Irrigation method and row pattern effects on soybean grain yield and water use efficiency

Investigators: Amilcar Vargas, Drew Gholson, Himmy Lo, Gurbir Singh, Dave Spencer, and Jason Krutz

Date: 2022

Project Summary

Introduction

The majority of soybean in the Mississippi Delta are grown on heavy clay soils and irrigated with furrow irrigation systems. Water management practices are needed in Mississippi to increase irrigation water use efficiency (IWUE). Increasing IWUE will help to reduce the groundwater withdrawals from the Mississippi River Valley Alluvial Aquifer. The objective was to determine the effects of two irrigation methods and row patterns on soybean grain yield, grain quality, and IWUE in the Mississippi Delta.

Materials and Methods

This study was conducted at the Delta Research and Extension Center on a Sharkey clay soil. The soybean variety AG 43x0 was planted on May 12, at the seeding rate of 135,000 seeds acre-1. Soybean was planted in two-row patterns twin- and single-row spaced at 40 inches. Soybean in twin row treatments were plan ted with a Monosem NG Plus-4 8-row planter and single rows were planted with a John Deere

7300 6-row planter. Irrigation methods were overhead sprinkler and furrow irrigation (Figure 1). A rainfed control was also included. Field management operations such as tillage, weed, and pest control were conducted following Mississippi State University Extension Service recommendations. Irrigation decisions were based on soil moisture sensors readings. Three soil moisture sensors were installed at 6, 12, and 24 inches depth. Irrigation was triggered when the weighted average of the three soil moisture sensor readings reached -80 kPa. Sensors at 6 and 12 inches were assigned 0.25 weight value each and 0.50 for the 24 inches depth sensor. Data collected included soybean grain yield, grain quality analysis, and water amount used by each irrigation system. Soybean was harvested on September 26 with a plot combine. The plot combine was equipped with an H2 grain gauge and paired with a computer for data recording, such as test weight, harvest moisture, and weight. Soybean yield was adjusted to 13% moisture. Grain quality analysis was conducted to determine protein, and oil content. Statistical analysis was performed using the statistical analysis software, SAS v. 9.4. Analysis of variance was conducted using the GLIMMIX procedure. Mean separations were performed using Fisher’s protected LSD at ? = 0.05.

Results and Discussion

The total amount of water used to irrigate soybean from R1 to R6.5 growth stages for each method was 7 and 12 inches for sprinkler and furrow, respectively. Irrigation intervals for both sprinkler and furrow were 6.5 and 13 days, respectively. Soybean under sprinkler irrigation produced 3.4 buc acre-1 more soybeans per inch of irrigation water compared to furrow irrigation (Table 1). Soybean planted in a twin row pattern produced 0.4 bu acre-1 more per inch of irrigation water than single-row soybean. The highest test weight was achieved by soybean under sprinkler irrigation 53.5 lb bu-1. Protein and moisture content was not affected by irrigation or row pattern. Sprinkler irrigation could be an alternative to furrow irrigation in the Mississippi Delta to ensure the Mississippi River Valley Alluvial Aquifer sustainability. Irrigating soybean with a sprinkler irrigation system and trigger irrigation at -80 kPa will help to reduced the groundwater withdrawals from the Mississippi River Valley Aquifer

• Topic:
• Irrigation scheduling
• Irrigation