| Based on the problem that China is short in potash resource and transgenic anti-inset cotton is susceptible to low potassium nutrition,in order to study the influence of straw returning to field(taking the place of chemical potassium fertilization)on cottonseed lipid content and its physiological and ecological mechanism,field experiment was carried out in 2012-2013 in the research station of Jiangsu Agricultural Academy in Nanjing.The study focused on:(1)Effects of straw incorporation substitute for potassium fertilization on cottonseed yield under wheat-cotton double cropping system on soils of varied fertility;(2)The potential analysis of straw-returning taking the place of chemical potassium application in the wheat-cotton rotation system by study the oil accumulation in cottonseed;(3)The potential analysis of straw-returning taking the place of chemical potassium application in the wheat-cotton rotation system by study the carbon-nitrogen metabolism in cottonseed.The main results were as follows:1.According to the difference of straw type,year and site,straw incorporation could replace chemical potassium in varying degrees.Straw incorporation could increase cottonseed yield under the condition of optimized nitrogen and phosphate fertilization level.Boll no.was an most important factors of yield components in both sites.Effects of wheat straw incorporation(WSI)and cotton straw incorporation(CSI)were not consistent between years due to difference of soil available K content.In Nanjing,K fertilizer rate of substitution(KRS)of WSI of 4500 kg ha-1 were all greater than or approximately equal to 100%without CSI in 2012.In 2013,KRS of WSI of 4500-9000 kg ha-1 were 36.5%-87.8%without CSI,and 6.3%-32.0%increased KRS with CSI of 9000 kg ha-1.In Dafeng,there were no significant differences among all straw incorporation treatments,which mean no need to application of K-fertilizer or straw in 2012.In 2013,WSI of 4500 kg ha-1 could completely replace the K-fertilizer except for W1C1(71.7%).2.The potassium content in the cottonseed at 17th d,24th d is a key nutrition factor that may lead to the difference of cottonseed oil content.The phosphatidic acid phosphatase(PPase)plays an more important role than glucose 6-phosphate dehydrogenase(G6PDH),enol phosphate type pyruvate carboxylase(PEPc)in cottonseed oil accumulation in response to soil potassium nutrition.Under the condition of optimized nitrogen(300 kg N ha-1)and phosphate(150 kg P2O5 ha-1)fertilization level,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,but soil K content was significantly different.The 17th d,24th day after the anthesis(DAA)of the flower was the key period for the difference of the content of cottonseed oil formation.Under the chemical potassium fertilization and the straw returning condition,the phosphatidic acid phosphatase(PPase)contribute more to cottonseed oil accumulation than glucose 6-phosphate dehydrogenase(G6PDH),enol phosphate type pyruvate carboxylase(PEPc)in response to soil potassium nutrition.3.From the perspective of carbon supply and compete,straw returning stimulated early sucrose input and increased the activity of SuSy and invertase,while decreased the content of protein.Under the short-term straw returning and the chemical potassium fertilizer condition,soluble sugar content and sucrose content increased significantly in the 17th day after the anthesis(DAA)of flower.Sucrose transformation rate(STR)and soluble sugar transformation rate(SSTR)also increased significantly during the period of fertility.In addition to sucrose phosphate synthase(SPS),the average activity of sucrose synthase(SuSy)and invertase(acidic,alkaline)activity were significantly positively correlated with STR and SSTR.Straw returning and potassium application all reduced cottonseed protein content during development,while increased the highest activity of GS/GOGAT.The absolute value of potassium stress coefficient of the oil was greater than protein. |
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