ZHANG Zhiyun1, 2, ZHAO Weixia1, LI Jiusheng1

1. China State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources and Hydropower Research, Beijing 100038, China
2. College of Water Resources &Civil Engineering, China Agricultural University, Beijing, 100038, China

Abstract: 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/hm2 were used. The experiments were conducted using a randomized complete block design (RCBD) with three replications and a total of 27 experimental plots were created. 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 cm 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.

Key words: irrigation frequency; nitrogen fertilizer; greenhouse; tomato; deep percolation; nitrate leaching

Published in: Journal of China Institute of Water Resources and Hydropower Research Vol. 13 No.2, April, 2015