Four Rs are the cornerstones of successful fertilizer application: the Right Material, applied at the Right Time, in the Right Amount, and to the Right Place. In the last several weeks, troubleshooting with growers and others about under-performing squash, sweet corn, tomato, and watermelon crops led us to conclude that incorrect fertilizer application rates were probably to blame. The information available suggested that too little fertilizer had been applied to the squash and sweet corn while too much had been applied to the tomato and watermelon plantings.
Ohio growers produce many different vegetable crops, each with a farm-specific fertilizer program that is best or most “right” for them. Very important, those fertilizer needs are set by the biology of each crop and its growing conditions and market. Crops, growing conditions, and markets are diverse, and that calls for setting and monitoring fertilizer applications very carefully; material, timing, rate, and placement must be optimal to have the best chance of success.
Errors at each step in the application process from selecting the rate to applying the material can lead to under- or over-applying fertilizer. For example, target rates can be miscalculated. Hoppers and injection tanks can be under- or overloaded. Gears, valves, and other equipment can be poorly calibrated or malfunctioning. Applicators/spreaders can be driven over too much or too little ground. Irrigation and/or injection valves can be closed when they were supposed to be open or vice versa.
Overall, some appear to worry less about applying too much instead of too little fertilizer. Their desire to maximize yield and quality is understandable. That said, the consequences of significantly over-applying fertilizer should also be considered since they may be wider ranging and last longer. Applying too much fertilizer in one season can create the problems of under-application in that season (lost yield, quality, and income) while also complicating fertilizer programs in the following season(s), supporting unwanted changes in soil chemistry, and contributing to other issues. Benefit the most from investments in properly selected fertilizers by applying them at the right rates and times and to the right place.