Optimizing Crop Nutrition
Basic science reveals that soils provide the foundation of crop nutrition. Crops provide the chemical energy required through photosynthesis to feed soils with residues and root exudates. Diverse soil microbes, living in, on, and around those roots use that chemical energy to release mineral nutrients into solution. Crops, microbes, and other soil life then use those nutrients to live, grow, and continue the cycle of life.
So, why add fertilizers? If they are needed, how does one optimally apply them?
The 5Rs of Crop Nutrition
In order to optimize nutrient use efficiency, rate, timing, placement, form, and product of all nutrients applied is necessary. Ag Spectrum’s Crop Recommendations and crop timelines provide details for all types of fertilizer applications. At the most basic level, our recommendations provide crop plants with enough added nutrients to overcome reliably predictable crop stresses that occur in most soils in most years regardless of location.
The Maximum Farming System involves optimizing both soil health and crop nutrition. To be most successful, Associates work with customers on a field-by-field basis, being mindful of both the natural environmental constraints and the operational limitations of farmers.
This is how Ag Spectrum leads farmers to greater success.
Mineralization is Limited
While soils have ample element supplies to support crops, they are not always sufficiently available to maximize growth. The balance of soil moisture and temperature is never optimal throughout the growing season. Knowing how and why soils are unable to meet crop demand is central to optimizing when, where, and what fertilizer to use.
Early in the season, cool temperatures and excessive moisture can limit crop and soil activity, but the limitation is greater below ground when water limits oxygen availability and slows soil warming. Adding Ag Spectrum’s GroZyme® pre-plant or in furrow can stimulate greater soil microbial activity in cool, moist soils, jumpstarting processes in advance of warming temperatures.
In corn, the complete and well-balanced nutrition from Clean Start® and Kick-Off® ensures the emerging crop has enough plant-available nutrients to take it through V6; the point when soils are typically warm enough to provide most crop needs.
As summer progresses, soil temperatures can exceed optimums for plant growth, and moisture near the surface can become limiting. Nutrients in dry soils, especially the micronutrients needed for healthy pollination, can become yield-limiting. By efficiently applying Score® with PT-21® as a foliar treatment, sufficient micronutrients are available to the crop during the critical transition from flowering into grain fill.
Pay Attention to Specific Crop Demands
Crops have specific demands during their lifecycles. For instance, corn responds significantly to early phosphorous levels by V3, which is why we recommend Clean Start in furrow at specific rates. This ensures sufficient plant-available phosphorus to maximize kernel row count. By combining the orthophosphate in Clean Start with GroZyme and the right balance of other nutrients in furrow, that P can be used more efficiently, further reducing the rate required to achieve maximum yield potential.
In contrast, germinating legumes like soybeans and alfalfa seed are more salt sensitive than corn and wheat. So, in furrow applications of Clean Start must not exceed certain low levels (e.g., 1 gal/ac Clean Start in most soils with CEC >14). However, elevated levels of balanced early nutrition can be safely delivered as a foliar spray of Clean Start/Kick-Off/GroZyme once those legume crops reach a certain size (e.g., V3-V5), a point at which the applied potassium rates are not likely to stress the crop should soils become dry unexpectedly.
Additionally, crops grown in fields where glyphosate is applied will experience greater micronutrient limitations. Both the glyphosate-containing herbicide and its initial breakdown product, AMPA, make micronutrients, especially Mn, less available to plants and some microbes. Foliar applications of Glycure® with PT-21 and GroZyme provide the needed micronutrients to the crop and stimulate more rapid decomposition of the herbicide in the process.
As plants proceed through their reproductive phases, increasing root activity will increase yield potential. Indeterminate crops, applications of PT-21/Score/GroZyme will stimulate new root growth following pollination and on into the early grain fill stages (e.g., through completion of R3).
Nitrogen availability during grain fill is critical to maximizing yield potential. In corn and wheat, the goal is for just enough N fertilizer to contact the root zone as late in the season as is practical. Rates should be proportional to crop or hybrid demand and late season soil water availability.
In soybeans and alfalfa, particular attention to improving the air and water balance of soils is needed to maximize late season nodulation which supports grain fill.
-submitted by Dr. Brian Gardener, Technical Director