Effects of irrigation and nitrogen application rates on nitrate nitrogen distribution and fertilizer nitrogen loss, wheat yield and nitrogen uptake on a recently reclaimed sandy farmland

Author： Wang Qi Li Fengrui Zhao Lin Zhang Enhe Shi Shangli Zhao Wenzhi Song Weixin Vance Maureen

Publisher： Springer Publishing Company

ISSN： 0032-079X

Source： Plant and Soil, Vol.337, Iss.1-2, 2010-12, pp. : 325-339

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Abstract

Monitoring of drinking water has shown an increase in nitrate-nitrogen (NO ₃⁻ -N) concentration in groundwater in some areas of the Heihe River Basin, Northwest China. A combination of careful irrigation and nitrogen (N) management is needed to improve N uptake efficiency and to minimize fertilizer N loss. A 2-year experiment investigated the effects of different irrigation and N application rates on soil NO ₃⁻ -N distribution and fertilizer N loss, wheat grain yield and N uptake on recently reclaimed sandy farmland. The experiment followed a completely randomized split-plot design, taking flood irrigation (0.6, 0.8 and 1.0 of the estimated evapotranspiration) as main plot treatment and N-supply as split-plot treatment (with five levels of 0, 79, 140, 221, 300 kg N ha⁻¹). Fertilizer N loss was calculated according to N balance equation. Our results showed that, under deficit irrigation conditions, N fertilizer application at a rate of 300 kg ha⁻¹ promoted NO ₃⁻ -N concentration in 0–200 cm depth soil profiles, and treatments with 221 kg N ha⁻¹ also increased soil NO ₃⁻ -N concentrations only in the surface layers. Fertilizer N rates of 70 and 140 kg ha⁻¹ did not increase NO ₃⁻ -N concentration in the 0–200 cm soil profile remaining after the spring wheat growing season. The amount of residual NO ₃⁻ -N in soil profiles decreased with the amount of irrigation. Compared with N₀, the increases of fertilizer N loss, in N₇₉, N₁₄₀, N₂₂₁ and N₃₀₀ respectively, were 59.9, 104.6, 143.5 and 210.6 kg ha⁻¹ over 2 years. Under these experimental conditions, a N rate of 221 kg ha⁻¹ obtained the highest values of grain yield (2775 kg ha⁻¹), above-ground dry matter (5310 kg ha⁻¹) and plant N uptake (103.8 kg ha⁻¹) over 2 years. The results clearly showed that the relative high grain yield and irrigation water productivity, and relative low N loss were achieved with application of 221 kg N ha⁻¹ and low irrigation, the recommendation should be for those farmers who use the upper range of the recommended 150–400 kg N ha⁻¹, that they can save about 45% of their N and 40% of their irrigation water application.