Fertilizer events can be entered for each planting to track how much fertilizer was used to produce a crop. Additionally, CropManage can recommend a nitrogen fertilizer rate for a vegetable crop based on the nitrogen uptake rate, current soil nitrate status, and nitrate concentration of the irrigation water. CropManage will also adjust the recommended rate for the estimated N mineralization from the soil organic matter and previously incorporated crop residues.
Soil nitrate measurements during the cropping season are especially useful for understanding how much nitrogen fertilizer is needed for vegetables. Ideally, the soil should be sampled within a few days of the planned fertilizer application. Since soil nitrate can readily leach with percolating water, any irrigation events between soil sampling and fertilizing could affect the nitrate level of the soil.
To enter a new fertilizer event for a planting select the “+” icon on the upper left-hand corner of the planting summary card.
Enter the date of the fertilizer event and choose a fertilizer from the fertilizer list. Note that this list can be customized in the ranch settings. Enter the days to the next fertilization. It is important to enter an accurate fertilization interval (days to next fertilization) because CropManage uses this value to estimate the N requirement of the crop. Next one can optionally select a crop stage to associate the event with the developmental or cultural stage of the crop. Select “add” to save the event and see the recommended fertilizer rate.
The recommendation will display a recommended nitrogen fertilizer rate in fertilizer units (gallons or pounds of fertilizer per acre) or in nitrogen units (pounds of nitrogen per acre).
The recommendation can be adjusted for a soil nitrate value or the concentration of nitrate in the irrigation water. To add a soil sample select the appropriate value from the drop-down list of samples that were entered for the planting. A new sample can also be entered.
After selecting the soil nitrate value the fertilizer N recommendation is automatically adjusted.
Crediting the nitrate (or urea and/or ammonium for water with organic N sources) in the irrigation water can further refine the fertilizer recommendation. Choose “include N contribution in water.”
There are two ways to enter the nitrate or N concentration of the irrigation water. The value can be entered manually or from the water source values that were entered when setting up the ranch. If several water sources are blended, the percentage of water from each source needs to be entered and the values must sum to 100. Either enter the applied inches or hours of irrigation or CropManage can estimate the volume of water that the crop will use over the fertilizer interval. The estimated N contribution from the water is displayed in fertilizer or N units and can be subtracted from the fertilizer recommendation by selecting “update recommendation with N contribution.”
The “i” icons provide more information about the irrigation volume and N contributions from the water
A summary of the N fertilizer recommendation can be viewed by selecting “Recommendation Summary.” This is an opportunity to check that the inputs to the estimate and the fertilizer interval are accurate. The summary also shows the nutrient budget equation used for estimating the fertilizer recommendation.
Finally, the farm manager can use the CropManage recommendation to enter their own recommendation. This value should be entered in the text box labeled “manager.” Important: when satisfied with the recommendation, select save. The last user to update the fertilizer event is displayed below the Fertilizer N applied text box. Only fertilizer amounts entered as Fertilizer N applied are counted as applied fertilizer.