Agronomic Research Updates

Jarrod O. Miller, Extension Agronomist,

The Effects of Nitrogen Fertilization on Corn Residue Decomposition
To increase corn residue decomposition, Iowa farmers may apply liquid N following harvest. A study of two fields with three N rates did not observe any effects on corn fodder breakdown with additional N. Lab studies revealed that temperature drove corn fodder breakdown more than applied N. Agronomy Journal (109): 2415-2424.

Can Yield Goals Be Predicted?
Wheat yields averaged over the previous 3-5 years were not correlated with the ensuing yield, mainly due to varying weather conditions. Because optimum N use may change every year, active sensors (e.g. Greenseeker) at mid-season are a viable alternative. Agronomy Journal (109): 2389-2395

Soil Potassium Levels and Depth to a Clay Pan
Soils in Missouri have varying topsoil thickness and depth to claypans. Soils where claypans were deeper in the profile required more K to raise to soil test potassium. Checking soil maps for depth to clay layers may help predict K losses on the Delmarva as well. Agronomy Journal (109): 2291-2301

Starter N and Cover Crops in Organic Corn
Cereal rye and hairy vetch were fall planted and then terminated with a roller crimper in the spring, prior to corn planting. This mixture could produce a high biomass capable of suppressing weeds. Starter fertilizer in the form of poultry litter or feather meal was necessary to maximize organic corn yield in this cover crop system. Agronomy Journal (109): 2214-2222

Variability in Corn Yield Response to Nitrogen
Planting at optimal dates resulted in less variable optimum economic N rates, compared to those that were planted late. On coarse textured soils, more N was needed with wet growing seasons. Agronomy Journal (109): 2231-2342)

Wheat Production and Nitrogen Additives
The combination of urease and nitrification inhibitors was successful at reducing N losses as ammonia or nitrous oxide, compared to urea alone. Higher nitrous oxide losses were observed when pore water was 35-60%, soils were warmer than 50°F and there was adequate soil nitrate. Both inhibitors reduced the nitrate concentrations below the root zone. Agronomy Journal (109): 1825-1835.