夏季休闲是黄土高原旱地小麦常见的蓄纳雨水、恢复地力的措施。随着氮肥用量的增加,一季小麦收获后,旱地土壤剖面累积的硝态氮量不断增加,休闲期间降雨量高,残留硝态氮的去向是值得研究的问题。利用^(15)N标记法研究小麦收获后残留肥料...夏季休闲是黄土高原旱地小麦常见的蓄纳雨水、恢复地力的措施。随着氮肥用量的增加,一季小麦收获后,旱地土壤剖面累积的硝态氮量不断增加,休闲期间降雨量高,残留硝态氮的去向是值得研究的问题。利用^(15)N标记法研究小麦收获后残留肥料氮在黄土高原旱地(陕西长武)夏季休闲期间的去向,即小麦收获后在微区土壤表层(0~15 cm)施入^(15)N标记的硝态氮肥(30 kg hm^(-2)(以纯氮计),约相当于当地小麦一季作物收获后土壤残留肥料氮量),休闲结束后,采集0~200 cm土壤样品,测定了土壤全氮、硝态氮含量及其^(15)N丰度。结果表明,小麦收获(即休闲开始)时0~200 cm土壤剖面硝态氮累积量在205~268 kg hm-2之间(平均244 kg hm^(-2)),累积量较高。夏季休闲期间降水量为157 mm,属欠水年,但休闲结束后,^(15)N标记肥料氮向下迁移已达80 cm土层,下移深度在45~65cm之间,说明,旱地休闲期间硝态氮的淋溶作用不可忽视。夏季休闲结束后,加入的^(15)N标记肥料氮平均损失率为28%,损失机理值得进一步研究。展开更多
Pot experimeats were carried out to estimate N2 fixation by vetch, milk vetch, sickle alfalfa and broadbean in pure stand using a 15N-labelled soil. Winter wheat was used as the non-fixing control. The 15N-labelled so...Pot experimeats were carried out to estimate N2 fixation by vetch, milk vetch, sickle alfalfa and broadbean in pure stand using a 15N-labelled soil. Winter wheat was used as the non-fixing control. The 15N-labelled soil used was prepared by growing corn-wheat-corn successively on a nearly organic-matter-free Xiashu loess supplemented with adequate amounts of (15NH4)aSO4, P, K and micronutrients, then incorporating these 15N-labelled plant msterials into the soil after each harvest, and allowing the plant materials to be decomposed aerobically for 410 d after incorporation of the plant material of the third crop. The 15N enrichment of wheat plant-N varied slightly with organs,with a maximum difference of 9.8%. Based on 15N enrichment of soil N inferred from the mean value of the 15N enrichment in different organs of wheat 79%-91% of total N in the tops and 67%-74% of total N in the roots of legumes studied were derived from atmosphere. Estimate by isotope dilution method was in good agreement with that by the conventional difference method provided values obtained by the latter were corrected for seed N, and also with that from the measurement of N accumulated in the tops of the legumes.展开更多
文摘夏季休闲是黄土高原旱地小麦常见的蓄纳雨水、恢复地力的措施。随着氮肥用量的增加,一季小麦收获后,旱地土壤剖面累积的硝态氮量不断增加,休闲期间降雨量高,残留硝态氮的去向是值得研究的问题。利用^(15)N标记法研究小麦收获后残留肥料氮在黄土高原旱地(陕西长武)夏季休闲期间的去向,即小麦收获后在微区土壤表层(0~15 cm)施入^(15)N标记的硝态氮肥(30 kg hm^(-2)(以纯氮计),约相当于当地小麦一季作物收获后土壤残留肥料氮量),休闲结束后,采集0~200 cm土壤样品,测定了土壤全氮、硝态氮含量及其^(15)N丰度。结果表明,小麦收获(即休闲开始)时0~200 cm土壤剖面硝态氮累积量在205~268 kg hm-2之间(平均244 kg hm^(-2)),累积量较高。夏季休闲期间降水量为157 mm,属欠水年,但休闲结束后,^(15)N标记肥料氮向下迁移已达80 cm土层,下移深度在45~65cm之间,说明,旱地休闲期间硝态氮的淋溶作用不可忽视。夏季休闲结束后,加入的^(15)N标记肥料氮平均损失率为28%,损失机理值得进一步研究。
文摘Pot experimeats were carried out to estimate N2 fixation by vetch, milk vetch, sickle alfalfa and broadbean in pure stand using a 15N-labelled soil. Winter wheat was used as the non-fixing control. The 15N-labelled soil used was prepared by growing corn-wheat-corn successively on a nearly organic-matter-free Xiashu loess supplemented with adequate amounts of (15NH4)aSO4, P, K and micronutrients, then incorporating these 15N-labelled plant msterials into the soil after each harvest, and allowing the plant materials to be decomposed aerobically for 410 d after incorporation of the plant material of the third crop. The 15N enrichment of wheat plant-N varied slightly with organs,with a maximum difference of 9.8%. Based on 15N enrichment of soil N inferred from the mean value of the 15N enrichment in different organs of wheat 79%-91% of total N in the tops and 67%-74% of total N in the roots of legumes studied were derived from atmosphere. Estimate by isotope dilution method was in good agreement with that by the conventional difference method provided values obtained by the latter were corrected for seed N, and also with that from the measurement of N accumulated in the tops of the legumes.
