灌水频率和施氮量对番茄生长及水氮淋失的影响

Effects of drip irrigation frequency and nitrogen fertilizer on nitrate leaching and tomato growth

不合理灌溉水氮管理引起的水氮淋失越来越受到关注。本文以日光温室滴灌番茄为对象,研究充分供水条件下水氮管理参数对土壤水氮淋失和番茄生长的影响。试验选取灌水频率和施氮量2个因素,灌水间隔设3、6和9 d 3个水平,施氮量设0、180和300 kg/hm23个水平。在番茄生育期内观测土壤含水率、土壤水势和土壤氮素含量,番茄收获时测定地上部分干物质、产量和氮素吸收量。结果表明,土壤水分深层渗漏和硝态氮淋失几乎发生在番茄整个生育期内,表现出深层渗漏量增大时硝态氮淋失量也增大的同步特征。灌水间隔3 d和6 d处理的生育期累积渗漏量接近,占灌水量的12%,而当灌水间隔增加到9 d时,生育期深层渗漏量明显增加,占灌水量的18%。同一灌水频率下,硝态氮累积淋失量随施氮量的增加呈增加趋势,生育期累积最大水氮淋失量发生在低灌水频率高施氮量处理。灌水频率和施氮量对番茄植株吸氮量和产量的影响未达到统计学上显著水平(P=0.05)。从减少水氮淋失和方便管理两方面考虑,建议温室滴灌番茄适宜的灌水间隔为6 d。

Deep percolation and nitrate leaching caused by unreasonable irrigation and nitrogen management practices are increasingly concerned by designers, managers, and users of irrigation systems. For a drip irrigation system that is properly designed, irrigation frequency is an important management parameter since an improper irrigation frequency may not be able to provide sufficient water for crop growth on time or lead to deep percolation. Field experiments were conducted in a solar heated greenhouse in the growing season of tomato to investigate the effects of drip irrigation frequency and nitrogen applied on deep percolation, nitrate leaching and tomato growth. Three drip irrigation intervals of 3, 6 and 9 d and three nitrogen application levels of 0, 180 and 300 kg/hm^2 were used. The experiments were conducted using a randomized complete block design （RCBD） with three replications and a total of 27 experimental plots were creat- ed. The spatial and temporal distributions of soil water content, soil water potential as well as soil nitrogen content were measured during the growing season of tomato. Fruit yield was recorded individually for each plot. Total dry matter aboveground was measured on harvest and nitrogen uptake was determined by summing of the product of total dry matter aboveground and fruit weight and corresponding nitrogen content. The results indicated that the wetted soil depth was normally less than 30 em as the irrigation interval varied from 3 d to 9 d, increasing with the irrigation interval. Deep percolation and nitrate leaching was observed during the whole growing season of tomato, and the nitrate leaching always increased with the deep percolation. An approximately similar seasonal deep percolation was observed for the irrigation intervals of 3 d and 6 d, accounting for 12 % of the seasonal irrigation amount. However, the seasonal deep percolation, increased greatly as the irrigation interval increased to 9 d, accounting for 18 % of the seasonal irrigation amount. Similarly, nitrate leaching demonstrated a clearly increasing tendency as irrigation interval increased from 6 d to 9 d. For a given irrigation frequency, the seasonal nitrate leaching increased with nitrogen applied. The maximum seasonal nitrate leaching was found in the treatment of the lowest irrigation frequency with highest nitrogen applied （W3N2）. There was no significant influence of drip irrigation frequency and nitrogen applied on plant N uptake and fruit yield of tomato. An irrigation interval of 6 d was recommended for drip irrigated tomato in solar greenhouse when yield, deep percolation, nitrate leaching, and management cost of labor input were considered comprehensively.