减氮配施缓释氮肥对棉田土壤酶活性和氮素吸收利用的影响

为探明减氮配施缓释氮肥对棉田土壤酶活性和氮素吸收利用的影响,通过试验研究减氮、配施不同比例缓释氮肥对棉花土壤理化性质、酶活性、无机氮含量、氮肥利用率及棉花产量的影响。试验选用新陆早64号棉花品种,设置2种施氮方式,分别为常规全施尿素(T2)和缓释氮肥与尿素不同比例配施(US),配施处理按照施氮量设3个水平,分别为不减氮U_0.8S_0.2(T3)、U_0.6S_0.4(T4),减氮20% U_0.6S_0.2(T5)、U_0.4S_0.4(T6),减氮40% U_0.4S_0.2(T7)、U_0.2S_0.4(T8),不施氮肥(T1)为对照,共8个处理。对棉花不同生育期内土壤的理化性质、酶活性、无机氮含量及成熟期棉花氮素含量和产量进行测定与分析,并计算氮肥利用率。结果表明:与常规全施尿素相比,配施缓释氮肥能显著提高土壤含水量和全氮含量,其中,以缓释氮肥与尿素4∶6配施(T4)处理的土壤含水量最大,较常规全施尿素(T2)在棉花苗期、蕾期、花期、铃期和吐絮期分别提高了14.07%,11.05%,7.58%,6.22%,6.65%;T4处理的土壤全氮在花期显著高于常规全施尿素(T2)处理,达到1.24 g/kg。减氮20%配施缓释氮肥(T5、T6)处理各生育时期的土壤脲酶活性、蔗糖酶活性、过氧化氢酶活性、碱性磷酸酶活性和铵硝态氮含量与常规全施尿素(T2)间无显著差异,减氮20%配施缓释氮肥(T5、T6)处理成熟期土壤脲酶活性与硝态氮含量较不减氮T4处理分别减少了28.20%,26.40%和11.13%,8.32%。此外,减氮20%(T5、T6)处理的氮肥利用率显著高于常规全施尿素(T2)处理,分别为62.09%和62.43%,产量及其构成因素与常规全施尿素(T2)间无显著差异。综上,减氮20%配施缓释氮肥(T5、T6)处理与常规全施尿素(T2)处理相比土壤酶活性、无机氮含量及产量差异不显著,氮肥利用率显著高于T2处理,可以确保棉花全生育期的氮素供给,避免[JP]氮素的大量浪费,达到棉花高产及氮肥高效利用的目的。

Effects of Nitrogen Reduction Combined with Slow Release Nitrogen Fertilizer on Soil Enzyme Activity and Nitrogen Uptake in Cotton Field

In order to explore the effects of nitrogen reduction combined with slow release nitrogen fertilizer on soil enzyme activity and nitrogen absorption and utilization in cotton field, the effects of nitrogen reduction and different proportions of slow release nitrogen fertilizer on soil physical and chemical properties, enzyme activity, inorganic nitrogen content, nitrogen use efficiency and cotton yield were studied. The cotton variety Xinluzao 64 was used in the experiment. Two nitrogen application methods were set up:The conventional total urea (T2) and slow release nitrogen fertilizer combined with urea (US). The combined application treatments were set at three levels according to the nitrogen application rate, namely, no nitrogen reduction, U_0.8S_0.2 (T3) and U_0.6S_0.4 (T4) (the subscript values refer to the proportion of urea and slow release fertilier in the total nitrogen); nitrogen reduction of 20%, U_0.6S_0.2 (T5) and U_0.4S_0.4 (T6); nitrogen reduction of 40%, U_0.4S_0.2 (T7) and U_0.2S_0.4 (T8); and no nitrogen application (T1) as the control, with a total of eight treatments. The soil physical and chemical properties, enzyme activity, inorganic nitrogen content, nitrogen content and yield of cotton at different growth stages were measured and analyzed, and the nitrogen use efficiency was calculated. The results showed that compared with the conventional total application of urea, the combined application of slow release nitrogen fertilizer could significantly increase the soil water content and total nitrogen content. Among them, the soil water content of T4 was the highest, which was 14.07%, 11.05%, 7.58%, 6.22% and 6.65% higher than that of T2 at the seedling stage, bud stage, flowering stage, boll stage and boll opening stage of cotton, respectively. The soil total nitrogen of T4 was significantly higher than that of T2 at flowering stage, reaching 1.24 g/kg. There was no significant difference in soil urease activity, sucrase activity, catalase activity, alkaline phosphatase activity and ammonium nitrate content between the treatments of T5, T6 and T2 at each growth stage. The soil urease activity and nitrate content in the mature stage of the treatments of T5 and T6 decreased by 28.20%, 26.40% and 11.13%, 8.32%, respectively, compared with the T4. In addition, the nitrogen use efficiencies of T5 and T6 were significantly higher than that of T2, by 62.09% and 62.43%, respectively. But there was no significant difference in yield and its components. In summary, the soil enzyme activity, inorganic nitrogen content and yield of the treatment with 20% nitrogen reduction combined with slow release nitrogen fertilizer (T5, T6) were not significantly different from those of the conventional (T2), and the nitrogen use efficiency was significantly higher, which could ensure the nitrogen supply in the whole growth period of cotton, avoid the nitrogen waste, and achieve the purposes of high yield and efficient utilization of nitrogen fertilizer.