不同杂草盖度夏播紫花苜蓿人工草地N、P生态化学计量特征

通过测定并分析不同杂草盖度紫花苜蓿田苜蓿叶、茎以及0~30 cm土壤中N、P含量及其氮磷比,研究了不同杂草盖度对苜蓿、杂草和土壤N、P生态化学计量特征的影响.结果表明:紫花苜蓿人工草地自第二茬时出现较多杂草,对照组的土壤全N含量较高;杂草中度侵害等级的土壤全P含量较高;对照组和杂草轻度侵害等级的土壤氮磷比较高.苜蓿叶和茎的N、P含量及氮磷比均受杂草盖度的影响,且第二茬和第三茬的苜蓿叶氮磷比小于14,说明苜蓿的生长受氮限制,可在其刈割后追施氮肥.在同一杂草侵害等级下,第三茬苜蓿叶和茎的N、P含量均高于第一茬和第二茬.在不同杂草侵害等级和不同茬次下,相同杂草的N、P含量及氮磷比也不相同;苜蓿叶、茎和土壤中N、P含量以及氮磷比均能影响相应杂草的N、P生态化学计量特征,并发现特定的变化趋势.

The ecological stoichiometry of N and P in summer-seeded alfalfa grassland of different weed coverage

Through the measurement and analysis of N, P and N:P of the alfalfa leaf, stem and 0~30 cm of soil, the study inquired a relation of N, P contents and N:P between afalfa, weed and soil in different weed coverage of alfalfa grassland.The results showed that, there were more weeds in alfalfa field since the second cut.The soil N content of contrast group was higher than other in alfalfa grassland;The soil P content was higher than other in alfalfa field with medium level of weed invasion;The soil N:P was higher in contrast group and slight level of weed invasion;The N, P contents and N:P of alfalfa leaf and stem were influenced by weed coverage.The N:P of alfalfa leaf were less than 14 at the second or third cut so that the growth of alfalfa was limited by N element.Then, N fertilizer was applied since alfalfa cutting.Under same level of weed invasion, the N and P contents of third cut of alfalfa leaf and stem were higher than the first and second cuts of them.The same weed had different N, P contents and N:P in different level of weed invasion and different cut;The N and P stoichiometry characteristic of weed was affected by N, P contents and N:P of alfalfa and soil.Then, no specific trend was found.