种植苜蓿对黄绵土表土理化性质的影响

The effects of lucerne on top soil properties of Huangmian soil

对定西黄绵土多年苜蓿地与传统耕地的表层土壤理化性质进行了比较研究。结果表明,长期种植苜蓿促进了土壤有机质、全氮在土壤表层的累积,减少了土壤表层有效硫的损耗,但对土壤有机质、全氮累积的影响作用主要表现在0～10cm土层内,而且土壤有机质和土壤全氮含量之间存在显著的正相关关系;耕地中的速效氮主要以NO3--N为主,而苜蓿地中NH4+-N和NO3--N的含量差异不明显。长期种植苜蓿对土壤表层全磷、全钾、速效钾和速效磷的影响甚微。苜蓿地表层土壤的坚实度显著高于耕地。苜蓿根系的穿插有利于打破由于长期耕作造成的犁底层,而对整个土体的土壤容重影响不大。

The top soil properties of Huangmian soil under lucerne grown for many years were compared with those of soil under conventional tillage in Dingxi. In lucerne fields (LF), soil organic matter (SOM) and total nitrogen (TN) accumulation was accelerated in the top soil, but mainly at 0~10 cm depth. Also, available sulphur (AS) loss was reduced in the top soil. Moreover, between the organic matter and TN in the soil there existed a marked positive mutual relationship. The main component of available nitrogen in the top soil of conventionally tilled fields (CTF) was nitrate, but in LF, the contents of ammonium and nitrate in the top soil were not significantly different. The influence of longterm lucerne growing on the top soil total phosphorus (TP), total potassium (TK), available phosphorus (AP) and available potassium (AK) was very slight. At 0~10 cm depth, the soil density of LF was markedly higher than that of CTF. Lucerne's root system was very good at breaking the ploughing pan created by many years of tillage, but the influence on soil bulk density of the whole soil profile (about 0~300 cm) was small.