Aims Crop nitrogen(N)and phosphorus(P)stoichiometry can influence food nutritive quality and many ecosystem processes.However,how and why N and P stoichiometry respond to long-term agricul-tural management practices(e...Aims Crop nitrogen(N)and phosphorus(P)stoichiometry can influence food nutritive quality and many ecosystem processes.However,how and why N and P stoichiometry respond to long-term agricul-tural management practices(e.g.N fertilization and film mulching)are not clearly understood.Methods We collected maize tissues(leaf,stem,root and seed)and soil sam-ples from a temperate cropland under 30-year continuous N fer-tilization and plastic film mulching treatments,measured their C,N and P concentrations(the proportion(%)relative to the sample mass),and used structural equation models to uncover the re-sponding mechanisms for crop N and P contents(the total amount(g/m2)in crop biomass).Important Findings Long-term N fertilization increased N concentrations in all crop tissues but sharply decreased P concentrations in vegetative tis-sues(leaf,stem and root),thereby reducing their C/N ratio and increasing C/P and N/P ratios.The drop in P concentration in vegetative tissues was due to the dilution effect by biomass in-crement and the priority of P supply for seed production.In con-trast,film mulching decreased N concentration but increased P concentrations in most crop tissues,thereby increasing C/N ratio and reducing C/P and N/P ratios.Film mulching increased crop P content by increasing soil temperature and moisture;whereas,mulching showed little effect on crop N content,because a posi-tive effects of soil temperature may have canceled out a negative effect by soil moisture.This indicated a decoupling of P and N uptake by crops under film mulching.In conclusion,N fertiliza-tion and plastic film mulching showed opposite effects of on crop N and P stoichiometry.展开更多
基金This work was supported by the National Science Foundation of China(41601307,41771328,41601247 and 41701330)the National Key Research and Development Program of China(2016YFD0200304).
文摘Aims Crop nitrogen(N)and phosphorus(P)stoichiometry can influence food nutritive quality and many ecosystem processes.However,how and why N and P stoichiometry respond to long-term agricul-tural management practices(e.g.N fertilization and film mulching)are not clearly understood.Methods We collected maize tissues(leaf,stem,root and seed)and soil sam-ples from a temperate cropland under 30-year continuous N fer-tilization and plastic film mulching treatments,measured their C,N and P concentrations(the proportion(%)relative to the sample mass),and used structural equation models to uncover the re-sponding mechanisms for crop N and P contents(the total amount(g/m2)in crop biomass).Important Findings Long-term N fertilization increased N concentrations in all crop tissues but sharply decreased P concentrations in vegetative tis-sues(leaf,stem and root),thereby reducing their C/N ratio and increasing C/P and N/P ratios.The drop in P concentration in vegetative tissues was due to the dilution effect by biomass in-crement and the priority of P supply for seed production.In con-trast,film mulching decreased N concentration but increased P concentrations in most crop tissues,thereby increasing C/N ratio and reducing C/P and N/P ratios.Film mulching increased crop P content by increasing soil temperature and moisture;whereas,mulching showed little effect on crop N content,because a posi-tive effects of soil temperature may have canceled out a negative effect by soil moisture.This indicated a decoupling of P and N uptake by crops under film mulching.In conclusion,N fertiliza-tion and plastic film mulching showed opposite effects of on crop N and P stoichiometry.
