优化施氮对设施番茄土壤硝态氮残留及土壤氮平衡的影响

Effects of optimal nitrogen fertilization on N balance and nitrate-N accumulation in greenhouse tomato fields

【目的】设施蔬菜生产中普遍存在氮肥施用过量、有机无机肥配合不合理以及灌水频繁等问题,我们通过田间试验研究了优化施氮模式对番茄产量、土壤硝态氮残留和氮平衡的影响,为蔬菜生产优质高效和减量优化施肥提供科学依据。【方法】试验在山东惠民蔬菜大棚内进行,灌水量为农户平均灌水量(482.5 mm)的80%(390 mm),供试蔬菜为番茄,覆膜栽培。试验在基施猪粪N 65 kg/hm^(2)条件下,设传统施氮量(N 1000 kg/hm^(2),TF)和3个减氮量50%处理:鸡粪处理(OF)、普通尿素处理(CF)、包膜尿素处理(CRF)。于移栽前和收获后采集0—180 cm土壤样品。每次施肥前,取0—90 cm深(每30 cm为一层)土壤样品,测定硝态氮和铵态氮含量。番茄收获后,取植株和果实样品,测定生物量和养分含量。【结果】施氮处理之间番茄产量和地上部吸氮量没有显著差异。传统施氮量处理(TF),尽管施用2倍于优化处理的施氮量,但番茄产量没有明显提高。OF、CF和CRF 3个减氮处理0—60 cm土壤硝态氮残留量分别为N 190.1、227.2、310.5 kg/hm^(2),分别比TF处理降低56.61%、43.35%和22.59%;表观氮素损失量分别为N 416.6、443.7和352.3 kg/hm^(2),分别比TF处理降低45.72%、42.20%和54.10%;土壤氮素平衡盈余率也分别比TF处理降低34.26%、33.40%和61.78%(P<0.05)。在同等施氮量下,包膜尿素能够使氮素更多地保持在土壤上层,CRF处理0—30 cm土层硝态氮累积量比CF处理平均高43.0%。生育期内,在移栽后20~60和110~120天有两个明显表层硝态氮积聚过程,在移栽后80~100天,30—60 cm土层有一硝态氮消耗过程。【结论】供试条件下,施氮量减少一半能有效降低设施番茄土壤硝态氮残留及淋失风险,不会造成产量的下降。施用包膜尿素比单施有机肥或普通尿素更有利于降低氮素的淋洗损失和实现产量与环境效益双赢。

【Objectives】Excessive nitrogen fertilizer application,the unreasonable mixing ratio of organic and inorganic fertilizers,and frequent irrigation are common in facility vegetable production.Here,we proposed three N application modes and studied their effects on tomato yield,soil N residue,and N balance.The results will provide a scientific basis for efficient tomato production and optimized N fertilization.【Methods】The experiment was carried out in a vegetable greenhouse in Huimin,Shandong Province.We irrigated the greenhouse at 80%(390 mm)of the average irrigation(482.5 mm)in the study area.Tomato was cultivated with film mulching.Using the basal application of pig manure at N 65 kg/hm^(2),the conventional nitrogen application rate(N 1000 kg/hm^(2),TF)and three treatments with 50%nitrogen reduction were set:chicken manure treatment(OF),ordinary urea treatment(CF)and coated urea treatment(CRF).Soil samples were collected at 0-180 cm depth before transplanting and after harvest.Before each fertilization,soil samples were collected to a depth of 0-90 cm(at 30 cm interval)to determine nitrate and ammonium nitrogen contents.After tomato harvest,plant and fruit samples were collected to determine biomass and nutrient content.【Results】There were no significant differences in tomato yield and N uptake among the treatments.However,the N rate was one fold higher in TF than in CF treatment.CF,OF and CRF treatments maintain appropriate soil N supply levels during the growing period.Correspondingly,the residual NO3--N amount in 0-60 cm soil layer of CF,OF,and CRF treatments were 190.1,227.2 and 310.5 kg/hm^(2).These values were 56.61%,43.35%,and 22.59%lower than those recorded in TF treatment.The apparent N loss in CF,OF,and CRF treatment were 416.6,443.7,and 352.3 kg/hm^(2),45.72%,42.20%and 54.10%lower than those in TF treatment,respectively.Compared with TF,soil N balance surplus in CF,OF,and CRF(P<0.05)decreased by 34.26%,33.40%,and 61.78%,respectively.Coated urea maintained more N in the upper soil layer than the other treatments,and its NO_(3)^(-)-N accumulation in 0-30 cm soil layer was 43.0%higher than that in CF treatment.We found two obvious accumulation processes of NO_(3)^(-)-N in the soil surface layer during the growing period of tomato.The first was during the 20-60 days period,and the second occurred during the 110-120 day period after transplanting.Further,there was a depletion process in the 30-60 cm soil layer during the 80-100 day period.【Conclusions】Under the experimental conditions,reducing half of the conventional N application rate for tomato can effectively reduce the NO3--N residue and leaching in the soil of greenhouse tomato,and will not cause a decrease in yield.The application of coated urea is more beneficial to reduce the leaching of N than poultry manure or ordinary urea,and more beneficial to achieve a win-win situation of yield and environmental benefits.