Will an Intensive Management Strategy be the Answer to Close Winter Wheat Yield Gaps in Kansas?.

Average Kansas wheat yield had never surpassed 3.36 Mg ha^-1 until 2015-16 and was nearly plateaued for 30 years. Our objective was to quantify the contribution of individual management practices in closing wheat yield gaps. Fourteen treatments were established in an incomplete factorial treatment structure conducted in a randomized complete block design with six replications in three locations in central Kansas during 2015-16. Individual management practices were added to a standard (SM) or removed from an intensive (IM) management approach to determine their effect on grain yield. Practices were nitrogen (topdress or split-topdress 134 or 269 kg ha^-1), sulfur (45 kg ha^-1), chloride (45 kg ha^-1), plant population (84 or 138 kg ha^-1), fungicide (with or without Approach at Feekes GS6 and Approach Prima at GS10.5), and plant growth regulator (with or without Palisade). A cool and moist spring lead to high stripe rust (Puccinia striiformis f.sp. tritici) incidence and severity. The IM increased yield (4.4 vs. 3.1 Mg ha^-1), test weight (74 vs. 71 kg hL^-1), and protein concentration (14.7 vs. 13.5%) across site-years compared to the SM. Fungicide added to the SM improved it to similar levels of those in the IM for grain yield, test weight, and grain moisture in Belleville (5.3 vs. 5.51 Mg ha^-1; 76 vs. 75 kg hL^-1; 12.5 vs. 13.2%) and in Hutchinson (3.73 vs. 3.85 Mg ha^-1; 71 vs. 72 kg hL^-1, and 8.4 vs. 8.6%). Orthogonal contrasts indicated that split-nitrogen (3.5 vs. 3.3 Mg ha^-1) and plant population (3.6 vs 3.4 Mg ha^-1) increased grain yield under no-till in Manhattan. Split-nitrogen increased protein concentration at all locations and fungicide increased it at Hutchinson and Manhattan. These results suggest that an IM strategy might be less economical than integrated pest management to close wheat yield gaps in Kansas.