Strip Tillage and Fertilizer Placement Effects on Irrigated and Dryland Corn Production

Investigators: Gurbir Singh, Chad Hankins, Gurpreet Kaur, Drew Gholson

Date: 2021

Project Summary

Introduction

Many farmers in the Delta perform most of their tillage operations in the fall both to save time in the spring and to create furrows for improved drainage during rainy winter months. Another reason for fall tillage in this region is that soil tends to be dryer during this time, which results in less resistance and draft on equipment (Raper et al., 2000) and less compaction than tillage on the normally moist soils in early spring (Tupper, 1974). No-tillage and reduced-tillage systems have not been widely adopted in this region due to poor natural drainage, high weed and disease pressure, and the need to remove equipment ruts after harvest (Blessitt, 2008). The overall objective of this study was to evaluate the effects of conservation tillage system (strip tillage) and conventional tillage systems (conventional tillage and sub-soiling) with fertilizer placement on corn stand establishment, grain yield and quality, and P and K uptake in continuous corn production. We hypothesized that among the strip-till treatments, the deep banded fertilizer placement treatment will have greater P and K agronomic efficiency due to greater P and K uptake in the crop biomass. The combination of strip tillage and deep banded fertilizer placement will prove cost-effective on larger farm operations (>1,000 ac), maintaining similar yields compared to sub-soiling or conventional tillage while saving in fuel and labor costs

Materials and Methods

In this project, we compared existing tillage systems—conventional tillage and conventional tillage with sub-soiling—to strip tillage for both irrigated and dryland corn. This study was established at the National Center for Alluvial Aquifer Research (NCAAR), Delta Research and Extension Center (DREC) at Stoneville, MS. A field with a history of continuous corn with low to medium soil phosphorus and potassium values was selected for this research. The soil series of the research field was Bosket very fine sandy loam. Conventional tillage operation involved two passes of disk followed by a pass of hipper and a pass of do-all bed preparation before planting. The sub-soiling involved a single pass of parabolic subsoiler in addition to all operations of conventional tillage. The strip tillage included a single pass operation with Orthman 1tripr strip-tiller which had a vertical tillage shank of 11 inches that tilled soil underneath the seedbed. We also evaluated phosphorus and potassium fertilizer placement in the split plots under three tillage systems. Fertilizer placements included broadcasting fertilizer and incorporating it with tillage, broadcasting fertilizer after tillage operation, and banding fertilizer with strip-till below the seedbed. The experimental design was a splitplot design with four replications planted under both irrigated and dryland conditions. All tillage and fertilizer placement treatments were carried out in fall after harvesting corn. Corn hybrid DKC 70-27 was planted in a twin-row pattern on 4/6/2020 and 3/10/2021 at a seeding rate of 38,000 and 40,500 seeds/ac, respectively. The fertilizer rates applied to corn were 232-50-100 lb/ac N-P2O5-K2O. Corn aboveground biomass was collected on 8/8/2020 and 8/11/2021 for determining corn silage yield and its phosphorus and potassium uptake. Due to the timely precipitation, irrigation was only applied three times over the whole growing season in both growing seasons of 2020 and 2021. Two center rows of each 4-row plot were harvested on 9/11/2020 and 8/27/2021 using a Kincaid 8xp plot combine. At the time of harvesting, grab samples were collected to determine grain moisture, bushel test weight, seed index (100- seed weight), and grain quality (protein, starch, and oil). Grain samples were also sent to a lab for a complete nutrient analysis for determining nutrient uptake. Soil samples were collected at two depths after harvesting in fall 2020, before planting in spring 2021, and after harvesting in fall 2021. These soil samples were sent to a lab for Mehlich- 3 extractable available nutrient analysis. Soil physical properties including compaction (bulk density and penetration resistance), electrical conductivity, volumetric water content were also determined before planting in spring 2021. All the data were analyzed using the univariate procedure in SAS (SAS Institute, Cary, NC) for determining the normality of the data, and wherever needed data was transformed to lognormal and transformed back to normal for reporting. The Glimmix procedure was used for analyzing the significance of the model. The dryland and irrigated studies were analyzed separately with tillage and placement as fixed effects and replications as the random effect. The placement of fertilizer was the split factor in the model. The model analysis was conducted at alpha = 0.05. The least-square differences among treatment means were analyzed using T-grouping in SAS at alpha = 0.05.

Results and Discussion Corn Grain Yield

Sub-soiling and strip tillage both increased corn grain yield by 18.5 and 13.7 bu/ac when compared to conventional tillage under irrigated conditions (Figure 1). Under dryland conditions, conventional tillage yielded 14.0 and 11.5 bu/ ac less compared to sub-soiling and strip tillage treatments, respectively. No significant differences were obtained between sub-soiling and striptill treatments for corn grain yield when pooled over fertilizer placement treatments. Similar corn grain yields among strip-till and sub-soiling treatments indicate that 1-pass operation of strip tillage can be economically beneficial to Mississippi growers and have the potential to replace sub-soiling with conventional tillage which is at least a 3 to 4 tillage passes operation.

Soil Fertility

In spring 2021 soil sampling, a three-way interaction between tillage, fertilizer placement, and depth was significant for Mehlich-3 extractable potassium (p-value < 0.05).Potassium fertilizer when deep banded (incorporated) with strip tillage at 8-inch depth retained the highest potassium in the soil at the depth of 6-12 inches suggesting that potassium nutrient losses were reduced when compared to other tillage by placement treatments (Figure 2). Under irrigated conditions for fall 2021, soil test P for strip-till incorporated treatment was 27.3 mg/kg and was at least double in P nutrient concentrations when compared to all other tillage by placement treatments (Figure 3). Similarly, strip-till incorporated soil test K was highest during fall 2021 soil sampling and was significantly different from all other tillage by placement treatments except strip-till broadcast (Figure 3). Overall, soil sampling results indicate that if the goal of the grower is to maintain and retain P and K fertilizer in the soil, a best management practice would be to incorporate the P and K fertilizer below the rooting depth. Over time bands of high fertility can be created in the field and precision planting on these high fertility bands can be accomplished using RTK planting systems.

References

Blessitt, J. (2008). Productivity of raised seedbeds for soybean [Glycine max.(L.) Merr.] production on clayey soils of the Mississippi Delta. Doctoral Dissertation, Mississippi State University.

Raper, R. L., Reeves, D. W., Burmester, C. H., & Schwab, E. B. (2000). Tillage depth, tillage timing, and cover crop effects on cotton yield, soil strength, and tillage energy requirements. Applied Engineering in Agriculture, 16(4), 379. Tupper, G. R. (1974). Design of the Stoneville parabolic subsoiler (MAFES Information Sheet 1249). Mississippi State University.

Project Photos

• Crop Type:
• Corn

• Topic:
• Soil
• Technologies
• Tillage