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Small Grain and Corn Development: 2015 Growing Season (06/11/15)

Small grain acres were planted one to three weeks earlier this year than the long term average. Early planted small grains usually develop greater yield potential as the cooler temperatures normally encountered in early spring favor the development of more tillers and larger spikes.

Small Grain and Corn Development: 2015 Growing Season

Small grain acres were planted one to three weeks earlier this year than the long term average. Early planted small grains usually develop greater yield potential as the cooler temperatures normally encountered in early spring favor the development of more tillers and larger spikes. Additionally, wheat growing degree days (GDDs) this year are running 50 to 100 behind normal, further favoring high yield potential development. For the early planted small grain crops that had adequate moisture to establish a good stand and that have not suffered from waterlogging in recent days, the prospect at the point for very high yield is favorable. It would be my assessment that we have the potential for very good yields this year. Higher than expected yields usually means lower than desired protein. For wheat, some additional nitrogen might add some value to the crop by improving the protein content.

Much of the corn was planted before the first week of May. Planting corn early improves the chance that the crop will mature and dry down in good time in the fall. Unlike the small grains, however, corn yield potential is not been favored by this year’s abnormally cool spring. Corn GDDs are running about 30 behind the long term average, negating some of the beneficial effect of earlier planting on maturity. The dry soils early in the spring and then the wet cool soils later have negatively impacted corn stands in some fields With the recent warm weather, corn will start to green up as roots expand and have greater access essential nutrients. Excess soil moisture may be the most significant factor impacting yield development in corn to date.

Impacts of waterlogging

Waterlogging (flooded/ponded/saturated soils) has been common in many fields this year, particularly in heavy valley soils with minimal slope. Waterlogging affects a number of biological and chemical processes in plants and soils that can impact crop growth in both the short and long term. Plants need oxygen for cell division, growth and the uptake and transport of nutrients. The rate of oxygen depletion in a saturated soil is impacted by temperature and the rate of biological activity in the soil. Faster oxygen depletion occurs when temperatures are higher and when soils are actively metabolizing organic matter. With the recent warm weather, the negative impacts of excessive water will accelerate.          

Generally, the oxygen level in a saturated soil reaches the point that is harmful to plant growth after about 48-96 hours. Crops are more sensitive to waterlogging when they are still below the surface of the soil, so most of our crops are in a stage that can tolerate some period of waterlogging. In cases where the crops have fully canopied, evapotranspiration should hasten the elimination of excess moisture. Waterlogged conditions also reduce root growth and can predispose the plant to root rots, so the ultimate effect of excess moisture may not be known until late in the season. It is common to observe plants that have experienced waterlogging to be especially sensitive to hot temperatures and to display nitrogen and phosphorus deficiencies later in the season due to restricted root development. Waterlogging can also impact the availability of nitrogen in the soil. Excessive water can leach nitrate nitrogen beyond the rooting zone of the developing plant, particularly in well-drained lighter textured soils. In heavier soils, nitrate nitrogen can be lost through denitrification. Research conducted in other states found losses from denitrification between 1 and 5% for each day that the soil remains saturated.

plsc.ransom.waterlogging

Joel Ransom

Extension Agronomist for Cereal Crops

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