Balanced Nutrition and Crop Production Practices for Closing Grain Sorghum Yield Gaps.

Mid-west grain sorghum (Sorghum bicolor (L.) Moench) producers currently face low attainable yields, therefore, closing yield gaps will increase productivity. Yield gaps are the difference between maximum yield and attainable “farmer” yield. Maximum yield can be achieved through the optimization of utilizing the best genotypes and management practices for the specific site-environment (soil-weather) combination. This project examines several management factors in order to quantify complex farming interactions in nutrient partitioning and for maximizing sorghum yields. The factors that were tested include narrow row-spacing (37.5 cm) vs. standard row-spacing (75 cm), high (197,600 pl/ha) and low (98,800 pl/ha) seeding rates, balanced nutrient management practices including applications of NPK and micronutrients (Fe and Zn), crop protection with fungicide and insecticide, plant growth regulator effects, and the use of precision Ag technology (precision N application). This project was implemented at four locations in Kansas during 2014 (Rossville, Scandia, Ottawa, and Hutchinson). Results from Rossville show that when water is not a limiting factor (e.g. irrigated), yield variability was minimized. The greatest yield difference (1318 kg/ha) was documented between ‘farmer practice’ (low input treatment) and ‘kitchen sink’ (high input treatment). Similarly, grain sorghum yields in Scandia under dryland conditions varied from 6465 to 7219 kg/ha for the low and high input treatments, respectively; although the treatment difference was not statistically significant. The Ottawa site experienced severe drought-stress during reproductive stages of plant growth, which resulted in low yields (averaging 4300 kg/ha) and was not influenced by the cropping system approach. When water was not limiting sorghum yields, a balanced nutrient application and optimization of production practices did increase grain sorghum yields (‘kitchen sink’ vs. ‘farmer practice’). Further evaluation of nutrient uptake and partitioning in different plant fractions should be investigated to better understand if high-yielding grain sorghum can be achieved via balancing nutrient applications and optimizing production intensity.