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© 2006 Plant Management Network.
Accepted for publication 1 January 2006. Published 28 February 2006.

Peanut Response to Conservation Tillage Systems

W. James Grichar, 3507 Hwy 59E, Texas Agricultural Experiment Station, Texas A&M University, Beeville 78102

Corresponding author: W. James Grichar. w-grichar@tamu.edu

Grichar, W. J. 2006. Peanut response to conservation tillage systems. Online. Crop Management doi:10.1094/CM-2006-0228-01-RS.

Abstract

Field studies were conducted during the 2003 and 2004 growing seasons in the south Texas peanut-growing area to compare yield and quality of peanut (Arachis hypogaea L.) among three conservation tillage systems (strip-till, reduced-till, and terra-till) and a conventional tillage system. The strip-tillage system produced the lowest peanut yields and net returns in both years of the study, while the terra-till system produced yields and net returns comparable to the conventional tillage system. Since the soils at this location were high in sand content (> 70%), compaction was not a problem. However, in 2003, digging of the strip-tillage plot was a problem. Peanuts in the strip-tillage system were planted flat compared with the other systems and the blades of the peanut digger were not able to penetrate far enough into the ground to dig all the peanut pods. Therefore, many pods were pulled off the vine or left in the soil during the digging operation. In 2004, the blades of the peanut digger were adjusted to reduce this problem but peanut yield in this system was still low.

Introduction

Soil erosion, declining soil productivity, and surface water quality have become major concerns in recent years and have created interest in conservation tillage (17). The 1985 Farm Bill (4) stimulated additional interest in sustainable agriculture by mandating conservation compliance and specified that measures to reduce soil erosion should be initiated by 1990 and fully implemented by 1995. Cost effective soil- and water-conserving tillage systems are an essential component of sustainable agriculture. Johnson et al. (10) reported crop residues left on the soil surface essentially eliminated erosion problems. Musick et al. (13) found that an irrigated wheat (Triticum aestivum L.) mulch increased soil water storage by 2.5 inch in an 11-month fallow period. The extra soil water increased subsequent grain sorghum yield by approximately 980 lb/acre. These reduced-tillage systems can also result in considerable savings in energy, machinery, and labor requirements (5). The use of reduced- and strip-tillage production systems have reduced production costs in several crops including corn (Zea mays L.), cotton (Gossypium hirsutum L.), grain sorghum [Sorghum bicolor (L.) Moench], and soybean [Glycine max (L.) Merr.] (12,14,17,19). While some research has been published on peanut production under reduced tillage (5,6,7,8,10,11,16,20), peanut growers have been reluctant to adopt these systems.

Many peanut growers feel that a well-prepared seedbed is essential for a good peanut crop (9). This may be due to a perceived need for burial of crop residues to reduce the possibility of disease problems. Recent studies in the southeast have shown that the incidence of spotted wilt disease (Tomato spotted wilt topovirus) in peanut is significantly less in conservation tillage than in conventional tillage (11). Growers have also been reluctant to adopt reduced tillage systems due to perceptions that they lead to poor weed control. Recent research in several crops grown using reduced-tillage systems has shown that effective weed control is possible in this type system (11), adding further incentive for growers to alter their peanut production strategies.

Peanut growers are also concerned that reduced tillage systems will lead to lower yield and poor quality. While studies in the southwestern US have shown yield reductions with no-tillage systems (5,6,7,8); several studies conducted in the southeastern United States have identified conservation tillage production practices that have produced peanut yields equivalent to those measured under conventional tillage (2,3).

Over the past few years, the number of growers in the U.S. using conservation tillage practices in peanut production have increased (15). This increase in conservation tillage is due primarily to time and labor savings during the spring (10). Conventional tillage requires multiple tillage operations in rapid succession, which can be complicated by weather delays and shortages in skilled agricultural labor. Conservation tillage either eliminates tillage operations or reschedules tasks easing logistical complications (10).

With the increased interest in conservation tillage systems in Texas, field studies were conducted in 2003 and 2004 to compare several different conservation tillage production systems with the conventional production system for peanut yield, grade, and net returns. Using standard disease control practices, foliar and soil-borne diseases were also evaluated to compare the various systems.

Field Trials Using Several Tillage Systems

Field studies were conducted during the 2003 and 2004 growing seasons on a producers field near Pleasanton, TX. Soil at this location was a Wilco loamy fine sand (fine, mixed, hyperthermic Udic Paleustalfs) with 1% organic matter and pH 6.8 to 7.2. The study site was watered with supplemental irrigation. In 2003, supplemental irrigation was needed during the early portion of the growing season but rains were prevalent from July to harvest in October; while in 2004 above-normal rainfall was prevalent throughout the growing season and irrigation was not required. The experimental design was a randomized complete block with four replications. Plots consisted of twelve rows, 300 feet long, spaced on 38-inch centers.

The experimental area in each year was seeded with wheat ( Triticum aestivum L.) in the fall prior to spring peanut planting. The experiment consisted of four treatments. Three different conservation tillage systems including strip-tillage, terra-tillage, and reduced-tillage were compared with conventional tillage (Table 1). In the conservation tillage plots, the small grain stubble was shredded approximately 12 inches tall after the grain was harvested. Approximately two weeks after small grain harvest, glyphosate (1 qt/acre) was broadcast-applied to kill the small grain cover crop and any existing weeds. Within 7 to 10 days of glyphosate application, the conservation tillage equipment was used and peanuts were planted.

Table 1. Tillage systems used in study and costs involved.

 ^x Number of trips through field.

Under the conventional tillage system, after the cover crop was shredded, an offset disc was used over the area two times to break up plant tissue and root system of the wheat, soil was turned with a moldboard plow, then disced to break up large clods, and bedded with disc bedders. The beds were leveled to planting height, peanuts planted, and the preemergence (PRE) herbicide applied.

Under the terra-tillage system, after the cover crop was shredded, an offset disc was run over the area two times, the terra-till unit ( Bingham Bros., Lubbock, TX 79403) was used to prepare an area for planting, peanuts planted, and the PRE herbicide applied. The terra-till unit consisted of a subsoil shank which penetrated the soil to a depth of approximately 36 inches with twin sets of bedder sweeps mounted on either side of these shanks which prepared a small bed approximately 3 to 4 inches tall.

Under the reduced-tillage system, after the wheat crop was shredded, an offset disc was used over the test area two times, land was bedded with disc-bedders, beds leveled during the planting operation, peanuts planted, and the PRE herbicide applied.

Under the strip-tillage system, after the wheat crop was shredded, seedbeds were prepared with a Bush-Hog Ro-Till (Bush-Hog, Inc., Selma, AL) unit which tilled a 14- to 16-inch wide planting strip on 38 -inch centers. The Ro-Till unit consisted of a subsoil shank which penetrated the soil to a depth of approximately 16 inches while twin sets of fluted coulters were mounted on either side of these shanks. The subsoiler shanks opened the soil and destroyed any plow-pan beneath the row. The fluted coulters smoothed the soil and broke up any large clods. Rolling crumblers mounted immediately behind the flutted coulters further smoothed and shaped the seedbed. The PRE herbicide was applied and peanuts planted.

Pendimethalin (Prowl; BASF Corp., Research Triangle Park, NC) was selected as the peemerge herbicide because many peanut growers in the southwestern U.S. are using it in their peanut herbicide program (author’s personal observation). Pendimethalin at 1 qt/acre was applied immediately after peanuts were planted. Pendimethalin is a member of the dinitroaniline group of herbicides, and these are the only-soil applied herbicides registered for peanut which control Texas panicum adequately all season (20). Imazapic (Cadre; BASF Corp.) was applied postemergence (POST) to control any broadleaf weeds and yellow nutsedge (Cyperus esculentus L.) while clethodim (Select; Valent USA Corp., Walnut Creek, CA) was applied POST to control any annual grass escapes.

‘Tamrun-96’ peanut was planted in 2003 and ‘OL 01’ was planted in 2004. Peanuts were planted with a Monosem precision planter (Monosem ATI, Inc., Lenexa, KS) at the rate of 90 lbs/acre in all tillage systems. The planting date in both years was June 12. Crop and disease management practices were held constant over the experiment and were based on Texas Cooperative Extension recommendations.

Foliar and soil-borne disease observations were made during the growing season and immediately after peanuts were dug. Since disease levels were low throughout the season only visual ratings were made.

Peanuts were dug when 135 to 140 days old and allowed to remain on the soil surface for 7 to 10 days to air-dry. Individual plots were then harvested with a combine. After combining, samples were dried to 10% moisture, foreign material was removed from samples, pod weights recorded, and percentage of peanut grade (sound mature kernels plus sound splits) determined for each plot. Dollar value per acre and deductions were determined based on Federal Loan Rate Schedule. Data were subjected to analysis of variance and means were separated using Fisher’s protected least significant difference test at the 0.05 probability level.

Tillage System Effects on Peanut Yield and Quality

Since there were no year by tillage system interactions, data were combined over the two years. Foliar and soil-borne diseases did not differ in any system (data not shown). The test area was sprayed for foliar diseases with chlorothalonil (Bravo; Syngenta, Greensboro, NC) and tebucanozole (Folicur; Bayer CropScience, Research Triangle Park, NC). As a result, very little leafspot was noted. Soil-borne diseases were not a problem in either year. Despite initial reports by Boswell and Grichar (1) that southern blight was a major problem in reduced-tillage systems, later work indicated no differences in southern blight disease development among tillage systems (5). Grichar and Smith (6,8) also reported that southern blight was not a major deterrent to reduced-tillage production of peanuts.

Table 2. Peanut response to reduced-tillage systems.

 ^x Grade = sound mature kernels (SMK) + sound splits (SS).

 ^y Deductions include $0.80 for each percent of sound splits over 4.

The conventional tillage system required six trips through the field and resulted in the highest land preparation costs while the strip-tillage system required the least number of trips and resulted in the lowest costs (Table 1). The conventional and terra-tilled systems produced the highest yield, gross dollar value and net dollar value per acre (Table 2). All systems except the strip-tillage system produced over 3000 lbs/acre. The lower yield with the strip-tillage system was due in part to peanuts left in the soil during the digging process especially in 2003 (data not shown). Due to a lack of raised bed with this tillage system, the blades on the peanut digger were not able to penetrate the soil deep enough to dig all the peanut pods and as a result many of the pods were left in the soil. Peanut grade was not affected by any tillage system indicating that peanuts matured equally under all production systems.

Other studies with peanut using reduced-tillage systems have produced mixed results. In early work, Varnell et al. (18) concluded that pod yield and quality were reduced under a no-till system. In comparison with conventional tillage practices, no-tilled production reduced foliage, pod, and kernel yields by 58, 64, and 62%, respectively. Soundara Rajan et al. (16) reported no reduction in yield as a result of no-till management. They found that sandy loam soil facilitated easy peg penetration and pod development and that higher soil moisture retention in no-tilled plots accounted for no yield reduction. Colvin and Brecke (2) found that reduced-tillage production did not affect peanut yield and that cultivars did not differ in response to tillage system. In other work Colvin et al. (3) determined that for maximum peanut growth and yield there was no substitute for a friable seedbed. They stated that plots that received some degree of surface tillage yielded better than plots with no surface preparation.

Conclusions of this Research

In the terra-till system the elimination of deep plowing with a moldboard plow not only reduced production costs and equipment wear-and-tear, but also resulted in a higher net return per acre. However, the use of a strip-tillage system without a slightly raised bed resulted in the lowest yield and net return. Results of this study generally agree with those of Colvin et al. (3) that a friable seedbed is needed for maximum peanut growth. Also, problems with digging peanuts in a strip-tillage production system were apparent and for this system to work additional adjustments in digging equipment would be required.

Observations on foliar and soil-borne diseases indicated no differences in disease development between tillage systems. However, disease levels were low for both foliar and soil-borne pathogens and the fungicides Bravo and Folicur were used to control both type pathogens. The increased organic matter present in the reduced tillage plots did not result in an increase in any pod diseases.

Pesticide usage, particularly herbicides, may be increased with any reduced tillage procedure. The additional herbicide costs in a reduced tillage peanut production system should be factored into any decision that a grower makes when deciding on the type of tillage system.

Acknowledgments

The National Peanut Board (NPB) as administered by the Texas Peanut Producers Board provided funds for this research project. Kevin Brewer, Dwayne Drozd, and Bill Klesel helped in plot maintenance and peanut harvest.

Literature Cited

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