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DRYLAND CROPPING SYSTEMS

Increased Dryland Cropping Intensity with No-Till Barley

^a Dep. of Crop and Soil Sciences, Dep. of Plant Pathology, and USDA-ARS, 201 Johnson Hall, Washington State Univ., Pullman, WA 99164-6420 USA

schillw{at}wsu.edu

	ABSTRACT

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion Summary and conclusions REFERENCES

 
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 (<350 mm annual) dryland regions of the inland Pacific Northwest of the USA. Many growers in this 2-million-ha 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 into CT seedbeds with double-disk drills or into standing stubble with several types of no-till (NT) drills (hoe, single disk, 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 (406 mm) NT drill treatment, and the highest overall yields were obtained with NT drills with rows spaced 255 mm 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 standing stubble (2420–5230 kg ha^-1) can produce grain yields equal to or exceeding those under CT and can provide environmental and potential soil quality benefits for low-precipitation dryland farming areas in the inland Pacific Northwest.

Abbreviations: CT, conventional tillage • JD, John Deere • NT, no-till

	INTRODUCTION

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion Summary and conclusions REFERENCES

 
FARMING IN THE DRYLAND AREAS of the Pacific Northwest (<350 mm 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 two-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 four years and at two low-precipitation (240 and 305 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 360-mm 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. Furthermore, 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 for 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 ordinarily a minor disease of wheat and barley grown with conventional tillage, but it can be devastating on these crops in no-till cropping systems (Smiley et al., 1992), as has also been seen in 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 to 3 wk and preferably 2 to 3 mo before sowing the barley or wheat (Smiley et al., 1992), and (ii) soil disturbance in the seed row 50 to 60 mm below the seed at the time of sowing (Roget et al., 1996).

The objective of our study was to develop 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

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion Summary and conclusions REFERENCES

 
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 322 mm, with 70% occurring between 1 August and 31 March (Table 1) . The soil is a Walla Walla silt loam (coarse-silty, mixed, mesic Typic Haploxeroll) derived from loess overlying basalt bedrock. The depth of the soil is greater than 2 m.

View this table: [in this window] [in a new window]   Table 1 Annual precipitation during the 1995–1996 and 1996–1997 crop cycles near Ritzville, WA, along with the 20-yr average.

The experimental design for both experiments each year was a randomized complete block with four sowing treatments replicated four times. Plots were 90 m long by 21 m wide on average, although the plot width for each treatment varied from 10 to 28 m, 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-disk 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-disk or coulter-blade NT drill, where slight disturbance beneath the depth of seed placement was limited to that caused by the single disk or coulter blade; and (iv) direct sowing with a modified John Deere HZ deep-furrow hoe-type drill with wide (406 mm) row spacing. The John Deere HZ is the standard drill for sowing winter wheat into tilled summer fallow in the inland Pacific Northwest.¹ Specifications of each drill used in the study and method of fertilizer delivery are shown in Table 2 .

Fertilizer and seed rate in all plots was held constant across treatments each year. Barley seed was treated in both years with a broad-spectrum fungicide and insecticide formulation of tebuconazole {-[2-(4-chlorophenyl)ethyl]--(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol} thiram [bis(dimethylthiocarbamoyl)disulfide], and lindane [1,2,3,4,5,6-hexachlorohexane]. The fertilizer rate (based on soil test with a yield goal of 4000 kg ha^-1) was 78 kg N, 16 kg P, and 11 kg S ha^-1 in 1996 and 84 kg N, 15 kg P, and 10 kg S ha^-1 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 (320 g N kg^-1) plus ammonium thiosulfate (1997). Phosphorus was applied with the seed as granular monoammonium phosphate at the time of sowing in 1996, and before 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 78 kg ha^-1 with `Baronesse' between 28 and 31 March in 1996, and with `Camelot' on 7 and 8 April in 1997. Soil covering seed was 30 mm in all treatments during both years. Broadleaf weeds were effectively controlled during the growing season with 0.56 kg a.i. ha^-1 bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) applied in the tillering stage of growth.

Root Disease Assessment
Plants were collected from the plots at Feekes growth stage 5 (leaf sheaths strongly erect) in 1996 and at Feekes growth stage 10.5 (anthesis) in 1997 (Large, 1954). Rhizoctonia root rot is predominantly confined to the top 100 mm of soil. Roots from at least five plants in the top 150 mm of soil (0.004 m³ soil volume for each sample) were dug from each of five separate locations within every plot. This composite sample typically amounted to 30 to 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, 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 scale of 0 to 8, 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 10 mm from the seed; 5 = >50% roots with brown sunken lesions within 10 mm from the seed; 6 = >50% roots shorter than 30 mm from the seed; 7 = >50% roots shorter than 10 mm 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 1.8-m soil profile was measured in all plots each spring before sowing and again after harvest. Soil volumetric water content in the 0- to 0.3-m depth was determined from two 0.15-m core samples using gravimetric procedures, and in the 0.3- to 1.8-m depth in 0.15-m increments by neutron attenuation (Gardner, 1986). Additionally, mass water content in the 0- to 50-mm, 50- to 100-mm, and 100- to 150-mm soil depths in the seed row was measured on several sampling dates within 6 wk 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 wk after sowing). Eight soil thermometers were placed with sensors 30 mm below the soil surface in the seed row at the depth of seed placement of each plot and allowed to equilibrate for 4 min 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 time soil temperatures fluctuated; within each replication, however, readings were completed within 30-min intervals.

Barley stand establishment was measured by counting individual plants in 1-m row segments 25 d 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 aboveground plant material in three 1-m-long row segments, and then 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 1-m-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 7.6-m-wide swath through each 90-m plot with a commercial combine and then augering grain into a weigh wagon. Spike density and total dry biomass production were measured by hand-cutting the aboveground plant from 1-m 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 unit area (m²) and 1000-kernel weight after passing spikes though a hand-fed thresher.

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 1.8-m 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

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion Summary and conclusions REFERENCES

 
Precipitation, Water Storage, and Air Temperature
Over-winter (August–March) precipitation at the study site was 254 mm in 1995–1996 and 406 mm in 1996–1997, compared with the 20-yr average of 227 mm (Table 1). Soil water in the 1.8-m soil profile ranged from 344 to 407 mm in early spring before sowing in 1996 and 1997 (Table 3) , respectively, which is wetter than average (260 mm) for the area. Growing-season precipitation (April–July) in 1996 and 1997 was slightly below the 20-yr average (Table 1), but May and June rains were timely. Maximum air temperature rarely exceeded 30°C during either the 1996 or 1997 growing season (data not shown), which probably raised the yield potential.

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 NT. 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 5180 kg ha^-1) of surface residue remaining after sowing probably increased solar reflectivity and soil surface insulation (Johnson and Lowery, 1985; Ross et al., 1985) in the NT treatments relative to CT.

View larger version (46K): [in this window] [in a new window]   Fig. 1 Early-season soil temperature variation 30 mm below soil surface at depth of seed placement in no-till sowing treatments compared with conventional tillage (zero line) on five dates in 1996 and three dates 1997 where the previous crop was spring barley or winter wheat. Numbers below bars indicate days without precipitation (DWP) preceding soil temperature measurement dates and maximum (MaxT) and minimum (MinT) air temperature on the days soil temperatures were recorded

View larger version (49K): [in this window] [in a new window]   Fig. 2 Early-season soil water variation at three depths in no-till treatments compared with conventional tillage (zero line) on five dates in 1996 where the previous crop was spring barley or winter wheat. Numbers below bars indicate days without precipitation (DWP) preceding each soil water measurement date

View larger version (41K): [in this window] [in a new window]   Fig. 3 Early-season soil water variation at three depths in no-till treatments compared with conventional tillage (zero line) on three dates in 1997 where the previous crop was spring barley or winter wheat. Numbers below bars indicate days without precipitation (DWP) preceding each soil water measurement date

Dry Biomass Accumulation and Yield Components
Aboveground dry biomass accumulation during the growing season was strongly influenced by stand establishment . 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 (Table 6) . 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 (Table 6).

View this table: [in this window] [in a new window]   Table 7 Grain yield components of spring barley in 1996 and 1997 sown either conventionally (CT) or with no-till equipment (described in Table 2) into spring barley stubble and winter wheat stubble.

Simple linear regression models show that stand establishment, dry biomass accumulation, and spike density were significantly related to grain yield in both years and in a combined 1996 plus 1997 analysis (Table 8) . 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 8). 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 8).

View this table: [in this window] [in a new window]   Table 9 Year-old surface residue, newly harvested surface residue, and total surface residue in August of 1996 and 1997 as affected by type of seedbed (conventional till, CT, or with no-till equipment, described in Table 2) and method of sowing spring barley.

	Summary and conclusions

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion Summary and conclusions REFERENCES

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, nor did it appear to limit yields, possibly because crops were sustained by the healthy crown roots during relatively nonstressful 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 disk-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 1320 to 5180 kg ha^-1 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 no-till drills that are effective under a variety of sowing conditions; agronomic and economic assessment of broadleaf alternative crops in cereal-based cropping patterns; better understanding of how increased cropping intensity and 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.

	ACKNOWLEDGMENTS

 
The authors thank Harry Schafer, Washington State University Agricultural Research Technician, for his valuable assistance. Appreciation is extended also to growers Donald and Doug Wellsandt for their active involvement in the research project and their donation of time, equipment, inputs, and land. Funding for this study was provided by the Washington Barley Commission and the Columbia Plateau Wind Erosion/Air Quality Project.

	NOTES

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion Summary and conclusions REFERENCES

 
Washington State Univ. Crop and Soil Sciences Dep. Technical Paper no. 9911-15.

¹ Mention of product and equipment names does not imply endorsement by the authors or by Washington State University.

Received for publication December 14, 1998.

	REFERENCES

TOP NOTES ABSTRACT INTRODUCTION Materials and methods Results and discussion Summary and conclusions REFERENCES

 

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This Article Abstract Figures Only Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (14) Citing Articles via Google Scholar Google Scholar Articles by Schillinger, W. F. Articles by Papendick, R. I. Search for Related Content PubMed Articles by Schillinger, W. F. Articles by Papendick, R. I. Agricola Articles by Schillinger, W. F. Articles by Papendick, R. I. Related Collections Crop Rotation Systems Dryland Cropping Systems Other Grain Crops Tillage