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Agronomic Sheet Timely Grain Harvest What you need to know It’s more important to save yields than to save on drying costs. It’s time to start thinking about harvesting your corn. With the cool, wet start to the summer followed by a dry period in August, we need to be on the watch for lodging and stalk rots. PHYSIOLOGY OF STALK CANNIBALIZATION Corn plants must produce enough carbohydrates (sugars) by photosynthesis to meet the demands of grain fill plus keep the cells in both the stalk and roots alive. When the corn plant is subjected to drought stress during grain fill, the photosynthetic activity is reduced and the result is that there are insufficient carbohydrates for the developing ear. The corn plant responds to this situation by removing carbohydrates from the leaves, stalk and roots and uses them to fill the grain. This is referred to as cannibalization of the corn stalk. This process ensures a supply of carbohydrates for the developing ear, however, the removal of carbohydrates from the stalk results in a rapid deterioration of the lower portion of the plant with lower leaves appearing to be nitrogen stressed, brown and/or dead. This weakening of the stalk makes the plants vulnerable to lodging and also predisposes the plants to root and stalk infection by fungi such as Gibberella, Collectotrichum (anthracnose) and Fusarium. Other plant stresses which increase the likelihood of stalk problems include: •Loss of leaf tissue due to foliar diseases (such as grey leaf spot or northern corn leaf blight), insects or hail •Injury to the root system by insects or chemicals •High levels of nitrogen in relation to potassium •Compacted or saturated soils restricting root growth •High plant populations With cannibalization and stock lodging an issue this year, growers need to be monitoring grain moisture. It’s important to start monitoring grain moisture as soon as physiological maturity (black layer) is reached. Corn moisture at black layer should be around 30%. Allowing corn to dry too long in the field increases the risk of lodging, yield losses and stalk rots. When cannibalization is a problem during the growing season, the risks increase. Temperature, humidity, weather and grain maturity influence grain drying rates. Warm, dry weather speeds up the crop drying rate; cool, wet weather slows down the drying rate. Successful grain harvests can be accomplished when grain moisture is 28% or lower, and it is more important to maintain yields by harvesting at higher moisture than to try to minimize drying costs by leaving your fields at risk to yield robbing lodging or stalk rots1. When 10-15% of plants are found to lodge or are rotted, consider early harvest for that field. Fields that experience 2 or more of the causes of stalk cannibalization are good candidates for monitoring and early harvest. ECONOMIC EFFECT OF LODGING Lodging not only makes harvesting difficult, but it has an effect on your pocketbook as well. OMAFRA research found that 5% lodging loss could cost $35-40 per acre (based on 160‑200 bu/ac yield, $4.50/bu corn)2. This loss would pay to dry 4-5 points of moisture per acre of corn production. SCOUTING FOR LODGING AND STALK ROT There are two methods for scouting for lodging and stalk rots that can help determine if early harvest is necessary. For either method, select 20 plants from five different locations in the field for a total of 100 randomly selected plants. 1.Push Test – the top portion of each plant is pushed 15-20 cm (6-8 in) from the vertical. Number of lodged or broken plants is recorded. 2.Pinch or Squeeze test – the area above the brace roots is squeezed. This is particularly useful for identifying plants with stalk rot. The number of stalks that can be compressed is recorded. Push Test Lodged Corn 1 lmore, R and L Abendroth. 2010. Impact of in-field drydown rates on corn E harvest. Iowa State U. www.extension.iastate.edu 2 OMAFRA 2015 Field Crop Budgets Visit DowSeeds.ca for more information or follow us on Twitter @DowSeedsCA Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow. 10/15-44651-35 ® TM