设施大棚黄瓜–紫甘蓝轮作体系产量和土壤氮平衡对氮素调控剂的响应

  【目的】  研究脲酶抑制剂和硝化抑制剂对设施大棚蔬菜产量、土壤氮分布及土壤–蔬菜系统氮平衡的影响，为调控优化设施蔬菜生产中的氮素养分管理技术、减少氮素损失提供科学依据。  【方法】  供试蔬菜大棚位于河北省涿州市，种植年限8年，种植模式为黄瓜 (Cucumis sativus L.)–紫甘蓝 (Brassica oleracea L.) 轮作。试验设不施氮肥处理 (N₀) 和施氮肥处理；在相同施氮量下，再设施氮不施抑制剂 (N)、配施脲酶抑制剂 (N+UI)、配施硝化抑制剂 (N+NI) 和配施脲酶抑制剂+硝化抑制剂 (N+UI+NI) 4个处理。所有处理在黄瓜定植之前基施有机肥41500 kg/hm2，除N₀外，其他处理同时底施化肥N 56.3 kg/hm2。在试验开始一个月后每隔10～15天进行一次追肥，全生育期总计共施入化肥N 304 kg/hm2。紫甘蓝茬不再施用有机肥，只在定植前底施化肥N 135 kg/hm2 (N₀处理除外)。测定指标包括黄瓜、紫甘蓝产量和不同生育时期土壤硝态氮含量和收获季植株含氮量，分析作物吸氮量、氮素利用效率、土壤无机氮累积量和土壤-蔬菜系统的氮素平衡状况。  【结果】  与N处理相比，N₀处理黄瓜产量没有显著降低，但紫甘蓝产量显著下降了12.7 %；3个配施抑制剂处理 (N+UI、N+NI和N+UI+NI) 的黄瓜产量较N处理无显著增加，但吸氮量显著提高了7.6%～11.9%，氮素表观利用率、氮肥农学效率和氮素收获指数分别显著提高34.5%～53.3%，13.5～22.5倍和1.5～3.6个百分点，其中N+UI+NI处理的农学效率和收获指数最高；3个配施抑制剂处理的紫甘蓝产量显著高于N处理，其中N+UI+NI又显著高于N+UI和N+NI，3个抑制剂处理紫甘蓝吸氮量和氮肥农学效率分别显著提高18.0%～21.4%和34.8%～68.3%。3个抑制剂处理的两茬累积氮素表观利用率和农学效率均显著高于N处理，分别显著提高了76.9%~94.2%和52.8%~98.3%，其中N+NI的累积表观氮素利用率最高，N+UI+NI农学效率最高。综合产量和氮素利用效率考虑，N+UI+NI的效果最优。配施抑制剂后，黄瓜、紫甘蓝各生育时期耕层土壤硝态氮含量显著提高，至紫甘蓝收获期，0—100 cm剖面的硝态氮累积量显著增加215.1%～275.2%，氮素盈余量显著下降15.1%～17.8%，但其氮素盈余率仍维持在35.5%～37.1%。  【结论】  由于连续的高氮投入，导致种植多年的蔬菜大棚土壤氮素供应水平较高，当季施用氮肥以及配施氮抑制剂的增产效应不明显。但在适宜的氮素肥力水平下，氮肥配施脲酶/硝化抑制剂可显著提高蔬菜产量和氮素利用效率，增加经济效益，同时显著降低土壤氮素盈余率，并将氮素有效保存在100 cm以内的土层中。然而，菜田土壤累积的大量氮素在大水漫灌时可能发生淋溶损失，因此在多年连作的土壤肥力水平较高的设施蔬菜生产中，氮肥的优化施用与调控技术仍值得进一步研究。

Response of vegetable yields and soil nitrogen balance to nitrogen regulators in a greenhouse cucumber-purple cabbage rotation system

  【Objectives】  In this study, we analyzed the effects of urease and nitrification inhibitors on vegetable yield, soil N distribution, and soil-vegetable N balance in a greenhouse facility. The aim was to provide a scientific basis for optimizing N nutrient management techniques and reducing N loss in the facility farmland.  【Methods】  In Zhuozhou, Hebei Province, a field controlled experiment of cucumber-purple cabbage rotation was conducted in a greenhouse for 8 years using no N input as the control (N₀). The treatments were no inhibitor (N), plus application of urease inhibitor (N+UI), plus application of nitrification inhibitor (N+NI), N and combined application of urease + nitrification inhibitor (N+UI+NI). All treatments were applied with the same quantity of P and K fertilizer. In cucumber season, organic fertilizer (41500 kg/hm2) and chemical fertilizer N (56.3 kg/hm2) were applied as a basal fertilizer, and N 304 kg/hm2 in toal was applied since 30 days after planting in frequency of every 10–15 days. In purple cabbage season, only N 135 kg/hm2 was used as a basal fertilizer before transplanting. We investigated the differences in vegetable yield, economic benefits, soil N distribution, nitrate leaching characteristics, and soil-vegetable N balance among the treatments.  【Results】  Compared with N treatment, the cucumber yield in N₀ did not decrease significantly; however, the yield of purple cabbage decreased by 12.7%. The cucumber yield of N+UI, N+NI and N+UI+NI treatments did not increase significantly, but the N uptake significantly increased by 7.6% to 11.9% compared with N treatment. The apparent N utilization efficiency, agronomic efficiency and harvest index of nitrogen fertilizer significantly increased by 34.5%–53.3%, 13.5–22.5 times, and 1.5–3.6 percentage points, respectively. N+UI+NI treatment had the hightest agronomic efficiency and harvest index. The purple cabbage yield of N+UI, N+NI and UI+NI were significantly higher than that of N treatment, and the yield of N+UI+NI was markedly higher than those of N+UI and N+NI. N uptake and agronomic efficiency of purple cabbage were significantly increased by 18.0%–21.4% and 34.8%–68.3%, respectively. The accumulated N use efficiency and agronomy efficiency of cucumber-purple cabbage were significantly increased by 76.9%–94.2% and 52.8%–98.3%. In addition, the application of urease/nitrification inhibitors could substantially increase NO₃–-N content in 0–20 cm depth during the growing period of cucumber-purple cabbage. At harvest, the 0–100 cm soil layer in purple cabbage recorded a 215.1%–275.2% increase in NO₃-N content, 15.1%–17.8% decrease in N surplus amount, and the N surplus rate remained at 35.5%–37.1%.  【Conclusions】  In greenhouse, vegetables are planted for many years with continuous N input, leading to high soil N supply. The use of N fertilizer and combined application of N inhibitors do not improve vegetable yield, N utilization efficiency, and economic benefits. Under optimal N supply, the combined application of N fertilizer with urease/nitrification inhibitors could increase vegetable yield, N utilization efficiency, and economic benefits and effectively retain N in the 0–100 cm soil layer. Consequently, the N surplus rate is considerably reduced. However, the large quantity of N accumulated in vegetable field soil may still be leached and lost through flooding. Therefore, further studies are needed on N fertilizer optimization and regulation techniques to produce greenhouse vegetables under high soil fertility levels in a continuous cropping system.