2001 Table of Contents

2001 STEEP III Progress Report

RESEARCH PROJECT TITLE:

Long-Term Alternative Crop Rotations Using No-Till in Low-Rainfall Dryland Areas: Years 4 through 6.

INVESTIGATORS:

William Schillinger (PI), WSU research agronomist, Lind
Ron Jirava, grower and cooperator, Adams county
R. James Cook, WSU plant pathologist and endowed wheat chair, Pullman
Harry Schafer, WSU agricultural research technician, Lind
Neil Christensen, OSU extension soil scientist, Corvallis
Doug Young, WSU agricultural economist, Pullman
Ann Kennedy, USDA-ARS soil microbiologist, Pullman
Bruce Sauer, WSU farm manager, Lind

DURATION:

Fifth of six years. This study is a continuation of a STEEP-funded project with the same title (years 1 through 3).

OBJECTIVES:

The objective of the study is to determine the long-term feasibility of diverse, cereal-based, no-till cropping systems for low-rainfall dryland areas of the inland Pacific Northwest. Specific objectives are to evaluate and compare several long-term no-till annual cropping systems on: (i) root disease, soil moisture dynamics, and grain yield of wheat, (ii) weed species shifts and weed ecology, (iii) physical and biological properties of the surface soil, and (iv) the agronomic and economic of potential as a replacement for the traditional winter wheat-summer fallow system.

KEY WORDS:

No-till, low-rainfall, alternative rotations, dryland

STATEMENT OF PROBLEM:

Farming in the dryland areas of the Pacific Northwest (less than 12 inch annual) has been mostly an intensive tillage-based wheat-fallow system since the land was broken out of native grassland and sage in the 1880s. Tillage is well known to accelerate the loss of soil organic matter by increasing biological oxidation and often by increasing soil erosion. The loss is exacerbated with fallow because oxidation of carbon exceeds carbon input from crop residues during the 2-year cycle. Because of the decline in organic matter and associated soil quality, most tillage-based farming systems in dryland environments are not sustainable in the long-term. Options for maintaining and improving soil quality in the drylands are to simultaneously increase the cropping intensity and reduce or eliminate tillage.

ZONE OF INTEREST:

The low-rainfall (6-to 12-inch annual) dryland area of east-central Washington and north-central Oregon. This zone encompasses 3.5 million cropland acres.

ABSTRACT OF RESEARCH FINDINGS:

The 2001 crop year was one of extreme drought that severely affected spring-sown crops in all low-rainfall dryland regions in the inland Pacific Northwest. Grain yield in continuous spring wheat plots was 14 bu/a in 2001 compared to the previous 4-year average of 44 bu/a. After consulting with a grower-scientist advisory committee, two new 4-year rotations were added to the study for years 2001-2004 (Table 1). Similar to spring-sown crops, re-crop winter wheat failed in the 2001 crop year. Winter wheat, grown after 4 years of continuous spring cropping where annual grass weeds were not present, was heavily infested with downy brome. Winter wheat seedlings survived the winter under 100+ days of snow cover only to die from Rhizoctonia root rot during the 2-3 leaf stage of growth in early spring. Rhizoctonia occurred in large patches. There are reports in the literature that Brassica spp. such as mustard and other deep-rooted broadleaf crops reduce disease pressure and enhance grain yield of the subsequent wheat crop. We have not found this to be true in this study. Considering that broadleaf crops provide no apparent benefit for Rhizoctonia root disease control and leave less soil water available for the ensuing one or two cereal crops, growers in low-precipitation areas on the inland PNW are probably better off to plant continuous cereals.

RESULTS AND INTERPRETATION:

Phase II Crop Rotations
The first four years of cropping systems research in Adams and Douglas county was completed in 2000. In January 2001, a meeting of growers and scientists was held to discuss the future of the Adams county experiment. The group decided to expand the experiment to include two 4-year rotations as well as two 2-year and two continuous rotations using soft white and hard white spring wheat and spring barley (Table 1). Both 4-year rotations contain winter wheat. Expansion of the project in phase II was possible because the original plots were 60 ft x 500 ft (total = 28 plots). Beginning in the 2001 crop year, we split each plot to create 30 ft x 500 ft strips (total = 56 plots). We were able to create the additional treatments and still have four replicates; thus the statistical precision of the experiment was maintained.

Table 1. Previous (1997-2000) and current (2001-2004) crop rotations in the long-term cropping systems study at the Ron Jirava farm in Adams County, Washington. All phases of each rotation are planted every year in 500-ft-long plots, each replicated four times.

Abbreviations: HWSW, hard white spring wheat; SB, spring barley; SWSW, soft white spring wheat; SWWW, soft white winter wheat; YM, yellow mustard.

Douglas County
Brad Wetli, grower cooperator at our cropping systems site in Douglas county from 1997 to 2000, chose to leave farming in 2001 to pursue other business interests. A meeting was held with Douglas county growers in February 2001 to discuss the future of the plots at the Wetli site. The consensus of the growers was to discontinue the cropping systems research because the grain yields of spring crops were not competitive with winter wheat-summer fallow. The Douglas county growers feel that they must plant their spring crops before late April-early May to achieve optimum yields, but this is difficult due to lingering snow cover and saturated surface soils. In leu of cropping systems research, the growers asked for research on dormant fall seeding of spring cereals that includes use of polymer coated seed. The PI is already involved in dormant seeding using polymers at Lind and agreed to extend this work to Douglas county beginning in November 2001. We did complete one cycle of a four-year crop rotation at the Wetli farm and data will be reported from that site in both popular publications and in referred journal articles.

Crop Yields
Grain yields for all years at the Adams county site are shown in Table 2. In 2001, grain yield for all crops was very low due to drought conditions. There was an average of only 2.25 inches of available soil water in the six-foot soil profile in mid-March 2001 and only 2.40 inches of rainfall occurred between March and August. Green patches of healthy spring wheat and barley were surrounded by vast areas of drought stressed wheat. These "leopard spots" occurred widely throughout the inland PNW wheat region in 2001 and are certainly associated with drought, but their exact cause remains a mystery. Numerous life-long growers reported that they had never previously seen such leopard spots in their fields.

Re-crop winter wheat grain yields were 7 bu/a or less in 2001 (Table 2). Many winter wheat seedlings survived the winter months only to be killed by Rhizoctonia root rot in early spring. There was heavy downy brome infestation in winter wheat grown after four years of continuous spring wheat during which time downy brome was completely absent. Downy brome infestation was not as bad in winter wheat grown after yellow mustard compared to after continuous spring wheat, but Rhizoctonia root rot appeared to be more severe (see Rhizoctonia section of this report). The best cereal yields (14 bu/a) were achieved in the continuous soft white spring wheat plots (table 2).

Table 2. Crop yields at the Ron Jirava farm in Adams county, Washington since beginning the cropping systems study in 1997. The 2001 crop year was a transition period where two new four-year rotations were introduced.

Also in 2001:
Winter wheat after 4 years of continuous spring wheat = 7 bu/a.
Winter wheat after back-to-back broadleafs (i.e., safflower and YM) = 5 bu/a.
Hard white spring wheat after barley = 10 bu/a.
Hard white spring wheat after back-to-back broadleafs = 6 bu/a.

Weeds
Weed dynamics in the various cropping systems have been carefully monitored. The major weeds at both Adams county and Douglas county sites during phase I were Russian thistle, mares tail, prickly lettuce, and tansy and tumble mustard. Appendix 1 shows the number and dry biomass of these weeds at both sites just before grain harvest averaged across years (1997-2000). Russian thistle was by far the most troublesome weed at both sites (Appendix 1). Broadleaf weed infestation was much higher in safflower and yellow mustard, for which there are no labeled herbicides, compared to cereals where in-crop herbicides were effectively utilized.

Impacts of Rhizoctonia Root Rot
Percent land area infected by Rhizoctonia root rot at the Adams county site has been presented in previous STEEP reports. It is highly unlikely that the severe patches caused by Rhizoctonia solani AG8 in the first wheat crop following two consecutive broadleaf crops were due to survival of the pathogen in old wheat residue over the two years since wheat was last grown in these plots. Even a short period of fallow can greatly reduce the severity of this disease. It seems more likely that, since all crops in these systems are hosts and since the period of time from planting (mid March to early April) to harvesting (August for mustard, barley, and wheat and September for safflower) was approximately the same, the amount of primary inoculum for production of Rhizoctonia root rot in the next crop was also then approximately the same.

The wide host range of R. solani AG8 has been well documented. Nevertheless, different kinds of crops have diverse effects on the soil environment, they have tap versus fibrous root systems, and they produce various amounts of crop residue or the residue decomposes at different rates when left on the soil surface in no-till systems. Depending on the extent of these differences, the amount of disease in this low-precipitation area could also differ, at least between systems as dissimilar as our original (1997-2000) 4-year rotation and the continuous wheat system. The original 4-year rotation was designed to augment any benefit of broadleaf crops for control of root disease by including two broadleaf crops back-to-back before returning to wheat. Previous studies on rotational effects of broadleaf crops have been limited to a single broadleaf crop as a break crop before wheat.

In spite of the differences in crops and rotations, the incidence and severity of both Rhizoctonia root rot were similar if not the same on wheat whether the cropping system was continuous wheat, a 2-year barley-wheat rotation, or a 4-year safflower-mustard-wheat-wheat rotation. An in-depth report on the epidemiology of Rhizoctonia in this study will be published by Cook et al. in the journal Plant Disease and in Wheat Life in 2002. In this study, broadleaf crops provided no benefit for Rhizoctonia root disease control and left less soil water available for the ensuing one or two cereal crops, thus growers in low-precipitation areas on the inland PNW are probably better off to plant continuous cereals.

INTERACTION WITH OTHER SCIENTISTS CONDUCTING RELATED ACTIVITY:

In addition to the co-investigators of this project, the PI is cooperating with: Doug Young, WSU Pullman, on economic evaluation of spring wheat vs. winter wheat-fallow in the Horse Heaven Hills; Ann Kennedy, USDA-ARS Pullman, on soil microbiology of dryland and irrigated cropping systems at Lind; Roger Veseth, WSU/UI Moscow, on cropping systems technology transfer; Don Wysocki, OSU Pendleton, on irrigated cropping systems research at Lind; Tim Paulitz, USDA-ARS Pullman on diseases in irrigated cropping systems at Lind; Kim Campbell, USDA-ARS Pullman, on winter wheat seedling emergence; and Frank Young, USDA-ARS, on the Ralston project. In addition, during 2001 the PI wrote an invited book chapter entitled "Dryland cropping in the western United States" for the American Society of Agronomy with co-authors Robert Papendick, USDA-ARS Pullman (retired); Stephen Guy, University of Idaho; Paul Rasmussen, USDA-ARS Pendleton (retired); and Chris van Kessel, University of California at Davis.

PUBLICATIONS AND PRESENTATIONS (2001 only):

Refereed Journal Articles
Cook, R.J., W.F. Schillinger, and N.W. Christensen. Rhizoctonia root rot and wheat take-all in diverse direct-seeded spring cropping systems. Plant Disease (submitted).

Published Abstracts
Schillinger, W.F., and R.J. Cook. 2001. Rhizoctonia root rot in diverse wheat-based no-till cropping systems. Crop Science Society of America annual meeting 21-25, Oct., Charlotte, NC. ASA, CSSA, and SSSA Abstracts.

Experiment Station Research and Extension Reports
Schillinger, W., R. Jirava, R.J. Cook, D. Young, H. Schafer, A. Kennedy, N. Christensen, G. Giri. 2001. Long-term alternative crop rotations using no-till: The first four years in Adams county. pp. 91-94. In: 2001 Field Day Proceedings: Highlights of Research Progress. Department of Crop and Soil Science Technical Report 01-4, Washington State University, Pullman, WA.

Field Tours
A twilight tour of cropping systems study at the Jirava farm near Ritzville was held on June 27, 2001. 30 attended.

Appendix 1. Average population (number/sq yard) and dry biomass (lb/a) of major weeds measured just before grain harvest at Adams County and Douglas County cropping systems research sites from 1997-2000.

¹ Adams County includes lambsquarter, prostrate knotweed, cheatgrass, pigweed, volunteer wheat, volunteer barley and Canadian thistle.
Douglas County includes lambsquarter, pigweed, mustard, annual bursage, cutleaf nightshade, fiddleneck, pennycrest and volunteer wheat.
² Mass measurements for Adams Co. were not collected in 1997, and therefore include only three years, 1998-2000.
³ 1st- and 2nd-year wheat after broadleaf crop not included in 4-year analysis since not available until 1998 and 1999, respectively.
⁴ Continuous s. wheat data used for two-year rotation wheat after barley in 1997.

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