Yield responses of the main cereal crops to the application approaches and rates of zinc fertilizer in China

【Objectives】The application of zinc (Zn) fertilizer is an effective measure to solve Zn deficiency and to improve both yield and grain Zn content in cereal crops. The effects of Zn application are affected by many factors. The effects of Zn application approaches and rates on the yield of wheat, maize, rice since the 1970s in China were summarized to explore an optimized approach and rate of Zn fertilizer in production systems of cereal crops. 【Methods】The data was collected from WanFangDATA and CNKI, including 333 literatures about the effects of Zn application on the production of wheat, maize and rice from 1970 to 2013 in China under field conditions. 1656 test samples were selected by excluding the literatures without yield data and specific fertilizer information such as a concrete application approach and rate of Zn fertilizer. Data was analyzed by correlation analysis and analysis of variance using Microsoft Excel 2010 softwares. 【Results】The positive effects of Zn applications on the crop yields were affected by application approaches and rates of Zn and different years. The main results were as follows, 1) Effects of Zn application methodsThe average yield increase induced by application methods such as soil, foliar and seed-treating applications of Zn fertilizer were 11.3%, 10.0%, 11.1%, respectively for wheat, 13.7%, 12.7%, 12.1% for maize and 15.0%, 9.8%, 9.7% for rice. Compared with foliar and seed-treated applications, soil application of Zn consistently achieved the highest yield increase regardless of crops. 2) Effects of Zn application ratesWith increases of soil Zn-applied rates, the average yield increase of wheat, maize and rice tended to increase continuously. When the soil applied Zn reached a certain amount, the yield increase showed a slight decrease. The optimized soil Zn-applied rates for higher increases in yield of wheat, maize and rice were 15-45 kg /ha, 20-30 kg/ha, and 20-30 kg/ha, respectively. The foliar applications of Zn showed an irregular effect on the yield increase of wheat, with foliar application of ZnSO47H2O at a 0.4%-0.5% rate achieving the highest yield increase. The effects of foliar applications of Zn on yield increase of maize and rice are the same as soil applications of Zn. In the past 40 years, the optimized foliar Zn-applied rates in form of ZnSO47H2O for maize and rice were 0.1%-0.3% and 0.2%-0.4%, respectively. 3) Effects of different yearsThe yields in response to different crops were different with years. Advanced in years, the yield increase of wheat tended to increase continuously with each Zn application method. For rice, the yield increase induced by soil applications showed a slight decrease while it decreased slightly at first and then increased with foliar applications. In contrast to soil and foliar applications, seed-treating applications showed an irregular effect on the yield increase of maize, wheat and rice.【Conclusions】Zn fertilizer application could effectively improve yields of wheat, maize and rice, but the yield increase was affected by application approaches and rates of Zn fertilizer and different years. Therefore, in the future, farmers should choose an appropriate method and rate of Zn fertilizer to improve yields of cereal crops based on the crops, soil and environmental conditions.