Evaluation of Weed Management Strategies on Grain Sorghum Nitrogen Status and Grain Yield Using Active Optical Sensors.

Grain sorghum has the most limited information on weed ecology and management options and relation to nutrient status. The objectives of this study were: (i) determine the effects of different weed management strategies on grain sorghum yield; and (ii) evaluate the impact on nitrogen (N) status and development of the crop based on these strategies using active optical sensor at key growth stages. This study was established at two locations in 2014 (Smith and Reno Co in Kansas). The study used a factorial design in a randomized complete block with 4 replications. The two main factors included N management and weed management for a total of 8 treatment combinations plus a control. Sorghum plant sampling was completed at growth stage 3 for biomass and nutrient content. Weed biomass was collected at growth stage 3 for sorghum and at time of harvest. Harvest was completed form the middle two rows and evaluated for grain yield, test weight and N content. The Trimble greenseeker was used at key stages to evaluate NDVI associated with the treatments. Results show significant difference in nutrient uptake with different weed species, and affecting nutrient uptake in the sorghum crop. Weed management approach and N application time showed a significant effect on sorghum growth and nutrient uptake.