Weather conditions in the southwestern U.S. are variable and influence crop growing periods with late spring and early fall frosts which significantly impact cropping seasons. With the development of new maize hybrids, grain yield, evapotranspiration, and water use efficiency can be substantially impacted by planting density and planting date. Thus, it is critical that the optimum plant density and planting date for maximum grain yield be determined for local conditions. Field experiments were conducted to evaluate six plant densities (54700, 64600, 74600, 88000, 101700 and 120100 pph) under seven planting dates (from April 23 to June 5 in 2019 and from April 21 to June 10 in 2020) to determine the planting window and the optimum density. Plots were sprinkler irrigated and crop management was similar across all planting dates during the two growing seasons. The results showed that crop height and leaf area index varied with plant density and planting date. Grain yield also varied with plant density and planting date. The highest grain yield (16.8 Mg ha^-1) was observed under the density 101,700 pph and the first planting trended to provide the best grain yield in 2019. In 2020, the highest grain yield (17.77 Mg ha^-1) was obtained under the density 88,000 pph and the May 18 planting provided the best grain yield and the greatest WUE. Plant density 88,000 plant /ha was revealed the optimum density that maximized grain yield and WUE and maize planting after May 25 is not recommended.

Planting dates can have a significant impact on corn yields. In some cases, a higher seeding rate could help negate some of the negative impacts of a later planting date on yield. To compare the interrelationship of seeding rate to planting date to corn yield, this one-year study in Tifton, GA included four seeding rates of 24,000, 32,000, 40,000 and 48,000 seeds per acre in a Randomized Complete Block Design across three spring planting dates of March 15, March 31, and April 12 (n=48). Final grain yield and yield components were determined, including kernels per row, kernel rows per ear, ear length, and 100-seed weight. The greatest grain yield was found in the March 31 planting date, while across the planting dates 24,000 seeds per acre consistently yielded less than the 32,000, 40,000, and 48,000 seeds per acre. Results of this one-year study indicate that as planting date is delayed from mid-March to mid-April, an increase in seeding rate from 32,000 to 48,000 seeds per acre is necessary to stabilize yield. Complete results will be presented at the 2024 ASA Southern Branch Meeting.

Tropical Spiderwort (Commelina benghalensis L.), a federally designated noxious weed since 1983, has become a severe threat to Southeastern peanut production. First discovered in Florida, spiderwort has spread across to neighboring southern states. The ability to overtake and outcompete cash crops makes spiderwort a very aggressive and problematic pest. Only to add to the difficult management of tropical spiderwort, research conducted has shown a concerning abundance of herbicide resistance within this species. A statewide tropical spiderwort survey in Alabama followed by an herbicide resistance screening for five commonly used peanut herbicides was conducted to document its current abundance and herbicide resistance status. Plants of 20 Tropical spiderwort populations were grown from sandpaper-scarified seeds at the Auburn University greenhouse facilities under standard temperatures and normal daylight conditions germinated from scarified seeds collected from southern Alabama and Georgia. The recommended field rates of the herbicides were applied at the recommended growth stages. Results will be presented at the meeting.

Cotton (Gossypium hirsutum L.) is an important cash crop in the United States, grown mainly for fiber production, and plays a significant role in the feed and oil industries. Therefore, increasing cotton lint yields for food security and agricultural sustainability is an important objective for cotton breeders. Over the years, breeding practices have significantly improved cotton yield by considering aboveground growth only. However, there is minimal information available regarding how root structure has changed during the breeding process. Therefore, a field study was conducted at EV Smith (EVS) Research Center, Alabama, in 2020 and 2021 to understand how breeding and management practices have indirectly influenced the root distribution and architecture of cotton cultivars. A randomized complete block design (RCBD) with four replications was employed to study 20 cotton cultivars released over the past 70 years. The Shovelomics method was utilized to collect root crown samples at the peak flowering stage, which were subsequently phenotyped using the innovative RhizoVision Crown platform. Additionally, the Giddings machine was employed to excavate root samples at different soil depths, and the cleaned roots were scanned using a WinRhizo desktop scanner to calculate various root parameters. Early results indicate that newer cultivar produces shallow but complex root systems. More research findings will be added here.

Low forage yields from old alfalfa stands are often a result of poor management practices. Appropriate agronomic amendments such as potassium (K) fertilization and harvest time can help revive the yielding potentials of old alfalfa stands. A study was conducted on a 13-yr old alfalfa stand at UW SAREC, Lingle in 2019 to determine K × harvest time interaction effect on yield response of old alfalfa stands. Six K rates (0, 56, 112, 168, 224, and 280 kg K₂O ha^-1) were applied to alfalfa. Alfalfa was harvested at two harvest times (early harvest, late bud to early [10%] bloom; late harvest, 7 days after early harvest). Treatments were organized in a randomized complete block design with four replications. The 224 kg K₂O ha^-1produced the highest total forage yield (8.0 Mg ha^-1) at early harvest, while 168 kg K₂O ha^-1produced the highest total forage yield (8.6 Mg ha^-1) at late harvest. Differences in plant growth at both harvest times might have influenced the amount of K required to improve yield. There was a quadratic relationship (P= 0.01, R²= 0.39) between forage yield and relative water content of alfalfa. This suggests that the moisture content in alfalfa in conjunction with K and harvest management plays an important role in alfalfa for yield potential. Overall, preliminary results of the study indicate that applying K to old stands of alfalfa based on when to harvest could be a viable option to improve forage production of declining old alfalfa stands.

Potato is an important crop in Florida, with the northeast being a major production hub. The shallow root system of potato plants and the sandy soil conditions in this region makes most of the phosphorus (P) unavailable to the crop. However, overuse of P fertilizer can pollute nearby waterbodies through surface runoff and contaminant groundwater, along with reducing profit margin. To curb these problems, an alternative and eco-friendly solution is to integrate microbial consortium inoculation in nutrient management plans. This approach entails the introduction of a mixture of beneficial microorganisms into the soil to improve phosphorous use efficiency and plant growth. This approach can reduce the need for P fertilizers, thus protecting the environment. This study consisted of a commercially available biostimulant, a product containing friendly microorganisms like phosphorous solubilizing bacteria, which was applied along with variable P rates. This study aims to provide insights into the efficacy of using biostimulant as a strategy for enhancing potato crop productivity and sustainability. The study design used a split plot arrangement with four replications, where P rates defined main plot and biostimulant levels were adopted as sub-plots. We hypothesize that the integration of the biostimulant will enhance tuber yield and quality of potatoes with lower P dose. The findings of this study have the potential to contribute to the development of more sustainable and eco-friendly nutrient management plans for potato production.

Over the past few years peanut fields in parts of North Florida have shown moderate to severe symptoms of peanut decline late in the season. Many soils and plant nutrient, nematode, and disease diagnostic tests have been completed without reaching a conclusion. Many plant tissue test results have shown low potassium levels early in the season and continued to decrease on tests as the season progressed. Potassium is an essential nutrient for peanut health and is needed for many basic plant functions such as protein synthesis and pod development. Peanuts with potassium deficiencies show overall stunting, marginal leaf chlorosis, and poorly developed root systems. The appropriate dose of potassium to be applied to the soil may be affected by climatic conditions, genotype and the crop production and/or rotation system adopted. In the Suwannee Valley region with its sandy soil type, leaching of nutrients is a major problem especially when applied at the beginning of planting or when split applied (at planting and at bloom) which is the common practice followed by most farmers. Potassium, being highly leachable, is not available to peanuts in the later stages of its life cycle if applied at planting due to heavy/excessive rainfall events common in Florida. Controlled Release Fertilizer (CRF) releases small amounts of fertilizer components over time when the plant needs it. These polymer-coated fertilizers are designed to release nutrients at a predetermined rate over a specific time period. The release rate is aligned with the plant growth curve for specific crops and the release is guided by temperature for the region where the CRF will be used. This results in decreased nutrient losses and enhanced nutrient-use efficiency and use of controlled release potassium was investigated for peanut yield and grade.

Farm applied nitrogen (N) is one of the major contributors for nitrate-impaired water bodies in North Florida. To meet the Total Maximum Daily Load (TMDL) for nitrate in FL water basins, adoption of various Best Management Practices (BMPs) as part of Basin Management Action Plan (BMAP) are currently being assessed in Florida. Incorporation of pastures such as bahiagrass and cattle grazing on bahiagrass and on winter cover crops has shown to improve soil properties of the row crop land and tremendously improve the root properties of the row crops. To compare the efficacy of different cropping systems on water quality and nitrate fate in sandy soils of Northcentral FL, a 70-acre parcel of land was taken out of timber and established into a 16-year rotational production system under a 40-acre pivot system at North Florida Research and Education Center-Suwannee Valley, Live Oak, FL in 2018. A 10-acre quarter under the pivot serves as a cropping system. The four cropping systems include two-year rotations of corn (Zea mays)-peanut (Arachis hypogaea) and corn-carrot (Daucus carota)-peanut and four-year rotations of bahiagrass -bahiagrass-corn-peanut, and bahiagrass-bahiagrass-corn-carrot-peanut. Water quality from these cropping systems is being assessed using drain gauge lysimeters. This study is divided into increments of 4 years with first four years managed under normal farming practices. After first four years of rotation, introduction of different BMPs such as cattle grazing, use of soil moisture probes for irrigation management, and banding of liquid N in corn are being implemented for the next four-year cycle. Along with the introduction of BMPs, an adjustment to the rotation system is introduced to maximize yield potential for cash crops.