不同栽培模式及施氮量对土壤团聚体的影响

通过长期定位试验研究了不同栽培模式(休闲,常规,覆草,垄沟覆盖)和施氮量(N0,N120,N240)条件下西北旱地土壤团聚体组成、稳定性及其与土壤有机碳、土壤水分、产量等的相关关系,结果表明:干筛法0.25~10mm团聚体含量垄沟覆盖显著低于常规和覆草栽培模式,而>10mm的大团聚体显著高于常规和覆草模式,垄沟覆盖栽培促进0.5~5 mm团聚体向更大级别进一步团聚;干筛法0.25~10mm团聚体总量N240处理显著高于N0。湿筛法>0.25 mm水稳性团聚体含量覆草和垄沟覆盖栽培显著高于常规,不同施氮量间无显著差异。干筛法团聚体平均重量直径(MWD)和几何平均直径(GMD)垄沟覆盖显著大于覆草和常规模式;水稳性团聚体MWD覆草模式显著大于常规,覆草模式GMD显著大于垄沟覆盖模式;不同施氮量下水稳性团聚体MWD差异不显著,N0处理的GMD显著大于N120、N240。覆盖栽培可以提高土壤团聚体的稳定性,不同施氮量间团聚体稳定性差异不显著。历年2m土层土壤贮水量平均值与水稳性团聚体GMD呈显著正相关,不同栽培模式主要通过影响土壤水分来影响土壤团聚体状况;历年平均产量与水稳性团聚体GMD呈显著负相关,说明干旱半干旱地区土壤水稳性团聚体直径应较小,利于提高土壤保水和水分有效性,进而促进作物产量的提高。

Effects of different cultivating patterns and nitrogen fertilizer application on soil aggregates

The composition, distribution and stability of aggregate, and its relationships with soil organie carbon, soil moisture and yield were studied in a long-term fixed-location experiment. Different cultivating patters(F,CC,SC,RF+SC)and different nitrogen fertilizer amount(N0,N120,N240)were tested to investigate their effects on soil aggre-gates in dryland of northwest China.The results showed that:ridge furrow+straw mulching pattem(RF+SC)planting significantly reduced the 0.25~10 mm dry-sieving aggregate content while significantly increased aggregate that is bigger than 10 mm, in comparison with conventional and straw mulching(SC) patterns. RF+SC pattern planting also promoted formation of bigger size aggregate from 0.5~5 mm one. Content of 0.25~10 mm aggregate by dry-sieving method was significantly higher in N240 treatment than in NO treatment. Compared to conventional pattemn, straw mulching signifi-cantly increased content of water stable aggregate with diameters greater than 0.25 mm.There were no significant differences in water stable aggregate with diameters greater than 0.25 mm among the different nitrogen fertilization treatments. Mean weight diameter(MWD)and geometric mean diameter(GMD)of soil aggregate by dry-sieving method were signifi- cantly higher in RF+SC pattem than in SC and conventional patterns. MWD of water-stable aggregate in SC pattern was significantly greater than in conventional patterns, and its GMD was also significantly greater than in RF+SC pattem. NO treatment significantly improved GMD of water stable aggregate than N120 and N240 treatment; however, there was no significant difference in MWD among the three different N fertilizer treatments. Straw mulching and RF+SC patterns improved soil aggregate stability. There was no significan difference in aggregate stability among different nitrogen treatments. A significant positive correlation was observed between the average of water storage in 2 m soil profile over the 7 years and GMD of water stable aggregate, indicating that diffferent planting patterns affect soil aggregation through its in fluence on soil water and that soil water condition is the determent factor affected soil water stable aggregatte in the region. The correlation between average yield and GMD of water stability aggregate was significantly negative, indicating that small aggregate is benefit for crop yield.