秸秆还田替代化学钾肥对棉麦轮作中棉仁油分累积的效应

为研究棉田化学钾肥的秸秆替代施入对棉仁含油量的影响及其生理生化基础,2012—2013年于江苏省农业科学院试验站进行麦棉两熟周年秸秆还田定位试验,在棉花季设置小麦秸秆不还田(0,W0)、半量还田(4500 kg hm–2,W1)和全量还田(9000 kg hm–2,W2),在小麦季设置棉花秸秆不还田(0,C0)、半量还田(3750 kg hm–2,C1)和全量还田(7500 kg hm–2,C2),两种作物秸秆不同还田量组合后共9个秸秆还田处理,另根据秸秆折合钾肥量,于2012年棉花季开始增设2个钾肥用量处理,即150 kg K2O hm–2和300 kg K2O hm–2(K1和K2)。研究显示,在适宜氮肥(300 kg N hm–2)、磷肥(150 kg P2O5 hm–2)水平下,随着逐年秸秆还田与施钾,土壤速效氮、有效磷年际间差异均不显著,但土壤速效钾含量年际间存在显著差异;花后17 d、24 d是不同处理条件下棉仁含油量差异形成的关键时期;相较于6-磷酸葡萄糖脱氢酶(G6PDH)、磷酸烯醇式丙酮酸羧化酶(PEPC),花后17 d、24 d的磷脂酸磷酸酯酶(PPase)的活性对棉仁油分的通径系数更大。结果表明,短期秸秆还田与单施化学钾肥均主要影响棉田土壤速效钾含量;从棉仁油分累积角度来看,秸秆还田可在很大程度上替代化学钾的施入;花后17 d、24 d棉仁钾含量是影响棉仁含油量的关键因子;秸秆还田替代化学钾肥条件下,PPase较G6PDH、PEPC对棉仁油分的影响更为关键。

Effects of Straw-Returning Instead of Chemical Potassium Application on Oil Accumulation in Cottonseed Embryo in Wheat-Cotton Rotation System

A field experiment was carried out to study the influence of straw returning to field (taking the place of chemical potassium fertilization) on cottonseed lipid content and its physiological mechanism in 2012—2013 in the research station of Jiangsu Agricultural Academy in Nanjing. Application rates of wheat straw were designed as 0, 4500, and 9000 kg ha-1 (W0, W1, and W2) in cotton season. Similarly, application rates of cotton straw were designed as 0, 3750, and 7500 kg ha^-1 (C0, C1, and C2) in wheat reason. There were nine straw-returning treatments with combinations of two kinds of crop straw at returning different amounts. Additionally, according to the straw potassium content, K fertilizer rates were newly designed as 150 and 300 kg K₂O ha^-1 (K1 and K2) in cotton season in 2012. The results showed that under the condition of optimized nitrogen (300 kg N ha^–1) and phosphate (150 kg P₂O₅ ha^–1) fertilization levels, with straw returning and the chemical potassium fertilizer application year by year, the differences of soil available nitrogen and phosphorus between years were not significant, while those of soil K content were significantly different. The 17th day and 24th day after anthesis (DAA) were the key period for the difference of cottonseed oil formation. Under the chemical potassium fertilization and the straw returning condition, the phosphatidic acid phosphatase (PPase) contributed more to cottonseed oil accumulation than glucose 6-phosphate dehydrogenase (G6PDH) and phosphoenolpyruvate carboxylase (PEPC) in response to soil potassium nutrition. The result indicated that, the soil available K content was the major nutrition factor that was significantly affected by the two-years straw returning and the chemical potassium fertilizer application. Straw returning to field can take the place of chemical potassium application to a high extent. The amount of straw returning will affect potassium content of the soil. Low potassium stress will accelerate the aging of cotton plant, and might be a straight reason that caused the difference of oil content. The potassium content in the cottonseed at 17th day, 24th day after anthesis is a key nutrition factor that may lead to the difference of cottonseed oil content. The phosphatidic acid phosphatase (PPase) plays a more important role than glucose 6-phosphate dehydrogenase (G6PDH), phosphoenolpyruvate carboxylase (PEPC) in cottonseed oil accumulation in response to soil potassium nutrition.