早播及耕作措施对黄土高原半干旱区春小麦土壤氮磷元素的影响

Effects of early sowing and tillage measures on nitrogen and phosphorus in the soil supporting spring wheat in the semi-arid area of the Loess Plateau

为探讨早播及耕作措施对农田生态系统土壤氮磷元素影响规律,对黄土高原半干旱区早播、正常播下不同耕作措施[传统耕作(T)、传统耕作+秸秆还田(TS)、免耕(NT)、免耕+秸秆覆盖(NTS)]春小麦(Triticum aestivum)生育期0~40 cm土壤进行分析,以正常播种传统耕作春小麦为对照,研究早播及耕作措施对春小麦土壤氮磷元素的影响。结果表明:(1)不同处理下春小麦土壤N素(TN、NO3^(-)-N、NH4^(+)-N)、P素(TP)含量均具有表聚性特征,其土壤N∶P均值(1.713)低于全国平均值(5.2),同时其变异水平系数处于26.99%~77.28%,属中等变异水平;(2)全生育期0~40 cm土层,早播春小麦土壤TN、NH4^(+)-N含量及N∶P均值显著低于正常播23.1%~32.5%,不利于土壤TN、NH4^(+)-N含量积累,而NO3^(-)-N含量及NO3^(-)-N∶N均值显著高于正常播30.5%、41.5%,有助于土壤NO3^(-)-N含量的固存,同时早播处理下土壤TP含量整体高于正常播处理;(3)秸秆覆盖措施(NTS、TS)下土壤TN、TP含量高于NT、T,但速效氮(NO3^(-)-N、NH4^(+)-N)养分含量表现相反;(4)不同处理下春小麦土壤TP含量在生育期间趋于稳定,而N素含量在分蘖期及开花期变化较显著。因此,选择适宜播种时间及耕作管理措施有助于提高该区作物土壤N、P元素的积累转化效率,加快发展黄土高原半干旱区农田生态系统恢复进程。

To study the effects of early sowing and tillage measures on soil nitrogen and phosphorus in a farmland ecosystem,0-40 cm of soil supporting spring wheat(Triticum aestivum)in the semi-arid region of the Loess Plateau was collected and analyzed.Under early sowing and normal sowing conditions,the different tillage measures were as follows:traditional tillage(T),traditional tillage+straw returning(TS),no tillage(NT),and no tillage+straw mulching(NTS).Results were as follows.(1)Under different treatments,the contents of N(TN,NO3^(-)-N,and NH4^(+)-N)and P(TP)in spring wheat-related soil had the characteristics of surface aggregation.The average value of soil N:P(1.713)was lower than the national average value(5.2)and the coefficient of variation was 26.99%-77.28%,which belonged to the medium variation level.(2)In the 0-40 cm soil layer,the TN,NH4^(+)-N,and N:P levels of early sowing spring wheat were significantly lower than the levels found with normal sowing(i.e.,by 23.1%-32.5%),which was not conducive to the accumulation of TN and NH4^(+)-N,whereas NO3^(-)-N and NO3^(-)-N:N levels were significantly higher in early sowing spring wheat than the levels achieved with normal sowing(i.e.,by 30.5%and 41.5%,respectively),which was conducive to the retention of NO3^(-)-N in the soil.(3)The contents of TN and TP under straw mulching conditions(NTS and TS)were higher than those under NT and T,but the contents of available nitrogen(NO3^(-)-N and NH4^(+)-N)showed the opposite trend.(4)Under different treatments,the contents of TP in the soil tended to be stable during the growth period,whereas the contents of N changed significantly at the tillering and flowering stages.Therefore,selecting suitable sowing times and tillage management measures will help to improve the accumulation and transformation efficiency of N and P elements in crop soil and will accelerate the restoration process of farmland ecosystems in the semi-arid area of the Loess Plateau.