Back to Contents6.2.3 Site-Specific Management of Banded Phosphorus/Potassium Applications
Investigators: John Grove, Ed Perfect and Tom Mueller
As farms become larger, equipment management necessitates that spring planting begin as soon as possible. At times, the weather can later become less than favorable for crop development, resulting in a slow start for early planted crops, particularly under no-tillage establishment conditions. Pop-up and/or starter fertilizer applications have been proposed to alleviate some of the early season nutrient stress often observed in such situations, to improve crop stands, and to improve early plant development. This early season nutrient stress may not only be related to a low reserve of available nutrient in the soil, but also to conditions that hinder nutrient uptake by the crop’s developing root system, such as reduced aeration and cold temperatures.
Evaluating the agronomic effectiveness of these banded fertilizer applications is hindered by the fact that crop yield at the end of the season may be less related to early season growth problems than to climate and other stresses that become evident later in the season. However, modern corn cultivars, which respond to higher plant populations, are more likely to respond to inputs that maintain crop stands in the face of early season stress. In many regions, growers favor full-season cultivars, because of the generally greater yield potential of these varieties. Early season growth stress may delay maturity of these cultivars, causing reduced yields and greater grain moisture at harvest. And as fields in Kentucky are often topographically uneven, it is reasonable to assume that soil properties influencing early season aeration and temperature stress are unevenly distributed in the landscape. And though many farm fields have average soil test phosphorus and potassium levels that are adequate for crop production, suggesting that the nutrient stress observed early in the season is only temporary, these same fields often have areas with more modest nutrient availability.
The decision is simple; the grower either does or does not apply banded fertilizer at planting. But the crop’s response is likely to be complex, driven by the interaction between soil chemical nutrient availability and temperature and/or aeration stress on the developing root system. This suggests a input situation suitable for site specific management research. It is relatively easy to execute the decision to band (either on or off), but more difficult to guide the decision with an appropriate algorithm. Currently, corn growers make the decision to band fertilizer on a field by field basis. Confidence in precision agriculture would be built by research that first helps growers do a better job with a more easily executed decision. And because the crop’s ability to recover soil phosphorus and potassium is related to soil chemical and physical properties, a map of the spatial distribution of these properties should drive crop response to banded nutrition and the decision to apply banded fertilizer.
So, as soil properties are not distributed uniformly within fields, patterns in crop response to banding, following patterns in soil properties, are likely. The existence of any such pattern across a field needs to be confirmed in field research, but would suggest that a spatial management strategy that optimizes our knowledge of the soil properties driving any response to banding should have some utility. We propose to characterize the response of the target crop (corn, in this case) to banded phosphorus or potassium (depending on the range and spatial distribution in soil test phosphorus and potassium values) as a function of landscape position and site chemical and physical properties related to early season nutrient availability, aeration and/or temperature stress.
Sites with existing terrain information (via digital elevation mapping), targeted for corn production, would be utilized. This should facilitate collaboration and maximize resource use efficiency. An experiment, consisting of treatments with and without banded fertilizer application, would be imposed in areas of each field to cover the range in chemical and physical properties thought likely to influence crop response using simple replicated strip plot designs. Besides soil properties, the corn crop would be site-specifically evaluated for grain yield, plant population, and for early season nutritional and developmental stress.