Wheat Variety Response to Intensive Vs. Standard Management Strategies to Narrow Yield Gap in the Southern Great Plains.

Farmer reported wheat (Triticum aestivum L.) grain yield in the southern Great Plains is ~3.5 Mg ha^-1 lower than the estimated yield potential of ~7 Mg ha^-1. Our objective was to determine the influence of genotype, environment, and management on grain yield to elucidate methods to decrease the wheat yield gap in the southern Great Plains. Field experiments were conducted in Chickasha, OK, from 2014 to 2016 and at three locations in KS in 2016 to evaluate genotype-specific response to nitrogen (N) and foliar fungicide. At each site, 35 to 50 winter wheat varieties were evaluated under standard management practice (SM) with N rate calculated for a yield goal of 5 Mg ha^-1, versus intensive management (IM) with an additional 50 kg of N ha^-1 applied at Feekes GS3 for yield goal of 8 Mg ha^-1 and two fungicide applications (Feekes GS6 and GS10). Yield gap between the IM and SM ranged from 0 Mg ha^-1 in OK 2014, when both IM and SM yielded ~3 Mg ha^-1 due to a severe spring drought, to ~ 2.5 Mg ha^-1 in OK 2016. Varieties more susceptible to stripe rust (Puccinia striiformis Westend) had 50% cumulative probability yield gain of 0.8 Mg ha^-1 in KS and 1.6 Mg ha^-1 in OK by switching from SM to IM, while resistant varieties gained ~0.25 Mg ha^-1 in KS and ~0.8 Mg ha^-1 in OK. The probability of breakeven was about two times greater in susceptible varieties as compared to resistant varieties both in KS (42% vs. 21%) and OK (72% vs. 43%). Our results indicate that selecting varieties with resistance to major fungal diseases can sustainably narrow the wheat yield gap in most years, reducing the need for additional fungicide. Notwithstanding, optimized management system is warranted for varieties that lack the aforementioned genetic resistance.