等高固氮植物篱模式对坡耕地土壤养分的影响

Studies on soil nutrient redistribution under contour hedgerow system.

对坡耕地土壤剖面养分的研究结果表明,等高固N植物篱模式对养分的影响表现在对养分的归还和在土壤剖面的再分配。培植植物篱5年后,该系统中与植物篱不同距离位点0～40cm土层土壤有机质和全N含量分别比对照高1.2～2.3倍和0.5～1.7倍,有效磷和速效钾显著增加,表明植物篱可有效改善土壤养分状况。研究结果还表明在植物篱模式下0～60cm土层土壤有机质和全N含量均比种植带相应土层高,0～20cm土层有效磷和有效钾含量明显比种植带各位点相应土层高,表明植物篱与农作物之间无养分竞争;种植带下部0～40cm土层养分状况比种植带中部和上部相应土层优越,种植带上部各土层养分状况最差;植物篱内40cm以下土层中有效磷和速效钾含量比种植带下相同土层低,说明植物篱根系可将土壤深层的P、K吸收并通过刈割枝叶返还种植带,发挥养分泵的功能。因此,植物篱通过生物固N和养分泵的功能提高种植带上层土壤养分含量和促进矿质养分循环。

Contour hedgerow system has been regarded as the most favorable agroforestry systems for water and soil conservation. However, it is more concerned whether hedgerows in the system compete with crops for belowground resources, especially nutrient beyond their crown areas. The nutrients in soil profiles in the system were analyzed for determining nutrients competition between hedgerows and crops in the system and nutrients redistribution pattern in the system. Organic matter and total nitrogen contents of topsoil (0~40cm) at different positions in hedgerow system are increased 1.2 - 2.3 times and 0.5 - 1.7 times over those of control respectively, and available P and exchangeable K have also increased remarkably after five years of hedgerow establishment, suggesting that contour hedgerow system is very effective for topsoil nutrient improvement. In hedgerow system, soil nutrients of 0~20 cm beneath hedgerow are higher than those beneath alley, therefore competition for nutrient doesn' t occur between hedgerow and crops. The results also show that nutrients status in alley varies with positions, namely, nutrients in downside alley are better than those in the middle and upper alley, and upper alley is the poorest position in alley. Available P and exchangeable K below 40 cm beneath hedgerow was lower than those beneath alley, suggesting that root system of hedgerow is functioned as 'nutrient pump' to uptake K and P from deep soil beyond crop root system and return them to topsoil by pruning of hedgerow.