Optimal cattle manure application rate to maximise crop yield and minimise risk of N loss to the environment in a wheat-maize rotation cropping system

Yongping Jing1,2, Yan Li1,2,4, Yingpeng Zhang1,2, Jiafa Luo3, Luji Bo1,2, Ming Sun1, Ziwen Zhong1

1 Institute of Agricultural Resources and Environment, Shandong Academy of Agricultural Sciences, Jinan 250100, China

2 Key Laboratory of Agro-Environment in Huang-Huai-Hai Plain, Ministry of Agriculture, Jinan 250100, China

3AgResearch Research Ruakura, 10 Bisley Road, Hamilton 3240, New Zealand

4Corresponding author: [email protected]

Abstract

This paper examines the effect of cattle manure application rates on nitrate nitrogen (NO3-N) migration and accumulation in a farmland soil and investigates methods for appropriate manure use in order to reduce NO3pollution to the environment. A field experiment was conducted on a fluvo-aquic soil in a cropping area of Caoxian County in Shandong Province, China. The effect of cattle manure (with N concentration of 1.5%), at different application rates (0, 15000, 30000, 45000, 60000 and 75000 kg/ha/year), on vertical distribution of soil NO3-N, crop yields, and nitrogen use efficiency was determined in a winter wheat and summer maize rotation on farmland under natural rainfall conditions. The results showed that the NO3-N concentrations in the soil profile (0-100 cm) increased with the increase in application rate. When the rate was greater than 45000 kg/ha/year, soil NO3-N concentrations were significantly higher than those in the other treatments with lower application rates. The NO3-N levels in the 80–100 cm soil layers were several times higher than those of the surface soils at the later growing stage of the winter wheat in early summer, indicating that this NO3-N, which had migrated downward and accumulated in the deep soil would be prone to drain to groundwater during the summer rainfall season, as it would be below the root zone of the summer maize. A quadratic relationship between crop yields and cattle manure application rates was found. Wheat and maize silage yields were highest when cattle manure application rate was 45000 kg/ha/year, with the N use efficiencies of wheat and maize silage both being about 50%. We conclude that a cattle manure application rate of 45000 kg/ha/year (equivalent to 675 kg N/ha/year) is optimal for this wheat-maize rotation cropping system.