Frank Young, Research Agronomist, USDA-ARS, Pullman, WA;

Kim Kidwell, Spring Wheat Breeder and Geneticist, WSU, Pullman, WA;

Bill Pan, Soil Scientist, WSU, Pullman, WA; Curtis Hennings, Grower, Ritzville, WA.


The major farming practice in the arid and semiarid regions of the PNW is a winter wheat-fallow rotation. This system is characterized by soil erosion, reduced soil quality, high incidence of winter annual grass weeds and diseases. It is thought that continuous no-till spring cropping of cereals will reduce the number of fallow fields, increase residue cover on fields in the summer and fall, increase soil quality, and reduce the potential of wind blown dust. However, there are no current established best management practices for continuous, no-till spring cropping systems. Little information is known on nutrient management strategies, crop varieties, crop planting date and rate, and pest problems associated with dryland spring cropping systems.

In the fall of 1995 an integrated/multidisciplinary long-term research field project was initiated in the 11-inch rainfall area near Ralston, WA. The objective of the study is to develop an economically and environmentally feasible no-till, continuous spring cropping system to replace or supplement the traditional winter wheat-summer fallow system. The multidisciplinary, long-term research project has two components, each with their separate, but coordinated objectives. The first component includes several small satellite studies for determining fertility, pest management, and other agronomic practices for producing specific market classes of spring wheat and spring barley in conservation tillage systems. The main research component is a field-size, long-term integrated spring crop management project with emphasis on spring wheat management. A team of 14 scientists and extension personnel from nine disciplines has been assembled to address these interdisciplinary research issues.

The second component is a large-scale, five-year field project that will evaluate four cropping systems: a) soft white winter wheat/fallow; b) soft white spring wheat/fallow; c) continuous hard red spring wheat; and d) hard red spring wheat/spring barley rotation. The soft white wheats have been selected for use in the fallow cropping systems because high soil moisture levels will improve grain yields and lower grain protein contents. Hard red spring wheat was selected for the continuous spring wheat/barley systems to take advantage of elevated protein levels in grain produced under limited moisture. A 20-acre site in the semiarid region has been procured to conduct this field study. Sufficient land is available to grow every crop every year. For most operations, field-size equipment will be used.

The 1996-97 crop year marked the successful establishment of all appropriate crop rotation cycles. The annual precipitation in this normal 11-inch rainfall zone was 16 to 17 inches and enabled all crops to produce excellent yields. The importance of preserving surface field residues to prevent soil erosion is well-known, however, information on how to manage existing crop residue is limited. The soil surface residue in no-till systems affect the amount of soil erosion, nutrient availability, soil structure, soil temperature, water evaporation, microbial activity, and pest incidence. Little information is present regarding cultivar and species affect on the above parameters. Beginning in March, 1996 soil and plant samples have been collected from the main Ralston Project and the annual spring cropping trial satellite study for soil quality and residue decomposition rates. Samples for soil quality are being analyzed for aggrate size distribution, pH, electrical conductivity, readily mineralized carbon, microbial biomass, dehydrogenase enzyme activity, and fatty acid methyl esters (FAME). Principal component analyses of FAME from 1996 foil samples showed separation by treatment and tillage (fallow or stubble) indicating differences in biological groupings.

Plant residue samples were collected at harvest in 1996 and 1997 for several varieties of winter wheat, spring wheat, and spring barley and analyzed for their fiber contents. The first portions to degrade are the soluble carbon compounds, then hemicellulose, cellulose, and then lignin. Using fiber analyses, there was significant differences in the amounts of soluble carbon, hemicellulose, cellulose, and lignin among the cultivars of spring wheat, spring barley, and winter wheat. At all sampling times, there was a difference in the rate of straw decomposition among species and cultivars. Thus far, for most of the straw analyses, high cellulose and low lignin content indicate rapid straw decomposition. It appears as though rate of straw decomposition for winter wheat and spring barley is predictable from fiber data.

For the past two growing seasons plant diseases have been quantified and evaluated for the four cropping systems at Ralston, WA. In the fall of 1996, up to 23% of the winter wheat roots were severed by Rhizoctonia root rot. In the spring of 1997, Rhizoctonia root rot was present on 80 and 98% of the seminal and crown roots respectively. Fusarium foot rot lesions were present on 58% of the plants. In no-till spring crops, Rhizoctonia root rot and take-all were the most important diseases. Rhizoctonia damage was severe on up to 85% of the seminal roots and did not vary among cropping systems. In contrast, crown root damage for hard red spring wheat after barley < continuous hard red spring wheat < soft white spring wheat after fallow < spring barley after HRSW. Take-all was present on 15% of the seminal roots and was greatest on spring barley and least on HRSW after barley.

In WA and ID, spring planted wheat and barley are at a greater risk of aphid-induced injury than are fall sown crops. For both crop growing seasons, insect incidence and management recommendations have been documented based on frequent counts during the season. Compared to 1996 aphid populations were very low in 1997, and never reached economic thresholds. Of economic importance, predacious ladybird beetles, especially (Coccinella septempunctata) maintained English grain aphid populations below economic levels.

The two predominate weed species in this study are downy brome (Bromus tectorum) and Russian thistle (Salsola iberica). In the 1996-97 growing season, both a fall and spring application of metribuzin (lexone/sencor) were applied to control downy brome in winter wheat. In addition, crop population was not uniform and 2,4-D was applied to suppress Russian thistle. In the no-till spring cereal systems, downy brome was controlled with Roundup (glyphosate) before seeding. Control was incomplete because some weeds were covered by crop residue. In this case, downy brome did not affect crop yield, but was able to produce ample seed to reinfest later crops. Russian thistle was prevalent in all spring crops and had to be controlled with a herbicide. Because of multiple flushes, some Russian thistle escaped and were controlled postharvest with a selective sprayer.

Soil water and water use efficiency has been measured and calculated respectively for both growing seasons at the Ralston Project site. In the summer of 1996 more water was stored in the conventional summer fallow (8.9 inches) compared to no-till, chem-fallow (6.6 inches). The lower water storage in no-till fallow was because of water use by Russian thistle. These weeds continued to utilize water after being sprayed with a sub-lethal rate of 2,4-D. Also in 1996, spring planted safflower on summer fallow used more water than winter wheat on fallow.

In the annual cropping response trial for spring grains, 12 spring wheat and 12 spring barley varieties were selected for agronomic evaluation based on preliminary data for fiber characteristics. Varieties were evaluated in no-till and conventional-till environments and at two locations - Ralston with an 11 inch rainfall and Dusty with 16 inch rainfall. At Ralston, grain yields of both spring wheat and barley were reduced 20% in small, no-till plots. In 1998, seeding rate and nitrogen fertilization will each be increased 10 to 15% compared to conventional tillage.

Economic analysis will occur in 1999- 2001 at the end of the experiment. However, for each year crop yield, protein, and all production costs will be recorded. At the end of the study crop production systems will be ranked both by average profitability and risk. Because of abundant and timely rainfall during the 1996-97 growing season, yields were excellent (Table 1).


Table 1. Crop yields for the 1996-97 spring cropping project at Ralston, WA.

Crop system Yield Test wt. Protein
WW/Fallow 58 bu 61.8 13.4%
SW/Fallow 55 bu 62.5 10.0%
HRSW/HRSW 50 bu 61.4 13.0%
HRSW/SB 50 bu 61.9 13.4%
SB/HRSW 1.67 T 51.6 8.7%

WW = winter wheat; SW = soft white spring wheat; HRSW = hard red spring wheat; SB = spring barley.

In 1997 winter wheat (Lewjain) produced on traditional fallow yielded 58 bu/A (0% moisture) which was 5 to 15 bu less than adjacent fields. Yield was lower because the winter wheat was replanted because the soil crusted after a late fall hail storm, and a heavy infestation of downy brome was present. Inputs were also high in this system. Seed was purchased twice, starter fertilizer was added for the second planting, and three separate applications of herbicides were used to control weeds. Soft white spring wheat (Alpowa) produced 55 bu/A on chem-fallow. In both the continuous no-till rotations (HRSW/HRSW and HRSW/SB) hard red spring wheat yielded 50 bu/A. Wheat in these two systems did not make protein (14%) and therefore would not receive premium price. But the higher than normal yield (50 bu) would offset this penalty somewhat. Spring barley, even though it was severely infected with Rhizoctonia foot rot, yielded 1.67 T/A which was approximately 175% more than in 1996. Thus far, the experimental site has received 127% and 145% more precipitation for the first two growing seasons than the long-term average.