
文摘Northern Guinea Savanna of Nigeria soils are continuously and intensively cultivated, resulting in soil quality degradation, carbon stock depletion, accelerated soil erosion and soil nutrient depletion. Effects of land use change on soil carbon stocks (SOC) are of concern regarding greenhouse gas emissions mitigation and sustainable crop production, because there is a need for food sufficiency while conserving the environment. Also, managing soils under intensive use and restoring degraded soils are top priorities for a sustained agronomic production while conserving soil and water resources. Hence, this study;“Tillage, Desmodium intortum, fertilizer rates for carbon stock, soil quality and grain yield in Northern Guinea Savanna” is aimed at devising possible mitigating measures for soil quality degradation, carbon stock depletion and impoverished crop yields using Zea mays as test crop. The study was a Randomized Complete Block Design (RCBD) in split-split plot arrangement with four replicates. The four main tillage and Desmodium intortum combination treatments were: 1) Maize −without Desmodium + Conventional tillage (MC), 2) Maize + Desmodium live-mulch incorporated and relayed + Conservation tillage (MDIC), 3) Maize + Desmodium in no-tillage system (MDNT), 4) Maize + Desmodium in strip tillage (MDST). The main treatment plots were each divided to accommodate four (4) rates of N (60, 80, 100 and 120 kg·ha−1) as sub plots, while the N rate plots were further divided to accommodate three (3) rates of P (6.6, 13.2, and 26.4 kg·ha−1) as sub-subplots. Findings support that Desmodium intercrops with Maize treatments (MDIC, MDNT, and MDST) resulted in increased organic carbon contents in 2013, with MDNT resulting in significantly higher organic carbon content (7.37 g·kg−1 in 2012 and 8.37 g·kg−1 in 2013) than the other treatments. Also, zero tillage practice (MDNT) sequestered significantly higher carbon stock (18.06 t C ha−1), followed by minimum tillage (MDIC) that sequestered 15.99 t C ha−1 than the other treatments. Highest grain yield of 2.61 tha−1 under MDIC and MDNT was followed by MDST and least under MC. Total score of soil quality assessment gave least score values of 13 under MDIC and MDNT;thus best soil quality (SQ1) was ascribed to the minimum tillage with D. intortum intercrop and relayed (MDIC) and Zero tillage with D. intortum (MDNT) treatments. Maize Strip cropped with D. intortum treatment (MDST) was ranked SQ2.
文摘China's capital market has been developing continuously in recent years, and the scale of capital market is getting larger and larger. The participation structure of China's stock market is not dominated by institutions as in European and American stock markets. A large number of investors in China participate in the buying and selling of stocks, which results in the current situation of high turnover rate of Chinese stocks. Based on Fama-French's three-factor model and the idea of quantitative investment, this paper takes turnover rate as momentum factor, dynamic price-earnings ratio as growth factor, and corporate price-to-book ratio as quality factor, and uses the sectional data of 2021 to analyze the stock price returns of more than 4,000 listed companies (including GEM, etc.) in China.
文摘本文将研究贝叶斯法则视角下的空间自相关误差自相关模型(Spatial Autoregressive Model with Autoregressive Disturbances,SARAR模型)变量选择问题。通过将基于BIC准则的子集选择法推广到空间模型,实现SARAR模型的变量选择,并证明在一定条件下,对于SARAR模型的变量选择BIC准则具有良好的渐近性质。同时本文还将利用Monte Carlo模拟验证BIC准则能够很好的实现SARAR模型的变量选择。最后以股票收益率为例,在验证股票收益率具有空间效应的前提下,利用BIC准则对影响股票收益率的众多财务指标进行变量选择。
