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WHEAT

Yield and Water-Use Efficiency of Eight Wheat Cultivars Planted on Seven Dates in Northeastern Oregon

^a Montana State Univ., Central Agric. Research Center, HC90 Box 20, Moccasin, MT 59462
^b Texas Agric. Exp. Stn., 2301 Experiment Station Rd., Bushland, TX 79012
^c Oregon State Univ., Columbia Basin Agric. Res. Center, P.O. Box 370, Pendleton, OR 97801
^d Oregon State Univ., Extension Service, Ballard Hall, Corvallis, OR 97331

^* Corresponding author (cchen{at}montana.edu)

Received for publication January 8, 2002.

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS NOTES RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Wheat (Triticum aestivum L.) yields in the inland Pacific Northwest are limited by inadequate water supply late in the growing season. Choosing a suitable planting date and genotype with the appropriate phenology that matches crop growth to the water supply will produce optimum grain yields. The objectives of this study were to investigate the effects of (i) planting and (ii) wheat genotype differences on grain yield, evapotranspiration (ET), and water-use efficiency (WUE). A 3-yr experiment was conducted on a Walla Walla silt loam (coarse-silty, mixed, mesic Typic Haploxeroll) near Pendleton, OR. Six winter and two spring wheat cultivars were planted in seven planting treatments (planting practices that include planting date, seeding rate, drill type, row space, and seeding depth). Soil water content was measured to determine ET. Planting treatments greatly influenced winter wheat yield. Different winter wheat cultivars responded differently to planting treatments. The optimum yield was produced at October plantings for all cultivars. Yield from September plantings was 745 to 1550 kg ha^-1 less than that from the October plantings, and yield also decreased when planting was delayed beyond October. For spring wheat, effect of planting treatments on yield was not statistically significant and there was no significant cultivar effect. Planting treatments significantly affected ET after adjusting for vapor pressure deficit (ET/VPD). Winter and spring wheat planted in the spring had approximately 380 to 650 mm kPa^-1 less ET/VPD (approximately 110–160 mm ET) than that planted in the fall. However, WUE was not significantly affected by planting treatments and cultivars.

Abbreviations: ANOVA, analysis of variance • ET, evapotranspiration • GSMDA-VPD, growing season mean daily atmospheric water vapor pressure deficit • MDA-VPD, mean daily atmospheric water vapor pressure deficit • VPD, vapor pressure deficit • WUE, water-use efficiency

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS NOTES RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
MORE THAN HALF A MILLION metric tonnes of wheat are produced annually in eastern Oregon. The region has a semiarid, Mediterranean-type climate in which 70% of the 250- to 450-mm annual precipitation falls during the winter months (October–March), and little to none is received from May to late August. A rapid transition in weather conditions from cold and wet to hot and dry occurs during the spring (Payne et al., 2001).

Wheat yield in the Pacific Northwest inland area is limited by inadequate storage of winter precipitation in the soil profile and unpredictable and low spring rainfall (Rasmussen et al., 1998), and has been found to be linearly related to the sum of soil water storage in March plus the amount of subsequent spring rain (Leggett, 1959). Rainfall distribution is as important as total rainfall to wheat growth and yield. Long-term experiments in northeastern Oregon indicate that, for a given amount of total rainfall, wheat yield is generally much higher if rain is partially distributed during spring months, particularly in May and June (Rasmussen et al., 1998). Optimum yield is usually received when crop phenology and growth match soil water availability (Fischer, 1979; Loss and Siddique, 1994).

Choice of seeding date and cultivar affects the synchronization of crop development with soil water availability, and can be used to match crop water demand to environmental conditions. For example, wheat yields increased in Western Australia when early sowing was used to match rainfall pattern to crop growth and water demand (Anderson and Smith, 1990; Kerr et al., 1992). In low-rainfall regions with limited spring water supply, short-season cultivars have out-yielded later-maturing genotypes (Stapper and Harris, 1989; Connor et al., 1992; Kerr et al., 1992; Coventry et al., 1993).

Early seeding may be constrained by the timing of fall rains, because soil profiles may be too dry for sowing. In northeastern Oregon, this is typical when sowing into ground that was previously cropped (as opposed to fallowed). For annual cropping systems, rainfall is generally inadequate for seeding until October. In fallowed ground, earlier seeding can be accomplished by using a deep furrow drill to place seeds into moist soil. Growers who plant early (i.e., early September) usually use wider row spacing and lower seeding rates than they would for later plantings to take advantage of the high tillering capacity of early sown wheat (Klepper et al., 1988), and to reduce within-row competition. While early seeded wheat may produce 5 to 6 tillers with heads, late seeded (i.e., late November–early December) plants only produce 2 to 3 tillers with heads (Klepper et al., 1988; Zwer et al., 1995; Rickman et al., 1996).

The objective of this study was to compare response of grain yield, water use, and water-use efficiency of several wheat genotypes to planting treatments that ranged from early fall planting, using deeper planting depth, wider row spaces, and lower seeding rates, to late planting dates, using shallower seeding depth, narrower row spaces, and higher seeding rates.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS NOTES RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Site Characteristics
The study was initiated in the 1997 cropping year (from 1 Sept. 1996 to 31 Aug. 1997) at the Columbia Basin Agricultural Research Center of Oregon State University, Pendleton, OR. The soil at the study site is a Walla Walla silt loam, derived from loess parent material. This soil has a deep (>1.5 m) profile with uniform texture and bulk density, except at the plow pan layer where the bulk density is slightly higher (Allmaras et al., 1977). In the spring of 1995, the experimental field was uniformly seeded with spring wheat to eliminate any residual moisture or fertilizer effects from the previous experiments. After harvest of the spring wheat, the field was summer fallowed to store moisture. Therefore, the experimental field was fairly uniform in terms of texture, fertility, and moisture in 1997. The soil characteristics for the 1998 and 1999 cropping years were similar to 1997, but because summer fallow ground was required for the study, the experimental site had to be moved to different locations on the experiment station each year. These fields were also uniformly seeded with spring wheat and then summer-fallowed before establishing the experiment.

Wheat Cultivars
Four winter wheat cultivars (Stephens, Rohde, Gene, Madsen) and two spring wheat cultivars (Alpowa and ID485) were selected for the study. Two additional winter wheat cultivars (Rod and Temple) were added to the study in 1998 and 1999 cropping years. A short description of each cultivar follows.

Stephens, the industry standard for more than 20 yr, has a high yield potential, but is susceptible to some common diseases that are associated with early planting. Gene has high yield potential but is marginal for winter hardiness and is more susceptible to certain diseases than Stephens. Madsen has fair to good yield potential and is tolerant to common diseases that are associated with early planting. Rod has good yield potential with some disease tolerance, especially for midplanting dates in October. All four cultivars are common soft white wheat. Rohde is a high yielding winter soft white club wheat (Triticum aestivum, vir. compactum Host) that has some disease susceptibility. Temple is a recently released soft white club wheat that has better disease tolerance than Rohde. Alpowa is a soft white spring wheat cultivar, whereas ID485 is an experimental hard red spring wheat (Triticum aestivum L.) cultivar with excellent milling and baking characteristics.

Planting Treatment
Seven planting treatments were chosen for the study. Treatments were as follows:

Treatment 1 was planted in early September using a John Deere¹ (Deere & Co., Moline, IL) HZ Splitpacker plot drill with 0.36-m row spacing and a seeding rate of 194 seeds m^-2. Seeds were planted into 8- to 10-cm furrows with 4- to 5-cm soil cover above the seeds.

Treatment 2 was planted in mid-September using the same drill and seeding rate as Treatment 1.

Treatment 3 was planted in early October using a Hege 55 (Hege Maschinen GmbH, Domane Hohebuch, D-74638 Waldenburg, Germany) plot drill with double disc openers on 0.15-m spacing and a seeding rate of 280 seeds m^-2. Seeds were seeded into shallow furrows (approximately 3 cm) with 4- to 5-cm soil cover above the seeds.

Treatment 4 was planted in late October to early November (depending on weather and field conditions), using the same drill and seeding rate as Treatment 3.

Treatment 5 was planted in late November to early December (depending on weather and field conditions), using the same drill and seeding rate as Treatment 3.

Treatment 6 was planted in mid- to late February, using the same drill and seeding rate as Treatment 3.

Treatment 7 was planted in mid- to late March, using the same drill and seeding rate as Treatment 3.

All seeds were treated with Lindane 30C (gamma isomer of benzene hexachloride) and VITAVAX-THIRAM (carboxin and tetramethylthiuram disulfide) before planting.

Experiment Design
In the 1997 cropping year, four winter wheat cultivars (Stephens, Rohde, Gene, and Madsen) were seeded in all seven planting treatments, and two spring wheat cultivars (Alpowa and ID485) were seeded in Planting Treatments 3 through 7. In 1998 and 1999, two winter wheat cultivars (Rod and Temple) were added to the study and planted in all seven treatments. The planting dates for each year are shown in Table 1.

Wheat grain was harvested using a Hege 140 (Hege Maschinen GmbH, Domane Hohebuch, D-74638 Waldenburg, Germany) plot combine. Harvest date, which was determined by measuring grain moisture content, ranged from mid-July for the first treatment to late August for the last treatment. In the 1998 cropping year, Planting Treatments 1, 2, 3, and 4 were harvested on 17 July 1998, Planting Treatment 5 was harvested on 29 July 1998, Planting Treatment 6 was harvested on 11 Aug. 1998, and Planting Treatment 7 was harvested on 24 Aug. 1998. In the 1998–1999 cropping year, Planting Treatments 1, 2, 3, and 4 were harvested on 28 July 1999, and Planting Treatments 5, 6, and 7 were harvested on 20 Aug. 1999.

Soil Water Measurement
Starting in the 1998 cropping year, soil water content was measured before planting and after harvest to calculate crop ET and water use efficiency. In the 1998 cropping year, neutron probe access tubes were installed at the center of each planting treatment plot, over three replications, containing the cultivars Stephens, Madsen, Temple, Alpowa, and ID485. Plots with the cultivar Temple were not measured in the 1999 cropping year. A CPN 503DR neutron probe (CPN Corp., Pacheco, CA) was used to measure soil water in 0.15-m increments for the first 0.3 m, then in 0.30-m increments down to a 1.5-m depth. The neutron probe was calibrated in the field, and the calibration curve for 0.15 to 1.22 m was:

where CR is the count ratio (count divided by standard count). The standard error of the regression model estimation was 0.009 m³m^-3, and the correlation coefficient was 0.91.

Evapotranspiration (ET) was calculated using the water balance equation:

where S is the cumulative change in soil-stored water between planting and harvest, and P is the cumulative amount of precipitation during the same period. Drainage from the root zone was assumed to be negligible based on the Payne et al. (2001) analysis of 24 yr of neutron probe data, and Chen and Payne's (2001) analysis of unsaturated hydraulic conductivity functions for this soil. Runoff and runon were also assumed to be negligible in the calculation because the plots were on relatively level (<3% slope) ground. However, Payne et al. (2001) speculated that runoff during winter months, due to occasional rains when the ground was frozen (Zuzel, 1994), may have contributed to scatter in the data points around a linear model that related wheat yield to ET.

Mean daily atmospheric water vapor pressure deficit (MDA-VPD) was calculated from daily maximum and minimum air temperatures measured regularly at the Columbia Basin Agricultural Research Center's meteorological station. The MDA-VPD was calculated by averaging the VPD at the daily maximum and minimum temperatures, assuming that the relative humidity was 100% at the daily minimum temperature. The VPD was calculated using equations in Campbell (1977). The growing season mean daily atmospheric water vapor pressure deficit (GSMDA-VPD) was defined as the average daily vapor pressure deficit over the crop growth cycle. It was calculated by dividing the sum of the MDA-VPD over the growing season to the total days of the growing season.

Statistical Analysis
Planting treatment was used in the analysis of variance (ANOVA) despite the fact that it was not randomized in the main plots. The assumption was made that the uniformity of soil conditions at the experimental site, as described earlier, justified this approach for a split plot design.

Because spring wheat cultivars were not used in the first two planting treatments, variances of yield, ET, ET/VPD, and WUE (water-use efficiency = yield/ET) of spring wheat and winter wheat cultivars were analyzed separately. For winter wheat, only those cultivars that were used in all 3 yr were included. To compare winter and spring wheat cultivars, ANOVA was also performed for winter and spring wheat cultivars combined at Planting Treatments 3 through 7. The ANOVA for split-plot design was performed (Montgomery, 1991). Years were assigned to blocks, planting treatments to whole plots, and cultivars to subplots. The whole plot effect (planting treatment) was tested against the whole plot error (Year x Planting treatment), the subplot cultivar effect was tested against Year x Cultivar, and Treatment x Cultivar interaction was tested against the subplot error (Year x Cultivar x Planting treatment). The statistical package SYSTAT 10.2 (SYSTAT Software, Richmond, CA) was used for all ANOVA.

	RESULTS

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Weather
Total precipitation was 550, 396, and 466 mm in the 1997, 1998, and 1999 cropping years, respectively. The distribution patterns were different over 3 yr (Fig. 1), most notably in 1998, when nearly 80 mm of rain fell in May.

View larger version (27K): [in this window] [in a new window]   Fig. 1. Monthly precipitation recorded at the meteorological station at the Columbia Basin Agricultural Research Center for 1997, 1998, and 1999 cropping years.

View larger version (22K): [in this window] [in a new window]   Fig. 2. (a) Mean daily atmospheric water vapor pressure deficit (MDA-VPD) calculated from daily maximum and minimum air temperatures at the Columbia Basin Agricultural Research Center, and (b) growing season mean daily water vapor pressure (GSMDA-VPD) calculated by dividing the sum of MDA-VPD to the days of the growing season. The VPD was calculated using equations in Campbell (1977).

View larger version (61K): [in this window] [in a new window]   Fig. 3. Mean yields of four winter wheat cultivars at seven planting treatments. Data are from 1997, 1998, and 1999 experiments. The error bars in the graphs represent ±1 SE. Bars within each cultivar with same letters above indicate not significantly different based on Fisher's protected LSD (P < 0.1).

Analysis of variance for winter and spring wheat cultivars combined at Planting Treatments 3 through 7 indicates that planting treatment, cultivar, and Planting treatment x Cultivar significantly affected yield (P < 0.05, Table 3). Comparing separate means among cultivars at each planting treatment indicate that spring wheat cultivar Alpowa had higher yield than ID485 at Planting Treatment 3, but both spring wheat cultivars had lower yield than winter wheat cultivars; there was no difference in yield among winter wheat cultivars (Fig. 4). At Planting Treatment 4, Alpowa had similar yield as winter wheat cultivars, but ID485 had lower yield than Alpowa and winter wheat cultivars. At Planting Treatment 5, there was no significant difference among all winter and spring wheat cultivars. At Planting Treatment 6, Alpowa yielded higher than Gene and Madsen and Stephens, but it yielded similarly as Rohde and ID485. At Planting Treatment 7, however, both spring wheat cultivars had greater yield than winter wheat cultivars; and among winter wheat, Rohde had greater yield than Gene and Madsen.

View larger version (62K): [in this window] [in a new window]   Fig. 4. Mean yields of winter and spring wheat cultivars at each planting treatment from 3 through 7. Data are from 1997, 1998, and 1999 experiments. The error bars in the graphs represent ±1 SE. Bars within each planting treatment with same letters above indicate not significantly different based on Fisher's protected LSD (P < 0.05).

Dividing ET by GSMDA-VPD to compensate for seasonal difference in atmospheric demand (Gregory, 1984; Payne et al., 2001) gave different results (Table 2). For winter wheat, planting treatment and cultivar became significant at the P < 0.001 level. The effects of Planting treatment x Cultivar interactions remained insignificant. For spring wheat, the planting treatment became significant at the P < 0.01 level. The effects of cultivar and Planting treatment x Cultivar remained insignificant. Although the difference of ET/VPD between the two winter wheat cultivars was significant, the magnitude of the difference was only 8.6 mm kPa^-1 between Stephens (773.6 mm kPa^-1) and Madsen (782.2 mm kPa^-1). Both winter and spring wheat had approximately 380 to 650 mm kPa^-1 greater ET/VPD (approximately 110–160 mm ET) at the fall seeding dates than at the spring seeding dates. Means of ET/VPD for winter and spring wheat at each planting treatment were displayed in Table 4.

	DISCUSSION

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Winter wheat had the greatest yield at the October planting treatments, after which yield decreased with delayed seeding dates. The degree of yield decline may depend on weather conditions of the year and selection of cultivars. These different yield responses to planting treatments for winter wheat cultivars were observed in 1997, 1998, and 1998, which was probably related to spring rainfall (Fig. 1). Water supply patterns have been observed to be as important to yield as the total amount of water supplied, where optimal yield is produced when the water supply pattern matches plant growth and water demand (Passioura, 1983; Loss and Siddique, 1994). Rasmussen et al. (1998) analyzed the historical long-term experiments in Pendleton, OR, and found that wheat yield was generally greater if rain was partially distributed during the spring months, particularly in May and June. Decrease of winter wheat yield with delayed seeding dates was also reported in Canada and the Upper Midwest of the USA (Fowler, 1983; Dahlke et al., 1993). However, the two September planting treatments in this study yielded lower than the early October planting treatment, which was especially significant for Stephens and Gene. The reason for the lower yields in September was not clear due to the confounding effects of planting date, row spacing, and drill type. Using wider row spacing and lower seeding rate for early planting is a common practice for growers in the area. Dahlke et al. (1993) suggested that seeding rate should be adjusted depending on planting date and genotype in the Upper Midwest of the USA. They found that yield for late September seeding can be increased to the comparable level as early September seeding by increasing seeding rate for the late seeding date.

Disease is another factor that could greatly reduce wheat yield in early planting. Some diseases, such as Fusarium foot rot caused by Fusarium pseudograminearum and F. culmorum, strawbreaker foot rot caused by Pseudocercosporella herpotrichoides, Cephalosporium strip caused by Cephalosporium gramineum, and barley yellow dwarf (a viral disease) are most damaging when winter wheat is seeded early in the fall between late August and mid-September (Ogg et al., 1999; Smiley, 1996). In this study, September plantings were observed to have higher overall disease severity ratings than did later plantings. The percentage of tillers of Stephens affected by Fusarium foot rot tended to be higher in September than those of the October plantings (data not shown). Further studies are needed to identify the primary causes of low wheat yield in September plantings.

With cold hardiness cultivars, such as Alpowa, fall-seeded crops could produce similar yields as spring-seeded ones. With frost-sensitive cultivars, a cold winter could result in greater winter kill and substantial yield loss. For both cultivars, the late November–planted spring wheat in this study produced equivalent yields to the spring-planted wheat (Fig. 4). The late November–seeded spring wheat was a dormant seeding and generally did not germinate until early spring. This dormant seeding could avoid winter seedling kill and take advantage of good soil moisture in the early spring, and therefore, should be considered as an alternative practice in the region.

Figure 5 shows that, for the same grain yield levels, spring-seeded wheat had a greater WUE than fall-seeded wheat. Warmer temperatures in the spring may have permitted more rapid canopy closure in comparison to fall months, coupled with increasingly infrequent rainfall in the spring, resulted in less frequent periods during which the soil surface was wet. Therefore, more water may have been used through transpiration by plant than through soil surface evaporation. In other words, the ratio of transpiration to evaporation may have been greater for the spring-planted wheat than the fall-planted wheat. The WUE data for spring seeded wheat in two cropping years (1998 and 1999) agreed well. However, over the same two cropping years, WUE for fall-seeded wheat fell into two different lines (Fig. 5). Comparing Fig. 5 with Fig. 1, it seemed that with more precipitation distributed in the fall in 1999 than in 1998 (total 466 mm in 1999 and 352.6 mm between September and March; total of 396 mm in 1998 and 263.1 mm between September and March), a lower slope of WUE vs. yield was produced in Fig. 5, indicating less efficient use of water in 1999 fall-seeded crops. However, the soil surface evaporation and leaf area index were not measured in this study. More data on leaf area and evaporation from the soil surface would help clarify this response. Comparison of WUE for spring and winter cultivars in northeastern Oregon merits further study, in our view, because yield gains for spring wheat have been greater than those of winter wheat in recent years (Payne et al., 1997), and spring wheat cropping systems hold distinct advantages in terms of soil conservation (Pikul et al., 1993; Payne et al., 2001).

View larger version (30K): [in this window] [in a new window]   Fig. 5. Plots of water-use efficiency vs. yield for fall-seeded (triangles) and spring-seeded (circles) in 1998 (solid symbols) and 1999 (open symbols).

	CONCLUSIONS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS NOTES RESULTS DISCUSSION CONCLUSIONS REFERENCES

	ACKNOWLEDGMENTS

 
The authors thank Karl Rhinhart and Lisa Patterson for their help in field planting and laboratory disease evaluations. Funding for this study was provided by Oregon Wheat Commission and Oregon Agricultural Research Foundation.

	NOTES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS NOTES RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
¹ Mention of a trademark does not constitute an endorsement.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS NOTES RESULTS DISCUSSION CONCLUSIONS REFERENCES

 

• Allmaras, R.R., R.W. Rickman, L.G. Ekin, and B.A. Kimball. 1977. Chiseling influences on soil hydraulic properties. Soil Sci. Soc. Am. J. 41:796–803.[Abstract/Free Full Text]
• Anderson, W.K., and W. Smith. 1990. Yield advantage of two semi-dwarf compared with two tall wheats depending on sowing time. Aust. J. Exp. Agric. 30:607–614.
• Campbell, G.S. 1977. An introduction to environmental biophysics. Springer-Verlag, New York.
• Chen, C., and W.A. Payne. 2001. Measured and modeled hydraulic conductivity of a Walla Walla silt loam. Soil Sci. Soc. Am. J. 65:1385–1391.[Abstract/Free Full Text]
• Connor, D.J., S. Theiveyanathan, and G.M. Rimmington. 1992. Development, growth, water-use and yield of a spring and a winter wheat in response to time of sowing. Aust. J. Agric. Res. 43:493–516.
• Coventry, D.R., T.G. Reeves, H.D. Brooke, and D.K. Gann. 1993. Influence of genotype, sowing date, and seeding rate on wheat development and yield. Aust. J. Exp. Agric. 33:751–757.
• Dahlke, B.J., E.S. Oplinger, J.M. Gaska, and M.J. Martinka. 1993. Influence of planting date and seeding rate on winter wheat grain yield and yield components. J. Prod. Agric. 6:408–414.
• Fischer, R.A. 1979. Growth and water limitation to dryland wheat yield in Australia: A physiological framework. J. Aust. Inst. Agric. Sci. 45:83–94.
• Fowler, D.B. 1983. Influence of date of seeding on yield and other agronomic characters of winter wheat and rye grown in Saskatchewan. Can. J. Plant Sci. 63:109–113.
• Gregory, P.J. 1984. Water availability and crop growth in arid regions. Outlook Agric. 13:208–215.
• Kerr, N., K.H.M. Siddique, and R.J. Delane. 1992. Early sowing with wheat cultivars of suitable maturity increases grain yield of spring wheat in a short season environment. Aust. J. Exp. Agric. 32:717–733.
• Klepper, B., R.W. Rickman, J.F. Zuzel, and S.E. Waldman. 1988. Use of growing degree days to project sample dates for cereal crops. Agron. J. 80:850–852.[Abstract/Free Full Text]
• Leggett, G.E. 1959. Relationships between wheat yield, available moisture, and available nitrogen in eastern Washington dryland areas. Wash. Agric. Exp. Stn. Bull. 609. Washington State Univ., Pullman, WA.
• Loss, S.P., and K.H.M. Siddique. 1994. Morphological and physiological traits associated with wheat yield increases in Mediterranean environments. Adv. Agron. 52:229–276.
• Montgomery, D.C. 1991. Design and analysis of experiments. John Wiley & Sons, New York.
• Ogg, A.G., Jr., R.W. Smiley, K.S. Pike, J.P. McCaffrey, D.C. Thill, and S.S. Quisenberry. 1999. Integrated pest management for conservation systems. p. 97–128. In E.L. Michalson et al. (ed.) Advances in conservation farming. CRC Press, Boca Raton, LA.
• Passioura, J.B. 1983. Roots and drought resistance. Agric. Water Manage. 7:265–280.
• Payne, W.A., P.E. Rasmussen, C. Chen, and R.E. Ramig. 2001. Assessing simple wheat and pea models using data from a long-term tillage experiment. Agron. J. 93:250–260.[Abstract/Free Full Text]
• Payne, W.A., P.E. Rasmussen, and R. Goller. 1997. Major Factors influencing wheat yield improvement during the last thirty years. p. 43–46. In 1997 Columbia Basin Agricultural Research Annual Report. Spec. Rep. 977. Agric. Exp. Stn., Oregon State Univ. (in cooperation with USDA-ARS), Corvallis, OR.
• Pikul, J.L., R.E. Ramig, and D.E. Wilkins. 1993. Soil properties and crop yield among four tillage systems in a wheat–pea rotation. Soil Tillage Res. 26:151–162.
• Rasmussen, P.E., W.A. Payne, and R.H. Goller. 1998. Thirty-year rainfall trends and implications for crop yield in the Columbia Plateau. Columbia Basin Agric. Res. Spec. Rep. 989. Oregon State Univ., Corvallis, OR.
• Rickman, R.W., S.E. Waldman, and B. Klepper. 1996. MODWht3: A development-driven wheat growth simulation. Agron. J. 88:176–185.[Abstract/Free Full Text]
• Smiley, R.W. 1996. Diseases of wheat and barley in conservation cropping systems of the semi-arid Pacific Northwest. Am. J. Alternative Agric. 11:95–103.
• Stapper, M., and H.C. Harris. 1989. Assessing the productivity of wheat genotypes in a Mediterranean climate, using a crop simulation model. Field Crops Res. 20:129–152.
• Zuzel, J.F. 1994. Runoff and soil erosion phenomena in the dryland grain growing region of the Pacific Northwest. USA. Trends Hydrol. 1:209–216.
• Zwer, P.K., A. Sombrero, R.W. Rickman, and B. Klepper. 1995. Club and common wheat yield component and spike development in the Pacific Northwest. Crop Sci. 35:1590–1597.[Abstract/Free Full Text]

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