滴灌氮肥用量对设施菜地硝态氮含量及环境质量的影响

【目的】滴灌施肥较传统施肥更为精准的将肥水输送至作物的根区,减少肥料的用量,降低土壤水分和养分深层渗漏带来的环境风险。本试验研究滴灌管理下不同氮肥(N)用量对设施菜地供氮能力及环境质量的影响,以期获得滴灌水肥一体化管理条件下最佳施氮用量。【方法】采用日光温室冬春茬黄瓜-秋冬茬番茄轮作,共设计4个化肥氮用量梯度(N_0、N_1、N_2、N_3,对应冬春茬黄瓜季施氮0、300、600、900 kg/hm~2;秋冬茬番茄季施氮0、225、450、675 kg/hm2)3年定位研究比较不同氮用量下0-100 cm土体硝态氮、电导率(EC_(5:1))、pH动态变化计算了各施氮水平下设施蔬菜生产的氮素表观平衡、氮肥利用率和经济效益。【结果】随着种植年限的延长,N_2和N_3处理0-100 cm土体硝态氮和盐分积累显著土壤硝态氮含量分别由2008年黄瓜季季平均14.4~31.1和14.9~41.0 mg/kg增至2010年番茄季季均76.4~119.8和129.0~184.5 mg/kg,分别增加了1.9~5.1和3.5~7.7倍;两处理EC。分别由2008年黄瓜季季平均379.6~514.3和407.0~476.7S/cm增至2010年番茄季季平均663.0~1212.4和710.0~1359.6μS/cm分别增加了0.3~1.8和0.5~2.0倍。与N_2和N_3处理相比,N_1处理节氮50%~66.7%,经过三年的种植0-100cm土层季均硝态氮含量和EC_(5:1)分别下降了35.5%~67.4%和6.0%~25.2%,pH增加0.06~0.18,氮肥利用率显著增加9.0~13.8个百分点而种植蔬菜的经济效益未有显著下降。【结论】温室滴灌冬春茬黄瓜一秋冬茬番茄经济施氮量分别为N 300和225kg/hm~2,既能保证3年5季蔬菜根层(0-60 cm)土层硝态氮处于相对适宜水平,具有较好的经济和环境效益。

Nitrate nitrogen contents and quality of greenhouse soil applied with different N rates under drip irrigation

【Objectives】 Drip irrigation could effectively inhibit nutrient leakage as water and nutrients can be accurately sent to close the crop root zone. In this paper, the soil mineral N contents and environmental qualities were detected under different N rates and drip irrigation, to provide a base for efficient N management in vegetable production. 【Methods】 A three-years' feild experiment was conducted with winter-spring cucumber and autumn-winter tomato double cropping system in a greenhouse. Four N rates were applied as 0, 300, 600, 900 kg/hm2 for cucumber and 0, 225, 450, 675 kg/hm2 for tomato under drip irrigation (correspondingly recorded as N0, N1, N2, N3). The mineral nitrogen contents, salinity (EC5∶1) and acidity (pH) of 0-100 cm soil depth were investigated, and the economic and environmental efficiencies of N were calculated.【Results】 As the elongation of the cropping year, the NO3--N contents under N2 and N3 treatments in 0-100 cm soil profile were significantly increased from 14.4-31.1 and 14.9-41.0 mg/kg in cucumber season in 2008, respectively, to 76.4-119.8 and 129.0-184.5 mg/kg in tomato season in 2010, respectively, increased by 0.3-1.8 and 0.5-2.0 times respectively. The electrical conductivity (EC5∶1) of 0-100 cm soil profile under N2 and N3 was significantly increased from 379.6-514.3 and 407.0-476.7 S/cm, respectively, to 663.0-1212.4 and 710.0-1359.6 S/cm of tomato season in 2010, respectively, increased by 0.3-1.8 and 0.5-2.0 times. The N rates in N1 was 33.3%-50% of N2 and N3. Compared with N2 and N3, the NO3--N content and EC5∶1 of N1 decreased by 35.5%-67.4% and 6.0%-25.2% after three years cultivation, and the pH and NUE increased by 0.06-0.18 unit and 9.0-13.8 percentage points.【Conclusions】 Under this condition, the proper N rate for winter-spring cucumber and autumn-winter tomato was recommend as N 300 and 225 kg/hm2. In most crop seasons (5 seasons), the NO3--N contents in 0-60 cm depth were in the proper range for cucumber and tomato growth, and no significant accumulation of NO3--N was observed below 60 cm in the soil under this recommended N rate.