Variable rate nitrogen application algorithm based on SPAD measurements and its influence on winter wheat

The objective in this study was to develop the time-specific and time-critical method to overcome the limitations of traditional field sampling methods for variable rate fertilization. Farmers, agricultural managers and grain processing enterprises and interested in measuring and assessing soil and crop status in order to apply adequate fertilizers quantities to crop growth. This paper focused on studying the relationship between SPAD readings and crop chlorophyll concentration and/or nitrogen content to determine the amount of nitrogen fertilizer recommended for variable rate management in precision agriculture. The recommended rate of conventional uniform rate fertilizer management was higher than that of variable management. The grain yield, ear numbers, 1000-grain weight and grain protein content were measured between CK and variable rate fertilizer treatments. It indicated that variable rate fertilization reduced the variability of wheat yield, ear numbers and 1000-grain weight, but it didn´t increased crop yield and grain protein content significantly, compared to traditional nitrogen application. The nitrogen fertilizer use efficiency was improved, for this purpose, the variable rate technology (VRT) based on SPAD readings could be used to prevent the water pollution and environmental deterioration