DECISION SUPPORT TO REDUCE THE NITROGEN YIELD GAP IN ORGANIC AGRICULTURE

One of the challenges that farmers face is deciding which fertilizers to use and how much to apply to their fields. Fertilizers provide essential nutrients for healthy crops and can increase yields and profits.Nitrogen is an important plant nutrient and component of most fertilizers.Too little nitrogen stunts crop growth, but too much can cause excessive weed pressure and nitrogen losses to the environment.Excess nitrogen in drinking water can make it unsafe for human consumption and excess nitrogen in lakes and streams can be detrimental to aquatic life and human recreation.Although most crops require supplemental nitrogen for optimum growth, some nitrogen can be supplied from the soil and plant residues.Some farmers grow cover crops from fall to spring and as these plants decompose, they can be a source of nitrogen.However, this existing fertility depends on soil and cover crop characteristics specific to each farm field.To date, no nitrogen decision support tool has enabled organic farmers to calculate the nitrogen that will be released slowly from the soil and decomposing cover crops on their fields during the growing season.Without this knowledge, organic farmers are left to use rules of thumb to estimate existing fertility, often leading to both over and under applications of fertilizer.We have developed an onlinetool that predicts corn yield based on the amount of nitrogen that is slowly released from the soil and decomposing cover crops.Using site-specific information, the tool calculates the amount of nitrogen needed to supplement the existing soil fertility and to achieve a goal for corn yield.Through this project we will expand the testing our tool to corn fields across Pennsylvania with a wide variety of soil types and cover crops.Also, we will use laboratory experiments to expand our understanding of how soil microbes slowly release nitrogen, making it available to plants. These laboratory studies will help us predict the conditions under which the model will work well.We will work with a small group of farmers to test the tool on their fields to make sure it is easy to use and helpful in making fertilizer decisions.We plan to improve the tool by adding the capability to compare the costs of different nitrogen fertilizer options, allowing farmers to consider profitability in their decision-making.Ultimately our goal is to provide a nitrogen decision support tool that assists organic farmers in choosing the optimal type and amount of fertilizer for their fields, maximizing profitability for farmers and improving environmental quality.