聚丙烯酰胺对坡地苹果园水土流失和土壤养分流失的影响

为了改善坡地苹果园的土壤环境,遏制水土流失和土壤养分流失,探寻聚丙烯酰胺适宜的干撒施用量,2010—2012年在陕北丘陵沟壑区的坡地苹果园,以不施聚丙烯酰胺为对照,分别撒施0.6、0.8、1.0、1.2、1.4和1.6 g·m^-2的聚丙烯酰胺,监测果园地表产流、土壤流失、养分流失和苹果植株生长状况.结果表明: 坡地果园的径流量和5—7月的产流次数均随聚丙烯酰胺撒施量的增加呈“V”型变化,其中撒施量为1.0 g·m^-2时最低,但果园侵蚀泥沙量则随聚丙烯酰胺撒施量的增加而降低.地表径流和侵蚀泥沙中的铵态氮、速效磷和速效钾的浓度均随聚丙烯酰胺撒施量的增加而降低;聚丙烯酰胺可显著降低地表径流中的硝态氮含量,对侵蚀泥沙中的硝态氮含量则无显著影响;侵蚀泥沙中的有机质、全氮、全磷和全钾含量均随聚丙烯酰胺撒施量的增加而降低.聚丙烯酰胺提高了苹果单果质量及产量,但对苹果植株生长及果实风味品质无显著影响.聚丙烯酰胺在坡地苹果园中的适宜撒施量应为1.0 g·m^-2.

Effects of polyacrylamide on soil erosion and soil nutrient loss in sloped apple orchards.

In order to improve the soil environment, reduce soil erosion and soil nutrient loss, and explore the suitable dry broadcasting rate of polyacrylamide (PAM) in sloped apple orchard, experiments of different dry broadcasting rates of polyacrylamide were carried out in apple orchards with a slope of 20° in the hilly-gully region of northern Shaanxi from 2010 to 2012. PAM treatment levels included 0, 0.6, 0.8, 1.0, 1.2, 1.4 and 1.6 g·m^-2. Surface runoff, eroded sediment, soil nutrient loss, and the growth of apple trees were monitored. Results showed that the surface runoff and runoff yield times from May to July exhibited a “V” shape with the increase of PAM application rate, and reached a minimum at the 1.0 g·m^-2 level. However, the sediment yield decreased with increasing the PAM application rate. The concentrations of the ammonium nitrogen, available phosphorus, and available potassium in surface runoff and sediment decreased with increa-sing the PAM application rate. PAM significantly reduced the content of nitrate nitrogen in surface runoff, whereas it had no significant effect on nitrate nitrogen in sediment. Organic matter, total nitrogen, total phosphorus, and total potassium in the sediment decreased with increasing the PAM application rate. Moreover, PAM improved average fruit mass and fruit yields in sloped orchards, but it had no significant effect on the growth of apple trees and apple fruit flavor. An application le-vel of PAM at 1.0 g·m^-2 should be suitable in sloped apple orchards.