Project 1:
Understanding when and how much to irrigate soybeans in different soil types during variable rainfall conditions is important to Tennessee row crop producers. A field with extremely variable soils at the West Tennessee Research and Education Center (WTREC – Jackson, TN) was used for a small-plot soybean-irrigation experiment for the first time in 2018. The water holding capacity in this field ranges fro 07 to 2.2 inches per foot in the sandiest to the deepest silt loams, respectively. Rainfall at Jackson was higher than in many other parts of West Tennessee during the 2018 growing season with 16.3 inches of rain received between the R1 to R6 growth stages. At this high rainfall amount, yield response to irrigation was small in the deep silt loam soils, only around a 5% increase, while the best yield in the sandiest soils were more than doubled by starting irrigation at R3 at a rate of 1.64 inches per week totaling 6.6 inches of water applied. More detail on the results of this experiment can be found in the 2018 report to the TSPB.

Project 2:
The main goal of this study is to find out the optimal irrigation scheduling for soybeans using VRI system to be able to answer irrigation challenges which West TN producers are currently dealing with: should irrigation begin at first flowering (R1) or at pod initiation (R3)? Should irrigation be terminated when the seeds are full (R6)? Producers need specific recommendations on when to start and stop irrigating soybeans (while taking into account soil moisture) to optimize yield and maximize profit.

Project 1:
- Identify optimum irrigation in terms of initiation timing and application rate for soybeans in three soils: 1) deep silt loam, 2) silt loam over sand, and 3) loamy sand.
- Identify soybean irrigation trigger points for soil matric potential sensors in MOIST+.
- Identify soybean irrigation trigger points for the water balance scheduler in MOIST+.

Six irrigation treatments will be randomized and compared to a rain-fed control in 3 distinct soil types. The deep silt loam and silt over sand soils will be replicated 4 times while the sandiest soil will only have 3 replicates. Irrigation will be initiated at R1, R3 and R5 and within each timing two irrigation rates will be applied, 1.64 and 1.1 inch/week. Irrigation treatments will be adjusted for rainfall events and soil matric potential sensors will be installed to monitor soil water status.

Projct 2: This project is a continuation of work begun in 2014 and will specifically address these questions by continuing a large plot field trial to achieve the following objectives:
- Determine the latest effective growth stage to initiate irrigation to maximize yield.
- Determine the earliest effective growth stage to terminate irrigation to maximize yield.
- Determine how crop development, growth rate, and maturity are affected by timing of irrigation initiation and termination.

Research will be continued at the Milan REC under a center pivot irrigation system equipped with VRI technology. The trail will consist of 3 irrigation initiation stages (R1, R3, R5) X 1 irrigation termination stages (R6) X 1 maturity group (late IV) X 1 variety X 4 replications. All irrigation treatments will take into account natural rainfall and soil moisture will be monitored.
Also, soil samples will be collected separately from each plots after designing the filed and before assigning the treatment to make sure there is no huge differences in soil quality among the plots.