HE Ping
Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, International Plant Nutrition Institute China Program

Fertilizer has played a crucial role in maintaining food security in China. However, over and imbalanced fertilization has resulted in lower fertilizer use efficiency and resources waste, and caused potential environmental issues.The Nutrient Expert (NE) for wheat and maize is a decision support system being developed by the Institute of Agricultural Resources and Regional Planning, CAAS, and International Plant Nutrition Institute (IPNI), with the goal of supporting advisors who make fertilizer recommendations to farmers. The Nutrient Expert system uses site-specific nutrient management (SSNM) principles, which include the use of the Quantitative Evaluation of the Fertility of Tropical Soils (QUEFTS) model to determine crop nutrient uptake requirements. SSNM was initially used for rice in the mid-1990s as an alternative approach for dynamic management of nutrients, and to optimize supply and demand of a nutrient within a specific field in a particular cropping season. The QUEFTS model was originally developed by Janssen et al. (1990) and was transformed and validated to estimate the optimum nutrient requirement at a target yield. The core of the fertilizer recommendation method in Nutrient Expert is based on yield response and agronomic efficiency (AE). The yield response to N, P or K is the yield gap between NPK plots that received ample nutrients and omission plots when one of the nutrients is omitted. The agronomic efficiency of N, P or K (AEN, AEP or AEK) is the yield increase per unit of fertilizer N, P2O5 or K2O applied. Fertilizer recommendation based on yield response and agronomic efficiency is an alternative approach developed for use when soil testing is not available, also considers the N, P and K interactions. The determination of fertilizer N requirements from Nutrient Expert has been modified to use a target agronomic efficiency and an estimation of yield response to applied N. The determination of fertilizer P and K requirements considers the internal nutrient efficiency combined with estimates of attainable yield, nutrient balances, and yield responses from added nutrient within specific fields. This method utilizes soil indigenous nutrient supply in an attempt to avoid excessive nutrient accumulation in the soil and has been applied with success in rice,maize and wheat crops in some Asian countries.
Results from using NE in China have revealed that many farmers are over using N and P fertilizer, a fact which has been described in the scientific literature. We also have found that K remains one of the limiting nutrients in optimizing food grain yields in many regions of China. By reducing N and P use on most farms, and increasing K use, we can see an improvement in yields, as well as nutrient use efficiency. In the end this means better profits for farmers, and less nutrients left in the environment. The results of multiple field experiments helped to validate the feasibility of the recommendation model and concluded that Nutrient Expert could be used as an alternative method to make fertilizer recommendations in China when soil testing is not timely or not available.