The current Oklahoma State University Soil, Water, and Forage Analytical Laboratory (OSU) phosphorus (P) recommendations were developed for conventional tillage systems with P fertilizer incorporated in the soil. The rate recommendations were based on a sufficiency approach, and included a pH adjustment factor. Increased adoption of no-till (NT) management across the region has resulted in more surface application of fertilizer, without concomitant changes in OSU recommendations. In the 2014-2015 and 2015-2016 growing seasons, nine on-farm trials were conducted in north-central Oklahoma to evaluate current winter wheat (Triticum aestivum L.) P recommendations, and grain yield responses to fertilizer in both P-sufficient and P-deficient soils, and acidic or non-acidic conditions. Phosphorus fertilizer was recommended for eight of the nine locations, while responses were recorded at only five of those eight locations. The results indicate that OSU P recommendations, with a soil acidity adjustment factor, did not limit winter wheat grain yields in NT management. In addition, the application of 30 lb acre -1 P 2 O 5 offset the effects of soil acidity on P uptake regardless of the degree of acidity. Finally, OSU recommended P on some locations where there was no response, suggesting more work is needed to understand crop response dynamics and build recommendations with increased location specificity.

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Continuous corn (Zea mays L.) yield increases are required to promote economic development and support a larger population. Reducing the existing yield gaps is a potential strategy to accomplish this goal. The objective of this study was to evaluate yield trends, and gaps at different production levels in Mississippi using data from 2012 to 2021. Production levels considered were Mississippi yield contest (Yc), Mississippi State University hybrid testing trials under irrigation (Yp) and dryland (Yw), and actual yield (Ya) from USDA National Agricultural Statistics Service. Since 2012, Yc, Yp, and Ya are stagnant, and Yw has a nonsignificant positive trend. Averaged over 10 yr, a yield gap of 5.6 Mg ha−1 between Yc and Ya, 4.1 Mg ha−1 between Yp and Ya, and 2.0 Mg ha−1 between Yw and Ya were noted at state level. Existing yield gap underlines current production limitations and necessitates adoption of improved agronomic practices. Core Ideas In the last 10 yr, contest yield, potential yield, and actual yield in Mississippi have been stagnant. State level yield gap ranges between 2.0 to 5.6 Mg ha‐1 at different levels. Washington County showed the lowest (25.9%) and Lee County (48.8%) the highest yield gap in Mississippi.

Optical sensors have grown in popularity for estimating plant health, and they form the basis of midseason yield estimations and nitrogen (N) fertilizer recommendations, such as the Oklahoma State University (OSU) nitrogen fertilization optimization algorithm (NFOA). That algorithm uses measurements of normalized difference vegetative index (NDVI), yet not all producers have access to the sensors required to make these measurements. In contrast, most producers have access to smartphones, which can measure fractional green canopy cover (FGCC) using the Canopeo app, but the usefulness of these measurements for midseason yield estimations remains untested. Our objectives were to (1) quantify the relationship between NDVI and FGCC, (2) assess the potential for using FGCC values in place of NDVI values in the current OSU Yield Prediction Model, and (3) compare the performance of NDVI and FGCC-based yield prediction models from the collected dataset. This project, implemented on 13 winter wheat sites over the 2019-2020 growing season, used a range of nitrogen (N) rates (0, 34, 67, 101, and 134 kg N ha−1) to provide different levels of yield. Our results indicated that while NDVI and FGCC are highly correlated (r2 = 0.76), FGCC is not suitable for direct insertion into the current yield prediction model. However, a yield prediction model derived from FGCC provided similar estimates of yield compared to NDVI (Nash Sutcliffe Efficiency = −3.3). This new FGCC-based model will give more producers access to sensor-based yield prediction and N rate recommendations.

Placement of fertilizer in the seed furrow to increase nutrient availability is a common practice in row-crop production. While in-furrow application of fertilizer is widely utilized in the production of winter wheat (Triticum aestivum L.), there is a lack of work evaluating new formulations and nutrient combinations that are available. The objective of this study was to quantify the effects of in-furrow fertilizer products and combinations of products on winter wheat grain yield, nitrogen and mineral concentrations. Trials were conducted across five site-years in central Oklahoma using 11 fertilizer formulations placed in-furrow at the time of planting. In locations that soil test phosphorus (STP) levels or potassium were above sufficiency, the use of in-furrow fertilizers did not improve yield over the control. Inconsistency of response was noted at locations where STP levels were below the critical threshold. While one location showed no response to the addition of P regardless of source, two other locations had significant yield responses from three or more P-containing fertilizers. The addition of both sulphur and zinc resulted in increased yield over the base product at one low STP location. Nutrient concentrations were also influenced in nutrient-limited soils; however, no trends in response were present. Based upon the results of this study, the application of in-furrow fertilizer has the potential to increase winter wheat grain yield and nutrient concentration, when soil nutrients are limiting. As expected the addition of fertilizer when soil test levels are at or above a sufficiency did not increase grain yield.