Evaluation of Simulated Corn Yields Across Nebraska in 2013 - UNL CropWatch, August 16, 2013
August 16, 2013
Model Indicates Grain Fill Could Take10-17 More Days in the Northeast
Across Nebraska, the 2013 corn season has been marked by considerable late planting (due to rain and a low spring temperature) and a cooler than average summer so far. This has led many to wonder about the effects of these conditions on corn yield and the possibilities and consequences of frost damage before the crop reaches maturity.
Table 1. Locations, corn hybrid maturities (RM), and planting dates used in the corn yield evaluation of 2013.
To answer these concerns, we used Hybrid-Maize (http://hybridmaize.unl.edu/), a corn simulation model developed by UNL scientists, to evaluate possible corn yield outcomes as well as the probabilities and consequences of frost damage. The evaluation is based on
- this year’s average and late planting dates (Table 1) as reported by UNL extension specialists and educators for different areas of the state,
- up-to-date weather data at selected locations (Table 1), and
- long-term historical weather data (26 years on average) at those locations.
All weather data are provided by the High Plains Regional Climate Center. Yield evaluation is made for both fully irrigated and rainfed crops when growth and yields are not limited by nutrient deficiencies, weeds, insect pests or diseases. (This is called yield potential.) Because of the variations in actual crop management, including planting date, hybrid maturity, seeding rate, fertilization, etc., simulated yield expectations are presented as percentage of simulated long-term average yield (Figure 1).
Figure 1. Expected corn yield potential based on 2013 average and late planting dates for fully irrigated fields. (All charts link to larger versions.)
Figure 2. Expected increase in the number of days for corn grain filling for average planting dates relative to long-term average cases using the same planting dates (projected August 16, 2013).
Expected Yields for Fully Irrigated Fields
For fields that were planted around the average planting date for each site, expected yields are 5-10% higher than simulated long-tern averages using the same planting dates (Figure 1). For fields planted around June 1, however, expected yields are 0-13% lower than simulated long-term averages using the same late planting dates. For fields with average planting dates, the expected higher yield potential this year is due primarily to the cooler summer temperature so far and, as a result, extended days for grain filling if the remaining weather is like an average year (Figure 2). For fields that were planted as late as June 1, expected lower yields result from the late season lower temperature and dramatic increase in probability of frost damage before the crop reaches maturity (Figure 3).
Expected Yields for Rainfed Fields
Soil water recharge rate at planting is one of the important factors that determines crop yield in rainfed systems. For all locations, we assume a silty clay loam soil where the top one foot of soil was recharged to field capacity while subsoil was recharged only to ¾ of soil available water due to the severe drought last year. The maximum rooting depth is assumed to be 5 feet at all locations. Other settings for these simulations were the same as for fully irrigated fields.
For fields planted on the average planting date at each site, simulated yields are considerably lower than an average year for most areas (Figure 4), but close to or higher than a normal year in northeast areas (Concord and Elgin) due to above average growing season precipitation. For fields planted June 1, simulated yields are also lower than an average year for most locations except where precipitation was above normal. Compared with irrigated fields, simulations of rainfed fields show much greater variation due to variation in growing season precipitation across locations. Likewise, due to large variability in rainfall amounts over relatively short distances in the state, there is greater uncertainty in making inferences about potential yields in areas nearby each of the rainfed locations simulated in this evaluation.
Figure 4. Simulated yield expectations of rainfed corn based on this year’s average and late planting dates (projected August 16, 2013).
In summary, yields for irrigated corn planted before or around mid-May across Nebraska could be 5-10% higher than an average year, due primarily to the relatively cooler summer temperature so far this year. For irrigated corn planted as late as June 1, yields could be 0-13% lower than an average year with the same hybrid maturity and late planning dates. For late planted corn, increased probability of frost damage is a concern.
For rainfed corn, expected yield potential could vary widely across the state. Many locations could see considerably lower rainfed yields than in an average year for both average or late planting dates because of insufficient water recharge in subsoil at planting. For rainfed fields in northeast Nebraska, however, rainfed corn yield could be close to or better than normal due to this year’s higher than average precipitation. We plan to update the corn yield evaluation regularly until end of the growing season.
Haishun Yang, Associate Professor, Agronomy and Horticulture
Charles Shapiro, Extension Soils Specialist
Jenny Rees, Extension Educator
Greg Kruger, Extension Crops Specialist
Patricio Grassini, Research Assistant Professor, Agronomy and Horticulture
Ken Cassman, Professor, Agronomy and Horticulture