Do combined applications of crop residues and inorganic fertilizer lower emission of N2O from soil?

Emissions of N₂O were measured following addition of ¹⁵N‐labelled residues of tropical plant species [Vigna unguiculata (cowpea), Mucuna pruriens and Leucaena leucocephala] to a Ferric Luvisol from Ghana at a rate of 100 mg N/kg soil under controlled environment conditions. Residues were also applied in different ratio combinations with inorganic N fertilizer, at a total rate of 100 mg N/kg soil. N₂O emissions were increased after addition of residues, and further increased with combined (ratio) applications of residues and inorganic N fertilizer. However, ¹⁵N‐N₂O production was low and short‐lived in all treatments, suggesting that most of the measured N₂O‐N was derived from the applied fertilizer or native soil mineral N pools. There was no consistent trend in magnitude of emissions with increasing proportion of inorganic fertilizer in the application. The positive interactive effect between residue‐ and fertilizer‐N sources was most pronounced in the 25:75 Leucaena:fertilizer and cowpea:fertilizer treatments where 1082 and 1130 mg N₂O‐N/g residue were emitted over 30 days. N₂O (log_e) emission from all residue amended treatments was positively correlated with the residue C:N ratio, and negatively correlated with residue polyphenol content, polyphenol:N ratio and (lignin + polyphenol):N ratio, indicating the role of residue chemical composition in regulating emissions even when combined with inorganic fertilizer. The positive interactive effect in our treatments suggests that it is unlikely that combined applications of residues and inorganic fertilizer can lower N₂O emissions unless the residue is of very low quality promoting strong immobilisation of soil mineral N.     

Cover crop effects on nitrogen load in tile drainage from Walnut Creek Iowa using root zone water quality (RZWQ) model

Studies quantifying winter annual cover crop effects on water quality are mostly limited to short-term studies at the plot scale. Long-term studies scaling-up water quality effects of cover crops to the watershed scale provide more integrated spatial responses from the landscape. The objective of this research was to quantify N loads from artificial subsurface drainage (tile drains) in a subbasin of the Walnut Creek, Iowa (Story county) watershed using the hybrid RZWQ-DSSAT model for a maize (Zea mays L.)-soybean [Glycine max (L.) Merr.] and maize-maize-soybean rotations in all phases with and without a winter wheat (Triticum aestivum L.) cover crop during a 25-year period from 1981 to 2005. Simulated cover crop dry matter (DM) and N uptake averaged 1854 and 36 kg ha⁻¹ in the spring in the maize-soybean phase of the 2-year rotation and 1895 and 36 kg ha⁻¹ in the soybean-maize phase during 1981-2005. In the 3-year rotation, cover crop DM and N uptake averaged 2047 and 44 kg ha⁻¹ in the maize-maize-soybean phase, 2039 and 43 kg ha⁻¹ in the soybean-maize-maize phase, and 1963 and 43 kg ha⁻¹ in the maize-soybean-maize phase during the same period. Annual N loads to tile drains averaged 29 kg ha⁻¹ in the maize-soybean phase and 25 kg ha⁻¹ in the soybean-maize phase compared to 21 and 20 kg ha⁻¹ in the same phases with a cover crop. In the 3-year rotation, annual N loads averaged 46, 43, and 45 kg ha⁻¹ in each phase of the rotation without a cover crop and 37, 35, and 35 kg ha⁻¹ with a cover crop. These results indicate using a winter annual cover crop can reduce annual N loads to tile drains 20-28% in the 2-year rotation and 19-22% in the 3-year rotation at the watershed subbasin scale over a 25-year period.     

秸秆厌氧消化预处理技术综述

农作物秸秆是一种重要的富含有机质(80％～90％)的生物质能源,因其复杂的晶体结构,不能直接被厌氧菌群利用来生产沼气.因此以秸秆作为原料发酵时,需要进行预处理,使复杂的晶体结构得到破坏,从而易于被厌氧菌群利用.文章综述了国内外用物理法、化学法、生物法、物化法预处理秸秆的相关研究进展,考查了不同预处理方法对厌氧消化效果的影响.     

基于熵理论和遗传算法的作物灌溉决策的优化研究

为了优化作物灌溉的决策,在综合考虑了灌溉水量、作物水分需求、降雨量、土壤水分含量和作物不同生育阶段缺水对产量的敏感指数等因素的基础上,建立了基于熵理论和遗传算法的优化模型。通过实例试验,结果表明:提出的模型用于作物灌溉决策优化比基本遗传算法计算精度有了明显提高。     

油菜水分胁迫的冠层表面温度特征及诊断研究

对油菜的冠层温度特征进行了研究,并在此基础上建立了油菜的冠气温差模型和CWSI模型。利用建立的CWSI模型对植株含水率进行预测,结果表明:油菜含水率预测值与实测值的平均相对误差小于9.2%;CWSI模型能够实现对油菜含水率的定性和定量分析。     

基于遥感和蚁群算法的多目标种植结构优化

针对农业种植结构与水资源不匹配的问题,以主要作物不同生育期需水特点和区域降水特点吻合性为基础,建立了考虑灌区节水效益、经济效益和生态效益的多目标种植结构优化模型,并以宝鸡峡五泉灌区为例,利用遥感快速获取灌区种植结构信息,并以不同口粮面积约束为条件建立2种优化方案,采用蚁群算法对模型在不同约束下的2种优化方案进行优化求解.结果表明：方案1,2的灌区需水总量为现状的85.4%和83.4%,纯收入比现状在平水年低5.4%和高7.1%,在干旱年低5.9%和高7.3%,降雨耦合度分别在平水年高12.6%和15.6%,干旱年高17.5%和28.6%,对2种不同约束方案优化结果比较得出,方案2为最优调整方案.该研究在未改变原有灌区种植面积的条件下,经种植结构优化调整后,既可保持灌区生态环境的可持续发展,又使灌区经济收入有很大的提高.这对农业节水规划具有较高的实用价值和理论意义.     

基于遗传算法的投影寻踪回归模型在参考作物滕发量预测中的应用

根据朝阳气象站的实测气象数据(降水量、温度、湿度、风速、蒸发量、日照时数),提出基于加速遗传算法的投影寻踪回归模型用于预测朝阳地区参考作物滕发量.用自相关分析技术确定预测因子(气象数据),构造出新的投影指标,采用可变阶的正交Hermite多项式拟合岭函数,并用基于实数编码的加速遗传算法优化投影指标函数,进而构建投影寻踪...     

作物需水量计算模型组件研究与应用

作物需水量的计算在农业用水、水资源与环境评价、作物生长模拟等方面的研究应用有着重要作用,国内外已形成了众多的研究成果与计算方法。通过对目前比较成熟的作物需量计算方法进行收集和筛选,在不同计算模型的特点和适应性分析基础上,对模型进行分类和归集,采用COM技术研究建立了通用性强、应用面广、内容齐全的计算模型组件。模型组件包...     

根系带水质量模型参数灵敏度分析与标定的研究

利用收集的河南省新乡试验站田间试验数据对根系带水质量模型(ROOt Zone Water Quality Model,RZWQM)输入参数进行灵敏度分析和标定.结果表明,通过参数的灵敏度分析结果对RZWQM进行调参,节省参数校核时间,提高精度.参数标定后模拟值与实测值的对比显示,土壤含水量的模拟均方根差和平均相对误差分...     

内蒙古河套灌区主要粮油作物系数的确定

根据FAO-56作物需水量指南推荐的作物系数计算方法,分别计算内蒙古河套灌区磴口试验站小麦、玉米(覆膜与未覆膜)、油料向日葵3种作物的单、双值作物系数。结果表明,磴口试验站单值作物系数较双值作物系数值计算的ET值偏低,双值作物系数计算的ET值与实测结果更为接近,验证了双值作物系数在河套灌区的适用性。