Drought: Fertilizing for the next crop
Drought. The impact on crop production has been sobering, but more than yield has been affected. The cycle of every nutrient has also been impacted. This year, taking measurements is more important than ever in 4R Nutrient Stewardship programs.
Compared to seasons with normal rainfall, residual soil nitrate can be higher after a drought where N was applied to a cereal crop. Higher levels arise from decreased downward movement of soil water and from reduced fertilizer N uptake by the drought-stressed plant.
Whether or not residual N will be available for next season’s crop depends greatly on the precipitation that occurs after harvest. In the Midwest, precipitation occurring early in the following season is associated with higher losses of nitrate in tile drainage. Soil nitrate tests are the best tool for assessing the quantity of residual soil N available to the next crop. Additionally, cover crops can be planted after harvest to take up some of the residual nitrate and protect it from environmental losses.
In many areas, crops originally intended for grain harvest were cut instead for forage. The change from harvesting grain to harvesting most of the aboveground portion of the plant changes how much of each nutrient is removed. If grain was harvested as planned, grain nutrient concentrations of drought-stressed crops may or may not differ from unstressed plants, depending on the crop as well as the timing and severity of water deficits. Tissue testing of harvested crop portions is essential this year to determine changes from planned nutrient removal. This is especially important for P and K.
Very little data exist on how N credits are affected for cereals grown after legumes under drought conditions. If drought occurred during the growth of the legumes, it is hypothesized that more residual nitrate will exist in the soil, since legumes often scavenge soil nitrate under normal growth. How drought affects the amount of readily mineralizable N from root exudates is not well quantified. However, legumes are regularly used in arid areas to provide N to cereal crops, so it seems reasonable to take some to all of the N credit used normally.
Soil tests after a drought may contain some unexpected variance when compared with tests from more normal years. The immobile nutrient most sensitive to environmental conditions during sampling is K. Lack of rainfall reduces the leaching of K from plant tissues prior to sampling, which can reduce soil test results. Additionally, soil mineralogy can either increase or decrease the amount of available K under drought conditions. Taking soil samples in a drought year and looking at the changes can provide valuable data for improved interpretation in future years when dry conditions strike again.
The impacts of drought on crop nutrition are profound. Soil testing and plant analysis remain our best tools to quantify these impacts to adjust nutrient management for the next crop. Discussing analytical results with a trusted and knowledgeable agronomist ensures informed strategies can be created to meet local conditions.
For more information from IPNI on nutrient management following a drought, visit http://www.ipni.net/.
- DuPont Crop Protection to sell certain assets to Bayer
- New research study shows the value of neonicotinoids
- Alltech Crop Science acquires South African distributor
- Monsanto invests to transform plant breeding
- Fungicide-resistant soybean diseases spreading
- Most crop futures are starting Thursday on a strong note
- ValueAct buys stake in fertilizer dealer Agrium
- Critics of Dow herbicide sue U.S. EPA over approval
- Six tips to help professionals take leaps of faith
- Nitrogen fertilization rates for corn production
- Landmark Services Co-op, Curry Seeds sign agreement
- No-till may not bring boost in global crop yields
- Los Angeles City Council votes to explore ban on GMO plants
- ASA issues statement on EPA’s neonicotinoid study
- Economist: Taxing P could reduce risk of algal blooms
- Commentary: Government wants farmers to quit farming
- Resistant weeds not controlled by fall residuals
- First responders need to prepare for agroterrorism