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© 2005 Plant Management Network.
Accepted for publication 9 August 2005. Published 16 September 2005.

Soft Red Winter Wheat Cultivar Response to Tillage in the Mid-Atlantic Coastal Plain

Wade E. Thomason, Assistant Professor, Department of Crop and Soil Environmental Sciences, Virginia Tech, Blacksburg 24061; Paul A. Davis, Extension Agent, Virginia Cooperative Extension, New Kent 23140; and Dan E. Brann, Professor Emeritus, Department of Crop and Soil Environmental Sciences, Virginia Tech, Blacksburg 24061

Corresponding author: Wade E. Thomason. wthomaso@vt.edu

Thomason, W. E., Davis, P. A., and Brann, D. E. 2005. Soft red winter wheat cultivar response to tillage in the Mid-Atlantic Coastal Plain. Online. Crop Management doi:10.1094/CM-2005-0916-01-RS.

Abstract

Current cropping systems in the Mid-Atlantic Coastal Plain utilize no-tillage seeding methods for corn and soybean, but no-tillage small grain acreage is also increasing in this region. The objectives of this research were to evaluate soft red winter wheat cultivars for grain yield, test weight, and lodging across three tillage systems in the Mid-Atlantic Coastal Plain. Five soft red winter wheat cultivars were grown under no-tillage, reduced tillage, and conventional tillage in the Coastal Plain of Virginia from 2002-2004. Grain yields for the site averaged 80, 60, and 71 bu/acre in 2002, 2003, and 2004, respectively. Grain yield and test weight was effected by tillage treatment only in 2002 when the lower yields and test weights under conventional tillage were likely due to a higher degree of lodging. There was no consistent influence of tillage treatment on any variety. High-yielding cultivars performed similarly under conventional, reduced, and no-tillage systems. Cultivar recommendations for the region should not be made separately on the basis of tillage system.

Introduction

Cropping systems in the Coastal Plain area of Virginia commonly incorporate no-tillage seeding techniques for corn (Zea mays L.) and soybean (Glycine max L.) production. However, tillage prior to planting wheat (Triticum aestivum L.) is still a common practice. The typical crop rotation in the region is wheat followed directly with double-crop soybean in year one and corn in year two, thus wheat typically follows corn in the crop rotation. Tillage is performed to facilitate preparation of a good seedbed and to incorporate residue from the previous corn crop. Incorporation of corn residue is important because while the pathogen that causes Fusarium head blight (Fig. 1) in small grains, Fusarium graminearum, does not typically damage corn, it overwinters in infected corn residue (20). When favorable weather conditions occur, the fungus produces spores that can infect the individual flowers of each spikelet on the head and cause poor seed fill and shrunken grains in all small grain crops.

Fig. 1. Fusarium head blight symptoms in wheat.

Producers who seek to take advantage of the labor and machinery savings possible with no-tillage small grain production are using seeders capable of producing uniform crop stand, even planting into large amounts of residue (Fig. 2). Genetic resistance and cultural controls are being developed that will likely reduce the severity of Fusarium head blight infection, making no-tillage small grain production in the Mid-Atlantic Coastal Plain more common.

Fig. 2. Early-season no-till wheat in corn residue.

Major differences in soil properties and water relations between conventional tillage and no-tillage crop production systems have been demonstrated (9,10,13,16). These changes occur due to the practice of leaving old crop residue on the surface and increasing soil organic matter and the action of soil organisms on the soil organic fraction (6,9,14). Improved water infiltration and soil water holding capacity and increased soil organic matter associated with long-term continuous no-tillage production are also influencing producers to switch to no-tillage small grains.

Nationwide No-Till Small Grain Results

Results from trials examining the effects of wheat cultivar by tillage interactions in other areas have been mixed. In the north-central Great Plains, Hall and Cholick (11) found a significant interaction of cultivar and tillage on grain yield. Yields were found to range from a 9.8% decrease to an 11.6% increase for different cultivars across environments. Recent results from trials conducted in North Dakota indicate that grain yield and quality of five cultivars were unaffected by tillage system (2). Evaluation of 10 cultivars under conventional tillage, mulch tillage, and no-tillage conducted in Oklahoma demonstrated no interaction between cultivar and tillage system for grain yield leading the authors to conclude that development of cultivars specifically for no-tillage production was unnecessary (5).

Results from the Mid-Atlantic and Eastern U.S.

Results from trials in the Piedmont and Coastal Plain regions of North Carolina showed no difference in cultivar grain yield due to tillage system (18). Winter growth and tillering was lower with no-tillage; however, the authors concluded that separate cultivar trials under no-tillage and conventional tillage were unnecessary (18). Lower tiller production under no-tillage conditions has also been found to exist in spring wheat (3).

Limited research has addressed soft red winter wheat cultivar and tillage interactions in the Mid-Atlantic region and anecdotal reports from growers have indicated that some common cultivars may perform differently under different tillage systems. The objectives of this research were to evaluate soft red winter wheat cultivars for grain yield, test weight, and lodging across three tillage systems in the Mid-Atlantic Coastal Plain.

Field Trials

Five soft red winter wheat cultivars were grown under no-tillage, reduced tillage, and conventional tillage in the Coastal Plain region of Virginia in New Kent County from 2002-2004. Soil type was a Pamunkey fine sandy loam, (fine-loamy, mixed, semiactive, thermic Ultic Hapludalf). The cultivars planted were chosen to represent popular or promising cultivars in the Mid-Atlantic region (Table 1). All cultivars were developed by the Virginia Tech small grain breeding program, and were from different crosses except ‘Sisson’ and ‘SS 550.’ These two cultivars differ in maturity; ‘Sisson’ is early heading, while ‘SS 550’ is medium to late heading.

Table 1. Tested cultivar name, source, and traits, 2002-2004.

E = Early heading compared to the mean heading date of all cultivars tested.

M = Medium heading compared to the mean heading date of all cultivars tested.

Experimental design was a randomized complete block in a split plot arrangement with tillage treatment as the main plots and cultivars as sub-plots. The experiment was replicated four times. Plots were initiated by performing tillage operations on areas selected within a field where continuous no-tillage was practiced. In all cases, the previous three years of cropping in this experiment were wheat-doublecrop soybean (year 1) and corn (year 2), followed by the small grain experiment. Winter wheat following corn is the most common rotation in the region. In all years, after corn grain harvest, stalks were shredded with a rotary mower.

Each year, plots were moved to coincide with the crop rotation but were always located on the same soil type. Conventional tillage plots were moldboard plowed to a depth of 10 inches and disked to a depth of four inches prior to planting in the fall of 2001, which resulted in undesirable erosion. Thus in each of the subsequent years, tillage was limited to chiseling at a depth of 10 inches and double disking conventional tillage plots. Weed control and seedbed preparation for the reduced tillage plots was accomplished by disking to a depth of six inches twice prior to planting. No-tillage plots received a burn-down herbicide application of glyphosate at 0.40 lb a.i./acre at least one week prior to planting and were seeded directly into mowed corn stubble (Figs. 3 and 4). All plots were planted with a Hege 1000 plot drill in seven inch rows. Information on planting dates and cultural practices is listed in Table 2.

Fig. 3. Planting the no-tillage plots.		Fig. 4. The plot area immediately after seeding.

Table 2. Cultural practices, 2002-2004.

Herbicides and insecticides were applied as necessary to control pests. Plots were rated for lodging each year prior to harvest using the Belgian lodging index (15). Grain harvest was performed using a Massey Ferguson 8XP plot combine and plot weights measured using a Graingage stystem with the HM-400 HarvestData system (Juniper Systems, Inc., Logan, UT). A subsample was taken from each plot upon which test weight and moisture were determined using a GAC2000 grain sampler (DICKEY-john Corporation, Auburn, IL). Grain yields are reported on a 13.5% moisture basis. Statistical analysis was performed using the GLM procedure available from SAS (SAS Institute, Inc., Cary, NC). Due to interaction effects of treatments across years, each year was analyzed and presented separately. Mean comparisons using a protected LSD test were made to separate tillage treatments and cultivars where F-tests indicated that significant differences existed (P < 0.05). Listing of a product by brand name does not imply its endorsement by the authors or Virginia Tech.

Yield, Test Weight, and Lodging Effects

2002. Lodging was significantly different for tillage systems and between cultivars in 2002 (Table 3). Lodging was much more severe in the conventionally-tilled treatments than in either no-till or reduced tillage (Table 4a). The mean lodging index score for conventional tillage was 7.1 while scores for no-till and reduced tillage were 4.0 or below. An application of biosolids at 3.5 ton/acre (plant-available nitrogen at 160 lb/acre) was made to the entire experimental area in February of 2000 prior to corn planting. Residual soil nitrogen levels were not measured but more severe lodging in conventional tillage was attributed to greater N mineralization from the biosolids and thus plant available N in the tilled plots. Increased N mineralization rates of manure in tilled versus no-till production systems has been consistently documented and would likely be similar for biosolids (12). Cultivar also had a major impact on lodging, with ‘SS 520,’ showing the least lodging (Table 4b).

Table 3. Analysis of variance for lodging, test weight, and grain yield,
2002-2004.

 *,** Significant at the 0.05 and 0.01 probability levels, respectively.

Table 4a. Mean lodging index by tillage treatment,
2002.

Table 4b. Mean lodging index by cultivar, 2002.

† Belgian Lodging Scale = Area × Intensity × 0.2;
where Area = 1 to 10 with 1 being unaffected and
10 being entire plot affected, and Intensity = 1 to
5 with 1 being standing upright and 5 being totally
flat.

Cultivar by tillage interactions were found for both grain yield and test weight in 2002. It is interesting to note that four of the top yielding cultivar by tillage combinations include the cultivars ‘Sisson’ and ‘Southern States 550’ (Table 4c) which are both considered high yielding types under no-till conditions (1).

Table 4c. Mean grain yield and test weight affected by cultivar and tillage, 2002.

Test weights in 2002 ranged from a high of 58.8 to a low of 52.8 lb/bu with the lower limit of acceptability for flour milling purposes set at 56 lb/bu (Table 4c). As evidenced by the greater range in test weights, cultivar likely has the most effect on test weight when evaluated under the same environmental conditions. Test weight was significantly affected by cultivar in every year of this study (Table 3).

2003. No lodging occurred in any treatment in 2003. This seems to support the hypothesis that higher levels of residual N under conventional tillage in 2002 were responsible for the increased lodging. Tillage had no effect on yield or test weight in 2003 (Table 3). However, cultivar influenced both factors. Grain yields were highest with ‘Tribute,’ ‘Sisson,’ and ‘SS 550’ at 65, 63, and 61 bu/acre, respectively (Table 5). Mean yield for the trial was 19 bu/acre lower than in 2002 and was reflective of the wet and cold fall experienced by this crop. Among the highest yielding cultivars, only ‘Tribute’ also had superior test weight. Mean test weight for three cultivars, ‘Tribute,’ ‘McCormick,’ and ‘Sisson’ were above the critical value of 56 lb/bu (Table 5). Mean test weight for the trial was 55.9 lb/bu and was limited by multiple rains after grain maturity and late harvest.

Table 5. Mean grain yield and test weight by cultivar, 2003.

2004. Similar to 2003, no lodging was noted in 2004. Grain yield and test weight were influenced only by cultivar. This concurs with the results of Weisz and Bowman (18) and Cox and Shelton (4) who state that cultivars performed similarly across tillage systems. Due to favorable growing conditions including low disease pressure, only ‘Sisson’ produced yields that were significantly lower than the highest yielding cultivar and the entire trial averaged slightly more than 71 bu/acre (Table 6). The cultivars ‘McCormick,’ ‘Tribute,’ and ‘SS 520’ all produced grain yields in excess of 72 bu/acre. The trial mean yield in 2004 was not reflective of the excellent winter and spring growing conditions experienced by the crop. Dry weather in April and the warmest May ever recorded in Virginia combined to reduce expected grain yield and test weight in 2004. Test weights for ‘McCormick’ and ‘Tribute’ (50.3 and 50.8 lb/bu, respectively) were significantly higher than those for ‘SS 550’ and ‘Sisson.’ Mean test weight across all cultivars in 2004 was 49.6 lb/bu, which is extremely poor (Table 6). These low tests weights are reflective of the less than ideal environmental conditions during grain fill, late season rains, and late harvest.

Table 6. Mean grain yield and test weight by cultivar, 2004.

Conclusions

Lodging was experienced in only one season and was much more severe in conventional tillage compared with no-till or reduced tillage. Lodging was likely due to excess available N from biosolids applied the previous year. This is not unexpected as excessive N application, without addition of a growth regulator, often causes lodging in high yielding wheat (17,19). Conversely, N rate recommendations for no-till wheat are often increased by 10% over recommendations for conventional tillage to encourage tillering and overcome N immobilization that occurs as soil microbes break down residue. Nitrogen applications in the other years did not encourage lodging regardless of tillage treatment. Lodging that occurred in the conventional tillage treatments in 2002 was not a direct effect of tillage but more an effect of greater N mineralization in the conventional tillage treatments.

Across three years of testing, the lack of effect of tillage and the lack of consistent tillage by cultivar interactions indicates that there was no evidence to recommend specific varieties adapted to different tillage systems. Grain yields were affected by tillage only in 2002, likely due to the degree of lodging and the associated mechanical harvest difficulty in the conventional versus no-till plots. Grain yield and test weight have both been reported to decrease with increased lodging (10). There was a significant tillage by cultivar interaction effect in 2002; however the degree of lodging likely contributed to this. The lower test weights in 2002 are also associated with greater lodging. Test weight was unaffected by tillage treatment in either 2003 or 2004.

Yields in 2002 and 2004 were much higher than in 2003. In 2003 a wet, cold fall limited spring tillering, and potential yields. While these cultivars are all popular and widely grown within the region, they differ in time to spring green-up and heading date. Grain yield in the region is highly influenced by temperatures and rainfall just after anthesis and the reason that cultivar performance (rank) differed over years is probably due to a more or less favorable environment at this crucial period in the different years. Overall, grain yield, lodging, and test weight were not consistently affected by tillage treatment.

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