Performing Department
North Mississippi Research & Extension Center
Non Technical Summary
Most crop production in the "hill section" of north Mississippi is non-irrigated and prone to inconstant yields due to the lack of adequate soil moisture during critical stages of the growing season. In 2017, an estimated 2.25 million acres of soybeans were planted in Mississippi with a farm gate value of over 1.1 billion dollars (MSU-DAFVM 2017), which is 3rd in value only behind forestry and poultry. An estimated 42% of these acres were planted in a dryland environment (Heatherly 2017) that are prone to yields that are typically more than 15 bu/ac lower than irrigated soybeans (USDA-NASS 2012). Although dryland soybeans have a lower yield potential, they will remain an important production practice in Mississippi and across the United States because irrigation is not feasible due to technical and financial limitations in some areas (Popp et al., 2002). For example, the depth of an irrigation well could be 45 feet below land surface in the Delta of Mississippi compared to 675 feet in the "hill section" (USDOI-USGS 2018). Therefore, an alternative to irrigation is to focus on development of sustainable dryland systems to achieve more consistent crop yields. Identifying affordable cover cropping systems coupled with early planting in a no-tillage environment to minimize inconsistent yields due to lack of timely rainfall events could provide more than $40 million across the state of Mississippi in dryland soybean production based on a 10% increase in yield. Another challenge in crop production is weed management. Research indicates that corn and soybean yields could be reduced by 50% if weeds are left uncontrolled (Soltani et al., 2016, 2017). In the United States and Canada, this would be an estimated $43 billion loss in revenue just for these two crops. There are many herbicides labelled for use in major row crops, but only a hand-full are registered in specialty crops such as sweetpotato and sesame. There is a need for tolerance studies in specialty crops to identify potential herbicides that could be utilized for weed management. This will also require applied research to determine the appropriate use rate, tank-mix partner, and application time for specific herbicides in order to establish guidelines for the federal registration process. Sustainable and efficient crop production will be even more important for future generations and management of soil nutrients will play a vital role in achieving this task. Nutrient management would not be possible without soil test correlation and calibration research to provide the information necessary for interpretation and support of recommended fertilizer inputs (SERA-IEG-6 2014). The majority of soil test correlation and calibration studies in the southern states were conducted at state agricultural experiment stations between the 1950s through the late 70s (Jones 1979). Data collected from this early research serves as the basis for current fertilizer recommendations in reports from soil testing laboratories. Currently, most private laboratories utilize the Mehlich-3 method as a soil test extractant, while the soil testing laboratory at Mississippi State University (MSU) uses the Lancaster method (Cox 2001). In the 1970s, Dr. James D. Lancaster, an agronomist with MSU developed the Lancaster extraction method, commonly referred to as the Mississippi method (Cox 2001). Producers and consultants have expressed concerns over different soil test based fertilizer recommendations between Mehlich-3 and Lancaster extracted samples. Research information that correlates Mehlich-3 extractable nutrients to sweetpotato yield is very limited. Also, it is unclear when the Lancaster soil test method for potassium or phosphorus was correlated with sweetpotato yield in Mississippi or when fertilizer recommendations were last updated. In addition, it is important to note that Dr. Lancaster utilized cotton in research to set soil test ranges and fertilization recommendations for the Lancaster method. Some states have verified their calibration research over time, but new soil fertility research is limited, especially for sweetpotato. This suggests that soil testing practices should be reviewed and validated with calibration field plots. The use of auxin technologies in row crop production was launched in 2017 and the use of auxin herbicides in genetically enhanced tolerant crops is expected to increase over the next several years, which will increase the risk of injury to non-tolerant crops such as sweetpotato. Identifying the potential level of sweetpotato plant injury and yield reduction associated with the interception of off-target auxin herbicide movement during different stages of plant development will help the in-season, decision-making process to replant or take the crop to yield. Also, sweetpotato varieties may differ in their tolerance to abiotic stress linked to exposure to synthetic auxins and other herbicides. Understanding the level of injury expected with off-target exposure, coupled with the discovery of less susceptible varieties will help manage and mitigate risk to sweetpotato as it relates to the current landscape of evolving technologies.
Animal Health Component
50%
Research Effort Categories
Basic
25%
Applied
50%
Developmental
25%
Goals / Objectives
Evaluate sustainable cover crop systems for dry-land crop production. Crops are prone to inconsistent yields due to inadequate rainfall at the appropriate crop development stage. Therefore, a systems approach will evaluate the use of cover-crops, source of fertilizer, and crop planting date in a no-tillage environment to help improve soil health and provide more stable soil conditions for crop production.Determine weed control strategies to manage problematic weed species and mitigate herbicide resistant weed bio-types. Major row-crop production continues to advance with new crop resistant herbicide systems. However, herbicide registration for weed management in specialty crops such as sweetpotato is limited and they are not typically included in herbicide resistant crop breeding programs. Therefore, herbicide systems will be evaluated that include PRE-plant, Delayed-PRE, POST, and POST-directed applications in order to maximize control of problematic weed species and minimize risk of crop injury.Determine the optimum amount of phosphorous and potassium for sweetpotato production in using both Lancaster and Mehlich-3 extraction methods. Some states have verified their calibration research over time, but new soil fertility research is limited, especially for sweetpotato. Therefore, this project will investigate fertilizer inputs for sweetpotato with calibration field studies.Investigate off-target movement of auxin herbicides to specialty crops such as sweetpotato. Herbicide resistant crops have introduced a new dimension of weed control to manage herbicide resistant weeds in row-crop production systems. But it has also created the risk of injury to specialty crops planted due to volatility, drift, and tank contamination of auxin herbicides. Therefore, studies will be designed to simulate off-target movement of auxin herbicides to sweetpotato at different growth stages.
Project Methods
Objective 1. Studies will be conducted at the Pontotoc Ridge-Flatwoods Experiment Station in Mississippi to evaluate the effects that different cover cropping systems have on soybean growth/development and yield. Also, the effects on "soil health" (physical and chemical characteristics, microorganisms, soil moisture, and other parameters) will be evaluated. Site selection will be confined to dryland soybean production fields. Standard agronomic practices for soybean production in the area will be applied. Treatments will include 4 cover crops, 3 fertilizer treatments, and 3 soybean planting times. Baseline soil samples will be taken at the beginning of the project. A standard commercial fertilizer rate based on soil test recommendations will be made from the baseline soil samples. A nutrient analysis will be utilized to determine poultry litter application rates that coincide with the amount of K applied in the standard commercial fertilizer treatments. Experiments will be split-split plot arrangement replicated in a randomized block design. In addition to simple ANOVA and means separation, we will utilize SAS software for computations of correlation and regression analyses that best describe results (other methods will be employed if warranted).Objective 2. Herbicide systems will be evaluated for specialty crops such as sweetpotato. Treatments will include PRE-plant, Delayed-PRE, POST, and POST-directed applications in order to maximize control of problematic weed species and minimize risk of crop injury. Some greenhouse studies will be included when appropriate, but most evaluations will be conducted as field studies. Treatments will be arranged in a randomized complete block design with at least 4 replications. All studies will utilize the Agronomic Research Management software to record observations, plant measurements, and to calculate statistical formulas. Data will be interpreted and prepared for the appropriate avenue of dissemination.Objective 3. Fertilizer studies will be conducted at the Pontotoc Ridge-Flatwoods Branch Experiment Station and at cooperator locations where commercial sweetpotato production occurs. Site selection will be based on soil that has a low to very-low soil test P and K nutrient level and of the same soil type typically used for sweetpotato production. Baseline soil samples will be collected from each plot and analyzed for available nutrients using both Mehlich-3 and Lancaster extraction methods. Treatments will include an unfertilized check and a range of K2O rates such as 60, 120, 180, 240, 300, and 360 lb/ac and P2O5 rates such as 40, 80, 120, 160, 200, and 240 lb/ac. All studies will be designed as a randomized complete block with 4 replications. Sweetpotato growth will be monitored during the growing season. The two center rows of each plot will be harvested with a chain-digger at 90 to 110 days after transplant. Sweetpotatoes will be graded and yield determined for US no. 1, canner, jumbo, culls, and total marketable grades. Statistical analyses will be conducted and interpreted to determine the target P and K level to optimize yield of US no 1 grade sweetpotato.Objective 4. Investigate off-target movement of auxin herbicides to specialty crops such as sweetpotato. Field studies conducted at the Pontotoc Ridge-Flatwoods Branch Experiment Station will include drift and tank contamination treatments with dicamba formulated with diglycoamine (DGA) salt and 2,4-D formulated with choline salt at rates such as 0x, 1/8x, 1/16x, 1/64x and 1/512x of the registered labeled rate at several application times such as Pre-transplant and 1, 3, 5, and 7 weeks after planting (WAP). The experiment design will be a randomized complete block with a minimum of four replications. Visual injury ratings will be recorded 1, 2, and 4 weeks after treatment applications on a scale of 0 to 100% (no injury to plant death) according to injury type (chlorosis, necrosis, stunting, epinasty). Data will be subjected to statistical analyses followed by interpretation of results to determine the extent of crop injury as it relates to plant exposure at a specific growth development stage and herbicide dose.