设施土壤有机氮组分及番茄产量对水氮调控的响应

【目的】酸解铵态氮和酸解氨基酸氮是土壤有机氮的主要组分,可表征土壤的供氮能力,并在氮素矿化、固定、迁移以及为植物生长供氮过程中起到至关重要的作用。研究水、氮调控下设施土壤有机氮组分和番茄产量的相互关系,为评价设施土壤肥力变化和制定科学合理的水、氮管理措施提供科学依据。【方法】田间定位试验在沈阳农业大学的温室内进行了5年,供试作物为番茄,栽培垄上覆盖薄膜,打孔移栽番茄幼苗,膜下滴灌。定位试验三个氮肥处理为施N75、300、525kg/hm^2,记为N1、N2和N3;三个灌水量为25、35和45kPa灌水下限(灌水始点土壤水吸力),记为W1、W2和W3,共9个肥水处理组合。在试验第五年番茄生长期(2016年4—8月)调查了番茄产量及其构成,在休闲期(2016年9月)测定0—10、10—20和20—30cm土层土壤有机氮组分、有机碳和全氮含量。【结果】9个处理中,土壤全氮、有机碳和除酸解氨基糖氮外的有机氮组分含量均随土层深度的增加而降低,且0—10、10—20和20—30cm土层间含量差异显著(P<0.05)。三个土层中酸解总氮占土壤全氮的66.0%、64.6%和55.2%,是土壤有机氮的主要存在形态。土壤酸解总氮中各组分含量及其所占比例的大小顺序为酸解氨基酸氮、酸解铵态氮>酸解未知态氮>酸解氨基糖氮。灌水下限和施氮量对番茄产量及单果重的影响均达极显著水平(P<0.01),水氮交互效应也达显著水平(P<0.05)。休闲期土壤酸解铵态氮与番茄产量间显著负相关(P<0.05)。番茄产量W1N2(25kPa+N300kg/hm^2)、W2N1(35kPa+N75kg/hm^2)和W1N1(25kPa+75kg/hm^2)处理间差异不显著。【结论】灌水和施氮量及其交互效应对各土层土壤全氮、酸解总氮、酸解铵态氮和酸解氨基酸氮的影响均达到极显著水平(P<0.01),而对土壤有机碳的影响不显著(P>0.05)。相同施氮量下,0—30cm土层酸解铵态氮和0—20cm土层酸解氨基酸氮含量均在土壤水吸力维持在35~6kPa范围内达最高值,此土壤水分含量下的0—20cm土层酸解氨基酸氮含量在施N75kg/hm^2时达到最大值。从节水减氮和番茄产量的角度考虑,控制土壤水吸力不低于35kPa、每季随水施N75kg/hm^2为供试番茄生产条件下最佳的水、氮组合量。

Response of soil organic nitrogen fractions and tomato yield to irrigation and nitrogen fertilization in greenhouse

【Objectives】Acidolysable ammonium N (AN) and acidolysable amino acid N (AAN) are the dominated forms of soil organic nitrogen, which play key roles in the processes of soil nitrogen metabolism and nitrogen supply for plant growth. The effect of long-term irrigation and nitrogen fertilization on the AN and AAN contents was investigated, to evaluate soil nitrogen supply ability and provide reference for scientific water and nutrient management in greenhouse.【Methods】A five-year’s tomato field experiment was conducted in the greenhouse of Shenyang Agricultural University. The field was mulched with plastic film and drip irrigation pipes were loaded under the film. The treatment included three nitrogen rates of 75 kg/hm2 (N₁), 300 kg/hm2 (N₂) and 525 kg/hm2 (N₃), and three irrigation rate, in which the irrigation amounts were controlled in soil water tension ranges of 25–6 kPa (W₁), 35–6 kPa (W₂) and 45–6 kPa (W₃). The yield and yield components of tomato were investigated in August 2016. The contents of soil organic nitrogen fractions, total nitrogen (TN) and organic carbon (SOC) in 0–10 cm, 10–20 cm and 20–30 cm soil depths were determined in the fallow period (September, 2016).【Results】The proportions of acidolysable N (AHN) in 0–10, 10–20 and 20–30 cm deep of soil were 66.0%, 64.6% and 55.2%, respectively. The contents of TN, SOC and all soil organic nitrogen fractions, except acidolysable amino sugar N (ASN), decreased with the increasing of soil depths, and the differences of contents among the three soil depths were significant at 5% level. The content and the proportion of each fraction in the AHN was in order of AAN, AN > acidolysable unknown N (UN) > ASN. Under the same N application rate, the contents of AN in 0–30 cm soil depths and the contents of AAN in 0–20 cm soil depths were both the highest in the irrigation treatment of W₂. Moreover, the contents of AAN in 0–10 and 10–20 cm soil depths were also the highest in the W₂N₁ treatment (35 kPa + 75 kg/hm2). The single effect of irrigation and nitrogen rate on tomato yield and yield components were extremely significant (P < 0.01), and their interaction was also significant (P < 0.05). AN content during the fallow period had a significant negative correlation with tomato yield. There were no significant differences in tomato yield among the treatments of W₁N₂ (25 kPa + 300 kg/hm2), W₂N₁ (35 kPa + 75 kg/hm2) and W₁N₁ (25 kPa + 75 kg/hm2).【Conclusions】Irrigation and nitrogen fertilization significantly influence the contents of total nitrogen, acidolysable nitrogen, acidolysable amino acid nitrogen and acidolysable ammonium nitrogen in the soil (P < 0.01), but not on soil organic carbon contents. Significant interaction of irrigation and fertilization is existed at the same time. In the view of water-saving and nitrogen-reducing with high tomato yield, keeping soil water suction in range of 35–6 kPa, and applying N of 75 kg/hm2 is the optimum combination of irrigation and nitrogen fertilization in tomato production inside greenhouse.