ABSTRACT
Soil testing has been promoted and used as a means of fertilizer recommendations in China and has helped to increase maize grain yield and NUE. Soil test-based fertilizer recommendation in smallholder systems poses several challenges and uncertainties, including taking representative soil samples, identifying a suitable analytical method and establishing a good correlation and calibration between soil test value and crop response. Besides being labour-intensive and time-consuming, the challenge of selecting a sciencebased fertilizer recommendation philosophy to use with the soil test data often affects the outcome. An alternative method of fertilizer recommendation is using the NE for maize. In China, NE was developed based on analysis of relationships among yield response, indigenous nutrient supply, agronomic efficiency and relative yield from datasets collected from 2001 to 2010. The tool was developed to help crop advisors from the public and private sector as well as scientists and extension specialists in large-scale implementation of site-specific fertilizer recommendations. On-farm field validation was conducted in 408 farmers’ fields located in Hebei, Henan, Shandong, Shanxi, Jilin, Liaoning and Heilongjiang provinces in 2010-12 to test the efficacy of the NE in different growing environments of China (Xu et al., 2014). Results indicated that NE recommendations matched the yield and profit of farmers’ practice (FP) in six of the seven provinces and exceeded the yield and profit in the seventh province. The NE tool reduced N application by 67.8 kg ha1 (30.2%) and P2O5 by 7.0 kg ha
compared with FP across all sites. The average gross profit over fertilizer cost in the NE recommendation was 3049 US$ ha1 compared with 2928 US$ ha1 in FP for all sites, and gross profit improved from 22 to 276 US$ ha1 with an average of 121 US$ ha1 (4.1%). Fertilizer recommendation based on NE significantly improved N use efficiency compared to FP for each province (P 0.05). The average AEN, recovery efficiency of N (REN) and PFPN for NE were 12.2, 0.302 and 65.7 kg kg1 as compared to corresponding values of 8.3, 0.200 and 48.5 kg kg1 for FP. The results showed that fertilizer recommendations based on the NEtool could maintain grain yield and profitability and improve NUE through 4R nutrient stewardship. Considering the ease of use, and its applicability in diverse maize-growing areas in China, the Nutrient Expert® tool is a promising approach for optimizing nutrient use in maize when soil testing is not timely or not available.
