Increased Cropping Intensity for Dryland with No-Till Barley

Chapter 2 – Conservation Tillage Systems and Equipment, May 1999
Pacific Northwest Conservation Tillage Handbook Series No. 24

Authors: William Schillinger, WSU Dryland Research Agronomist, Ritzville, WA; Donald and Doug Wellsandt, Growers, Ritzville, WA; R. James Cook, WSU Plant Pathologist / Endowed Chair in Wheat Research, Pullman, WA; Robert Papendick, Retired USDA-ARS Soil Scientist, Pullman, WA; and Harry Schafer, WSU Research Technician, Ritzville, WA.

Abstract

For most of a century the wide spread practice of growing only one crop every other year in a tillage-based wheat (Triticum aestivum L.) – fallow rotation has degraded soils and contributed to environmental problems in low-precipitation (less than 14 inch annual) dryland regions of the inland Pacific Northwest of the USA. Many growers in this 3.5-million-acre cropland area are increasing the intensity of cropping with spring crops, but most use conventional tillage (CT) for seedbed preparation. The agronomic performance of spring barley (Hordeum vulgare L.), sown both into CT seedbeds with double-disc drills and standing stubble with several types of no-till (NT) drills (hoe, single disc, and notched coulter), was determined in two experiments conducted both in 1996 and 1997 where the previous crop was either winter wheat or spring barley. We measured stand establishment, seed-zone temperature, soil water, dry biomass accumulation, Rhizoctonia root rot, surface residue retention, and grain yield components. Plant stand, dry biomass accumulation, and spike density as single independent variables, and combined in a multiple regression model, were strongly correlated (P < 0.001) to grain yield. Early-season seed-zone temperatures were cooler under NT, but seed-zone water was slightly higher with CT. Low spike density consistently occurred in a wide row spacing (16 in.) NT drill treatment, and the highest overall yields were obtained with NT drills with rows spaced 10 inches or less. Rhizoctonia root rot was severe on seminal roots in all treatments in three out of four trials but did not appear to limit yields, possibly due to healthy crown roots and favorable growing conditions. No-till spring sowing into undisturbed (2160 to 4670 lb./acre) standing stubble can produce grain yields equal to or exceeding those under CT and provide environmental and potential soil quality benefits for low-precipitation dryland farming areas in the inland Pacific Northwest.

Introduction

Farming in the dryland areas of the Pacific Northwest (less than 14 in. annual precipitation) 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 (Rasmussen and Parton, 1994). 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 (Papendick and Parr, 1997). Options for maintaining and improving soil quality in the drylands are to simultaneously increase the cropping intensity and reduce or eliminate tillage. The use of spring cropping in combination with no-till sowing would appear to offer the best approach for increasing cropping intensity, improving soil quality, and controlling erosion in the conventional fallow areas (Papendick, 1998). However, research with spring crops, and in particular with no-till in the dry areas of the inland Pacific Northwest, is limited.

Ciha (1983), in studies with annual spring wheat over 4 years and at two low-precipitation (9.4 and 12 in. annual) sites in eastern Washington, reported that fall chiseling plus light spring tillage consistently produced higher yields than from spring tillage alone or no-till. This study showed that even with the best yields the annual spring wheat was not competitive on an economic basis with conventional winter wheat-fallow because grain yields were not sufficient to offset increased production costs with spring cropping unless winter annual grassy weeds were a major problem in winter wheat. However, Ciha (1983) used a hoe drill with 14-in. row spacing, which is now considered excessively wide for spring cereals. There has since been rapid development and improvement of: (i) no-till drill technology, (ii) higher-yielding spring cereal cultivars, (iii) effective and affordable herbicides and, (iv) the understanding for timely and effective elimination of volunteer cereals (“green bridge”) for root disease control; and research efforts to develop intensive and diversified cropping systems using no-till in low-precipitation dryland areas have been renewed (Schillinger et al., 1998; Young et al., 1998).

Spring barley is another option with no-till spring sowing and is well adapted to the dry zones. One cropping sequence that has potential is winter wheat-spring barley-fallow, or even barley two years in a row with the barley no-tilled into the crop stubble. Minimum or delayed minimum tillage fallow or chemical fallow practices can be applied after the barley crop which provides a management option with a high potential for erosion control for the spring cropping system.

Rhizoctonia root rot caused by Rhizoctonia solani (Kühn) AG8 is the most important disease of spring barley sown directly into cereal stubble under Pacific Northwest conditions (Ogoshi et al., 1990; Pumphrey et al., 1987; Weller et al., 1986). This is a minor disease of wheat and barley grown with conventional tillage but can be devastating on these crops in no-till cropping systems (Smiley et al., 1992), confirming reports from Australia (Rovira, 1986). The two most effective practices shown to limit the severity of this disease in no-till cropping systems are (i) elimination of volunteer and other grass hosts of the pathogen 2-3 weeks and preferably 2-3 months before sowing the barley or wheat (Smiley et al., 1992), and (ii) soil disturbance in the seed row 2 inches below the seed at the time of sowing (Roget et al, 1996).

The objective of our study was todevelop “one-pass” methods of sowing spring barley directly into undisturbed standing stubble that are equal (or superior) to conventional sowing methods involving tillage. Specific objectives were to determine the effects of no-till vs. conventional tillage-based sowing methods on: stand establishment, seed-zone temperature, seed-zone water loss, dry biomass accumulation, Rhizoctonia root rot, residue retention for erosion control, and grain yield components.

Materials and Methods

Two studies were conducted at two sites in 1996 and 1997 on the Donald and Doug Wellsandt farm in Adams county, Washington. Annual precipitation at the sites averages 12.7 inches with 70% occurring between 1 August and 31 March (Table 1). The soil is a Walla Walla silt loam (Typic Haploxeroll, coarse-silty, mixed, mesic) derived from loess overlying basalt bedrock. The depth of the soil is greater than 6 feet.

Treatments and Field Layout

In both years, the two experiments were on adjacent 7.5 acre-parcels where the previous crops were winter wheat and spring barley, respectively. Stubble from the previous crops was left undisturbed from harvest in August through February. In early March, 12 oz./acre glyphosate herbicide (Roundup Ultra) was applied to both plot areas to control winter annual grassy weeds and volunteer from the previous crop.

The experimental design for both experiments each year was a randomized complete block with four sowing treatments replicated four times. Plots were 300 ft long x 70 ft wide on average, although the plot width for each treatment varied from 32 to 90 ft according to the size of field machinery and drills. The treatments were: (i) conventional tillage (CT) and fertilization to create a relatively bare soil surface, followed by sowing barley with a double-disc drill; (ii) direct sowing with a hoe-type no-till (NT) drill that aggressively disturbed the soil beneath the seed and moved residue from the seed row; (iii) direct sowing with a single-disc or coulter-blade NT drill, where slight disturbance beneath the depth of seed placement was limited to that caused by the single disc or coulter blade, and; (iv) direct sowing with a modified John Deere HZ deep furrow hoe-type drill with wide (16 in.) row spacing. The John Deere HZ is the standard drill for sowing winter wheat into tilled summer fallow in the inland Pacific Northwest. Specifications of each drill used in the study and method of fertilizer delivery are shown in Table 2.

Table 1. Annual precipitation (inches) during the 1995-1996 and 1996-1997 crop cycles compared to the 20-year average near Ritzville, WA.†

Baseline surface residue in March (i.e., undisturbed from the previous crop) was 2160 and 2840 lb./acre for barley stubble and 3220 and 4670 lb./acre for winter wheat stubble in 1996 and 1997, respectively. Land preparation for the CT treatment in 1996 for both winter wheat and spring barley stubble was single tillage passes using farm-size equipment through the plot with: i) a 5-bar “super” harrow with 24-inch-long tines; ii) cultivator operating 3 inches deep with straight-point shanks with “K” plates spaced 6 in. apart with an attached short-tooth harrow and; iii) fertilizer injection with shanks spaced 1 ft apart and 4 in. deep with attached 5-bar tine harrow. In 1997, CT seedbed preparation was single passes through the plots with: i) a tandem disc with 24-inch-diameter blades spaced 9 in. apart and set to a soil depth of 3 in. with attached 5-bar flex harrow and; ii) fertilizer injection with shanks spaced 1 ft apart and 4 in. deep with attached 5-bar harrow.

Fertilizer and seed rate in all plots was held constant across treatments each year. Barley seed was treated with a broad-spectrum fungicide/insecticide (Triazole-Thiram-Lindane) both years. The fertilizer rate (based on soil test with a yield goal of 1.8 tons/acre) was 70 lb. N, 14 lb. P, and 10 lb. S per acre in 1996 and 75 lb. N, 13 lb. P, and 9 lb. S per acre in 1997. In the CT treatment, all N and S were applied as liquid in either aqua NH₃ plus ammonium thiosulfate (1996) or urea-ammonium nitrate solution (Solution 32) plus ammonium thiosulfate (1997). Phosphorus was applied with the seed as granular monoammonium phosphate at the time of sowing in 1996, and pre-sowing as ammonium polyphosphate solution in 1997. All NT drills delivered seed and all fertilizer in one pass through the plots (Table 2). Plots were sown to barley at 70 lb./acre with cv. ‘Baronesse’ between 28-31 March in 1996, and with cv. ‘Camelot’ on 7-8 April in 1997. Soil covering seed was about 1.2 inches in all treatments during both years. Broadleaf weeds were effectively controlled during the growing season with 0.5 lb. active ingredient per acre bromoxynil (Buctril) applied in the tillering stage of growth.

Root Disease Assessment

Plants were collected from the plots at Feekes growth stage (Large, 1954) 5 (leaf sheaths strongly erect) in 1996, and at Feekes growth stage 10.5 (anthesis) in 1997. Rhizoctonia root rot is predominantly confined to the top 4 inches of soil. Roots from at least five plants in the top 6 inches of soil were dug from each of five separate locations within every plot. This composite sample typically amounted to 30-40 plants per plot, from which 25 plants were selected at random. The roots were washed with water in preparation for assessment of the incidence and severity of Rhizoctonia root rot. We concentrated on the seminal roots by counting both the total number and the number girdled or severed by a Rhizoctonia lesion and then dividing the number infected by the total number to determine percentage infection. We also rated the seminal roots on each plant for severity of Rhizoctonia root rot on a 0-8 scale, where: 0 = no lesion evident; 1 = <50% roots with a single typical sunken lesion; 2 = < 50% roots with a few brown sunken lesions; 3 = > 50% roots with a few brown sunken lesions; 4 = < 50% roots with brown sunken lesions within 0.4 in. from the seed; 5 = > 50% roots with brown sunken lesions within 0.4 in. from the seed; 6 = > 50% roots shorter than 1.2 in. from the seed; 7 = > 50% roots shorter than 0.4 in. from the seed; 8 = almost no roots with stunting or death of seedling.

Water, Soil Temperature, Stand Establishment, Dry Biomass, and Residue Measurements

Water content in the 6-ft soil profile was measured in all plots each spring before sowing and again after harvest. Soil volumetric water content in the 0- to 1-ft depth was determined from two 6-in. core samples using gravimetric procedures, and in the 1-to 6-ft depth in 6-in. increments by neutron attenuation (Gardner, 1986). Additionally, mass water content in the 0- to 2-, 2- to 4-, and 4- to 6-in. soil depths in the seed row was measured on several sampling dates within 6 weeks after sowing on three soil cores per plot.

Soil temperature at seed depth was determined on the same dates as surface soil water measurements (i.e., several times within 6 weeks after sowing). Eight soil thermometers were placed with sensors 1.2 in. below the soil surface in the seed row at the depth of seed placement of each plot and allowed to equilibrate 4 minutes before recording readings and moving to the adjoining plot. Temperature readings generally took five hours to obtain (eight readings x four treatments x four replications x two trials) during which soil temperatures fluctuated; however, readings within each replication were completed within 30-minute intervals.

Barley stand establishment was measured by counting individual plants in 1-m row segments 25 days after sowing. Three row segments were selected and marked within each plot prior to seedling emergence. Barley dry biomass accumulation was determined by clipping all above-ground plant material in three 1-yard-long row segments, and making a unit area conversion based on row spacing, for each treatment several times during the growing season.

Surface residue from the previous crop was measured from all plots prior to sowing, soon after sowing, and again after grain harvest in August by gathering all aboveground dry biomass within a 3-ft-diameter hoop. In the August sampling, current year (i.e., newly harvested) residue was separated from year-old residual residue. Samples were placed in paper bags and allowed to air-dry in a low-humidity greenhouse before weighing.

Yield Components

Yield was determined by harvesting a 25-ft-wide swath through each 300-ft plot with a commercial combine and auguring grain into a weigh wagon. Spike density and total dry biomass production were measured by hand-cutting the above-ground plant from 3-ft row segments in three locations in each plot at harvest in August. Unit area for the clipped row of each treatment was then calculated based on drill row spacing. Kernels per spike was calculated based on spikes per ft² and 1000 kernel weight after passing spikes though a hand-fed thresher.

Table 2. Specifications of conventional and no-till seed drills used to sow spring barley in research trials conducted near Ritzville, WA, in 1996 and 1997.

Analysis of Data

Analysis of variance was conducted for treatment differences in barley stand establishment, seed-zone temperature, seed-zone water content, total water in the 6 ft profile, severity of Rhizoctonia root rot, dry biomass accumulation, surface residue, and grain yield components. Treatment means were separated using Fisher’s protected least significant difference. Treatments were considered significantly different if the P-value was <0.05. Simple and multiple regression models were calculated to determine the association of plant stand, dry biomass accumulation, spike density, kernels per spike, kernel weight, and Rhizoctonia severity to grain yield.

Results and Discussion

Precipitation, Water Storage, and Air Temperature

Over-winter (August-through-March) precipitation at the study site was 10 inches in 1995-1996 and 16 inches in 1996-1997 compared with the 20-year average of 8.9 inches (Table 1). Soil water in the 6-ft soil profile ranged from 13.5 to 16 inches in early spring before sowing in 1996 and 1997 (Table 3), respectively, which is wetter than average (about 10.2 inches) for the area. Growing season (April-through-July) precipitation in 1996 and 1997 was slightly below the 20-year average (Table 1), but May and June rains were timely. Maximum air temperature rarely exceeded 90⁰ F during either the 1996 or 1997 growing season (data not shown), which probably raised the yield potential.

Plant Stand Establishment

Soil surface roughness, method of sowing, and seed opener configuration on the drill each affected barley stand establishment both years. In 1996, there were no differences in stand establishment after sowing into the relatively smooth-surfaced barley-stubble seedbed, whereas stands were significantly better with CT than with any of the NT treatments after sowing into the deep-furrowed winter-wheat-stubble seedbed (Table 4). Plant stands in winter wheat stubble were lowest for the John Deere 752 disc drill because uniform soil penetration and seed placement could not be maintained while sowing perpendicular to the tall, 16-inch-wide, winter wheat furrows. Stands were better with the Flexi-coil 5000 and John Deere HZ drills equipped with hoe openers that more aggressively penetrated through furrow ridges and disturbed the soil in the seed row (Tables 2 and 4).

Highly significant differences in plant stand among treatments were measured in 1997. The best stands were achieved with the Cross-slot and Concord NT drill treatments (Table 4). The CT treatment received fewer tillage operations in 1997 compared with 1996 and therefore had a rougher, more cloddy seedbed than in the previous year, possibly accounting for the poorer stand. Stand density was lowest for the John Deere HZ drill with the wide row spacing.

Table 4. Plant stand establishment of spring barley in 1996 and 1997 as affected by conventional tillage and no-till sowing method and the previous crop. Measurements were obtained 25 days after sowing. Drill type is indicated in parenthesis after each sowing treatment.

Surface Soil Temperature and Water Content

Soil temperature at the depth of seed placement varied among NT treatments relative to CT during the early growing season, but was generally cooler with no-till. Differences between one or more of the NT treatments compared with CT were obtained on four of five measurement dates in 1996 in both barley stubble and winter wheat stubble (Fig 1). In 1997, there were no differences in soil temperature in barley stubble, but all NT treatments were cooler than CT on all sampling dates in winter wheat stubble (Fig 1). The high quantity (up to 4670 lb./acre) of surface residue remaining after sowing likely increased solar reflectively and soil surface insulation (Johnson and Lowery, 1985; Ross et al., 1985) in the NT treatments compared with CT.

Shallow soil water content during the early growing season was variable among treatments and measurement dates, especially in the 0 -to 2-in. depth, but tended to be wetter with conventional tillage at the 2 -to 4- and 4-to 6-in. depths for both years (Figs. 2 and 3). Early growing season (1 April – 15 May) precipitation was 1.50 and 1.46 inches in 1996 and 1997, respectively, compared with the long-term average of 1.18 inches. Non-tilled soils are considered more efficient for water conservation of spring-sown crops because tillage of moist soils in the early spring breaks soil capillary and macro pore continuity and accelerates soil drying above the depth of tillage. Additionally, infiltration generally is less through tilled than non-tilled soils because a greater amount of precipitation is required to wet the dry tillage layer, and to reestablish capillary continuity before water penetrates to deeper layers (Steiner, 1994). On the other hand, breaking soil capillary with tillage has long been known to be effective in retarding evaporative loss of soil water from beneath the tillage depth (McCall, 1925). Barley seed in the CT treatment was placed 0.6 in. below the tilled layer (i.e., into non-tilled soil), and we speculate that water conservation was not diminished relative to the NT treatments because the abrupt break of soil capillary with tillage helped to conserve water in the seed zone.

Rhizoctonia Root Rot

Rhizoctonia root rot generally was severe on the seminal roots of spring barley in both 1996 and 1997, regardless of the method of sowing or previous crop (Table 5). In previous studies, we have not found a yield impact with Rhizoctonia severity ratings below 3.0, but have shown limitations to yield with ratings of 4-5 and above (R.J. Cook unpublished data). In contrast to the high percentages of infection of seminal roots, the crown roots, although not included in the assessment, were free of infections, presumably because the inoculum potential of the pathogen in the soil had declined by the time these roots were formed. Each lesion that collectively makes up Rhizoctonia root rot is a separate infection initiated from the primary inoculum in the soil and, because the viability of this primary inoculum declines over time, there can be markedly less primary inoculum when crown roots form compared to when seminal roots form. One exception was in 1996 when the disease on seminal roots was relatively mild following spring barley (Table 5). In that same year, with severe disease after winter wheat, Rhizoctonia was more acute in the CT treatment, where seed was sown about 0.6 in. below the tilled layer into undisturbed soil with double-disc openers, than in the Flexi-coil and JD HZ treatments equipped with hoe-type openers that aggressively disturb the soil below the seed.

Rhizoctonia infection was again limited to the seminal roots in 1997 where it was severe regardless of whether the site was in winter wheat or spring barley the previous year and regardless of the method of sowing. Plants from plots sown with the JD HZ drill had the highest Rhizoctonia root rot severity rating, but otherwise there were no differences among the treatments (Table 5).

Table 5. Influence of method of sowing on severity of Rhizoctonia root rot of spring barley in 1996 and 1997 where the previous crop was either spring barley or winter wheat. Plant samples were collected at Feekes growth stage 5 (leaf sheaths strongly erect) on 16 May, 1996, and at Feekes growth stage 10.5 (anthesis) on 17 June, 1997.

Dry Biomass Accumulation and Yield Components

Above-ground dry biomass accumulation during the growing season was strongly influenced by stand establishment (r² = 0.92, P <0.001, data not shown). There were highly significant differences in dry biomass among treatments on all sampling dates during both years, and the rank order among treatments remained the same, with few exceptions, throughout both growing seasons (data not shown). Dry biomass for the John Deere HZ was lowest of any of the NT treatments in all four sowing trials, except for CT in 1997 (data not shown).

Analyzed across locations, grain yield was significantly greater when the previous crop was spring barley rather than winter wheat for conventional tillage (1996 and 1997), the single disc JD 752 (1996) and notched-coulter Cross-slot (1997) treatments; but yield with hoe opener drill treatments (i.e., Flexi-coil 5000, JD HZ, and Concord 1100) was not affected by previous crop (Table 6, combined ANOVA not shown). Yield reductions with the non-hoe-opener treatments may be largely due to the hard, less penetrable, surface soil and the deep furrows in the winter wheat stubble, whereas the spring barley stubble seedbeds had a smoother, mellower, surface soil condition.

Grain yield generally improved in the two experiments in both years proportional to increased spike density (Table 6). Spike number per unit area is considered the most important yield component for wheat and barley under dryland conditions when severe water stress is not a factor (Arnon 1972). The John Deere HZ treatment always had the lowest spike density and, although it compensated with greater kernel weight and numbers per spike, was not competitive for grain yield with other no-till treatments, except when sown into winter wheat stubble in 1996. The CT treatment produced more grain than any of the NT treatments in 1996, when the previous crop was either barley or winter wheat, but the Cross-slot and Concord NT treatments out-produced CT in 1997 (Table 6).

Simple linear regression models show that stand establishment, dry biomass accumulation, and spike density were significantly related to grain yield in 1996, 1997, and in a combined 1996 plus 1997 analysis (Table 7). In multiple regression models, stand, dry biomass, and spike density collectively accounted for 79, 92, and 81% of yield variability in 1996, 1997, and 1996 plus 1997, respectively (Table 7). Kernels per spike was related to yield differences in 1997, but not in 1996 or in the combined 1996 plus 1997 regression analysis. Kernel weight and Rhizoctonia root rot severity were not correlated with yield differences among treatments during either year (Table 7).

Crop Residue

Only 490 to 800 lb./acre of year-old residue remained in the CT treatment vs. 1180 to 4620 lb./acre for the NT treatments during the two years (Table 8). The ultra-low-disturbance Cross-slot drill retained more surface residue (except for JD HZ, which equaled Cross-slot after barley stubble) and disturbed the soil less than the other NT drill treatments. Mass of newly-harvested residue in the NT treatments was less than or equal to the CT treatment during both years. Total residue was higher for all NT treatments compared to CT in 1997, but not in 1996 (Table 8). Maintenance of barley residue on the soil surface is of particular importance to growers practicing a winter wheat – spring barley – fallow rotation in low-precipitation dryland areas of the inland Pacific Northwest because barley residue decomposes faster than wheat residue (Smith and Peckenpaugh, 1986). This often makes it difficult to meet minimum residue requirements for erosion control if soils are tilled during the 13-month fallow cycle.

Table 6. Grain yield components of spring barley in 1996 and 1997 sown either conventionally or no-till into spring barley stubble and winter wheat stubble.†

Table 7. Correlation coefficients of simple and multiple determination for regression models to describe the relationship of plant stand, dry biomass production, spike density, kernels per spike, kernel weight, and Rhizoctonia root rot severity to grain yield in 1996, 1997, and in 1996 plus 1997 combined.

Table 8. Year-old surface residue, newly-harvested surface residue, and total surface residue in August of 1996 and 1997 as affected by type of seedbed and method of sowing spring barley.

Summary and Conclusions

Plant stand establishment, rapid plant biomass accumulation, and thick spike density contributed to high spring barley grain yields during two years with favorable growing conditions. When uniform stands were achieved, no-till sowing into standing stubble was equal or superior for grain yield compared with conventional tillage. A no-till drill with wide (16 in.) row spacing was not competitive with other treatments because of low spike density and associated low yield; but yield did not decline with other NT treatments with row spacing as wide as 10 inches.

Rhizoctonia root rot was limited largely to seminal roots, where infections were severe in three of the four sowing trials. The severity of Rhizoctonia root rot on the seminal root system did not affect grain yield among treatments, or appear to limit yields, possibly because crops were sustained by the healthy crown roots during relatively non-stressful growing conditions. There was no consistent effect of sowing method on severity of Rhizoctonia root rot in any of the four experiments.

Early spring soil temperature was cooler with no-till, but seed-zone soil water was slightly higher with conventional tillage. Spring barley yields were always best for the disc-drill-type treatments (both CT and NT) when the previous crop was spring barley compared with winter wheat, probably because the winter wheat seedbed was harder, rougher, and less penetrable. No-till drill treatments retained from 1160 to 4550 lb./acre surface residue after sowing.

Soil organic carbon decline, soil erosion, and air and water pollution are major problems in low-precipitation dryland farming areas where tillage is often intensive and, historically, only one crop is produced every two years. Priority long-term research needs for development of continuous no-till and reduced-till systems include: further refinement of low-disturbance NT drills, which are effective under a variety of sowing conditions; agronomic and economic assessment of broadleaf alternative crops in cereal-based cropping patterns; gaining a better understanding of how increased cropping intensity/diversity affects pressures for soilborne pathogens and weeds and; documentation of biological and ecological soil changes that occur during the transition to no-till management systems.

Acknowledgements

Funding for this research was provided by the Washington Barley Commission and the Columbia Plateau Wind Erosion/Air Quality Project. The authors gratefully acknowledge the technical assistance and cooperation of the following individuals and companies: Hal Johnson, Grower, Davenport; Keith Saxton and John Driessen, USDA-ARS, Pullman; Jim Walter and Ed Deife, Walter Implement, Odessa; Howard Reimer, Ritzville Chemical, Ritzville; Dean Brown, Monsanto Co., Spokane; Curtis Evanenko, Flexicoil Co., Minot, ND; Bruce Sauer, WSU Dryland Research Station, Lind; Martin Palmer, Davenport; and Steve Schofstoll, Ritzville. Mention of product and equipment names does not imply endorsement by the authors.

References

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To simplify information, chemical and equipment trade names have been used. Neither endorsement of named products is intended, nor criticism implied of similar products not mentioned. For herbicide application recommendations, refer to product labels and the Pacific Northwest Weed Control Handbook, an annually revised extension publication available from of the University of Idaho, Oregon State University and Washington State University.

Pacific Northwest Conservation Tillage Handbook Series publications are jointly produced by University of Idaho Cooperative Extension System, Oregon State University Extension Service and Washington State University Cooperative Extension. Similar crops, climate, and topography create a natural geographic unit that crosses state lines in this region. Joint writing, editing, and production prevent duplication of effort, broaden the availability of faculty, and substantially reduce costs for the participating states.