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1998 STEEP III Progress ReportRESEARCH PROJECT TITLE: Modified Wheat-Potato Rotations to Reduce Wind Erosion INVESTIGATORS: Charlotte Eberlein, UI; Edward Souza, UI; Larry Robertson, UI; Paul Patterson, UI PROJECT OBJECTIVES:
KEY WORDS: wheat-potato rotations, weeds, wind erosion STATEMENT OF PROBLEM: In southern Idaho, producers generally rotate from potatoes to spring wheat or barley, which leaves fields bare over the winter and subject to wind and water erosion. Other options for wheat production following potatoes need to be evaluated, including late-seeded winter wheat and dormant-seeded spring wheat. These seeding practices should be compared with a standard spring wheat seeding for winter and spring soil cover, stand, weed suppression, and yield. ZONE OF INTEREST: Irrigated potato growing areas of southern Idaho; grain-potato, grain-grain-potato rotations. ABSTRACT OF RESEARCH FINDINGS: Alternatives to conventional spring wheat seeding practices in a potato-grain rotation were evaluated in on-station trials at the Aberdeen Research and Extension Center and in on-farm trials in growers’ fields. Winter wheat seeded after potato harvest was compared with dormant-seeded spring wheat for ground cover, yield, and weed suppression. In on-station trials, winter wheat was planted Oct. 12 and dormant-seeded spring wheat was planted Oct. 22. Winter- and dormant-seeded spring wheat had similar yield and test weight. In on-farm trials, winter wheat and dormant-seeded spring wheat were planted on Oct. 16 at one farm and on Nov. 2 at a second farm. At both on-farm locations, dormant-seeded Treasure spring wheat had higher yield and test weight than late-seeded Malcolm winter wheat. No clear effects of wheat seeding practice on weed management were observed. RESULTS AND INTERPRETATION: Soil erosion is a significant problem following potato harvest. In southern Idaho, producers generally rotate from potatoes to spring wheat or barley, which leaves fields bare over the winter. One option for reducing wind erosion is to plant winter wheat after potato harvest. However, several factors limit winter wheat planting. The optimum time for seeding winter wheat is Sept. 15 to Oct. 1. Potato harvest typically begins about Sept. 20 and lasts until about Oct. 10, so waiting until potato harvest is complete puts wheat planting outside the optimum window for stand establishment. During potato harvest, producers face a shortage of equipment/labor for seeding winter wheat. Dormant-seeded spring wheat may give growers an option beyond the optimum planting time for winter wheat. Dormant-seeded spring wheat is planted in late October or early November, after it is too cool for wheat emergence, but before the ground freezes. The seed lies dormant in the soil until it germinates and begins to grow in late winter/early spring, generally before producers could begin working fields for a spring planting. Moreover, dormant seeding eliminates the need for soil disturbance in early spring when wind storms are frequent. To evaluate alternatives to conventional spring wheat seeding practices, late-seeded winter wheat and dormant-seeded spring wheat were compared with conventional spring wheat planting practices in field trials at the Aberdeen Research and Extension Center near Aberdeen, ID. Three on-farm comparisons of late-seeded winter wheat vs. dormant-seeded spring wheat also were conducted with cooperators at Krown Farms and R&J Farms near Aberdeen, ID. Aberdeen Research and Extension Center (AREC) Trial. Wheat was seeded with a commercial grain drill at 100 lb/a with 7-inch row spacing. ‘Malcolm’ winter wheat (WW) was seeded on Oct. 10, 1997; ‘Treasure’ spring wheat was dormant-seeded on Oct. 22, 1997; and ‘Penewawa’ spring wheat (SW) was seeded on March 31, 1998. The experimental area was naturally infested with common lambsquarters, hairy nightshade, prostrate knotweed, wild buckwheat, and common mallow. Bromoxynil + MCPA (Bronate) was applied at 1.5 pt/a to herbicide-treated subplots on May 5, 1998. Untreated subplots were used to measure effects of wheat seeding practices on weeds. Stand establishment and winter survival of fall-planted winter wheat and dormant-seeded spring (DSS) wheat were excellent. Wheat density in Malcolm WW and Treasure DSS plots on April 13 was 23 and 22 plants per square foot, respectively. On May 12, Penewawa plant density was 25 plants per square foot. Light interception measurements demonstrated that Malcolm WW developed canopy closure more rapidly than Treasure DSS, which developed canopy closure more rapidly than Penewawa SW (Table 1). Wheat development as measured by Feeke’s stage is shown in Figure 1. Malcolm WW developed slightly ahead of Treasure DSS until the May 12 evaluation, from which point the two cultivars were similar. Both Malcolm WW and Treasure DSS developed ahead of Penewawa SW. Table 1. Light interception by wheat canopy in AREC study.
April, May, and June were unusually cool, which provided a long period of vegetative growth and extensive tillering (Figure 2). Malcolm, Treasure, and Penewawa had 77, 68, and 59 tillers per square foot, respectively, on July 20 (Table 2). However, unusually warm weather in July (Figure 2) caused significant embryo abortion and reduction in test weight. Grain yields for Malcolm, Treasure, and Penewawa were 99, 96, and 86 bu/ac, respectively, and test weights were 58, 58 and 57 lb/bu, respectively (Table 2).
Figure 1. Wheat development in the AREC trial.
Figure 2. Mean daily air temperatures at Aberdeen in 1998 compared to the 7-year average.
Table 2. Wheat tiller density, grain yield, and test weight at AREC.
a Means within a column followed by the same letter were not significantly different according to an LSD test at the 95% confidence interval. The major weed species infesting the plots were common lambsquarters, hairy nightshade, and redroot pigweed. Weed density was monitored regularly from Apr. 20 to May 26 (Figure 3). Weed dry matter and density also were sampled on July 20. On May 26, total weed density in untreated areas was less in Malcolm WW plots than in Treasure DSS or Penewawa SW plots. Wheat grew well during the long vegetative period in June and was highly competitive with weeds. Total weed density on July 20 was very low and was less in Malcolm WW plots than in Penewawa SW plots. Total weed dry matter also was very low and was significantly less in Malcolm WW and Treasure DSS plots than in Penewawa SW plots (Table 3). Grain yields were similar in herbicide-treated and untreated subplots, indicating that weeds infesting the untreated areas did not affect grain yield. Table 3. Total weed density and dry matter in untreated areas on July 20.
a Means within a column followed by the same letter were not significantly different according to an LSD test at the 95% confidence interval. Figure 3. Density of weeds in untreated plot areas in the AREC trial from April 20 through May 26.
On-farm trials. On-farm trials were conducted in cooperation with Krown Farms and R&J Farms. At Krown Farms, Treasure spring wheat and Malcolm winter wheat were seeded into a well-prepared seed-bed with a forced-air planter equipped with a shank planting shoe on Oct. 16. Emergence of both Treasure and Malcolm at Krown Farms was excellent. On November 5, 1997, wheat was emerged, approximately 0.5 inches tall, and provided 1% ground cover. By November 10, wheat was 1 inch tall and provided 5% ground cover. On Jan. 7, 1998, Treasure plots provided 5% ground cover, while Malcolm plots had 2% ground cover. On Feb. 6, 1998, both treatments had 5% ground cover. By March 16 ground cover was 20 to 25% for both treatments. Stand percentages for Malcolm and Treasure were estimated to be 98% and 93%, respectively. Ground cover for both treatments was 54 to 55% on April 22. Malcolm and Treasure developed similarly through the vegetative growth phase (Figure 4). Light interception by the wheat canopy was similar for both cultivars (Table 4). Treasure yielded 75 bu/ac, 13% above Malcolm (67 bu/ac), and Treasure had a 61 lb/bu test weight, which was 3 lb/bu better than Malcolm (58 lb/bu). Table 4. Light interception by Malcolm winter wheat and Treasure dormant-seeded spring wheat canopies at Krown Farms.
Figure 4. Feeke's stages of wheat development for Malcolm winter wheat and Treasure dormant-seeded spring wheat at Krown Farms from March 16 to May 27.
Weed populations at Krown Farms were low. Total weed density on May 5 was 0.4 weeds per square foot in both the Malcolm and Treasure treatments. Lambsquarters and hairy nightshade were the predominant weeds in the field. The grower’s standard herbicide practice provided excellent weed control. Two general observations about the trial at Krown Farms should be noted. Several low-lying areas of the field had standing water for some time in late February. In these areas, Treasure stand was reduced more significantly than Malcolm stand. A severe hailstorm passed through the experimental area on June 25, after the wheat had headed. The hailstorm significantly damaged the experimental area. Some lodging was observed in the experimental area, and more lodging was observed in Treasure plots than in Malcolm plots. At R&J Farms, wheat was seeded into a well-prepared seed-bed with a conventional drill on Nov. 2. Emergence of both Treasure and Malcolm at R&J Farms was fair. Two strip trials were established with four replications per trial.
As at Krown Farms, light interception by the two wheat cultivars was similar, reaching >90% interception by June 5 (Figure 5). Wheat development as measured by Feeke’s stages was not significantly different between the two varieties, and closely followed the pattern observed at Krown Farms. Figure 5. Light interception by Malcolm winter wheat and Treasure dormant-seeded spring wheat seeded Nov. 2 at R&J Farms.
On April 28, weed populations at R&J Farms Site I were 1.1 wild buckwheat and 1.1 common lambsquarters per square foot in Treasure plots, and 2.4 wild buckwheat and 1.8 common lambsquarters per square foot in Malcolm plots. On May 8, weed populations at R&J Farms Site II were 0.1 wild buckwheat, 1.9 common lambsquarters, and 0.4 Canada thistle per square foot in Treasure plots, and 0.2 wild buckwheat, 1.7 common lambsquarters, and 0.3 Canada thistle per square foot in Malcolm plots. Weed densities were not significantly different for the two treatments. The grower-applied broadleaf herbicide application provided fair to good control of common lambsquarters and wild buckwheat, and poor to fair control of Canada thistle. Both fields at R&J farms were in the path of the severe hailstorm that had damaged the trial at Krown farms. The unusually warm July temperatures caused significant embryo abortion. At harvest, heads of both cultivars generally lacked tertiary kernels, and often lacked secondary kernels. Analysis of variance indicated that the cultivars performed similarly at both locations, therefore the two locations were combined for analysis. In the combined analysis, the cultivars differed significantly for both yield and test weight, with Treasure yielding 13 bu/ac more than Malcolm and having 6 lb/bu better test weight than Malcolm. Table 5. Yield and test weight at R&J Farms. Data were averaged over test sites at R&J Farms.
a Means within a column followed by the same letter were not significantly different according to an LSD test at the 95% confidence interval. Summary. At the Aberdeen Research and Extension Center, Malcolm WW was planted twelve days earlier than Treasure DSS wheat. Malcolm WW emerged earlier and had more growth going into the winter than Treasure DSS. Treasure DSS lagged behind Malcolm WW in development through mid-May. However, at harvest, Malcolm WW and Treasure DSS had similar yields and test weights. Both Malcolm WW and Treasure DSS outyielded and had better test weight than Penewawa SW. On May 26, weed densities in untreated plot areas were lower in Malcolm WW plots than in Treasure DSS and Penewawa SW plots. However, all wheats competed effectively with emerged weeds. Weed biomass in untreated check areas in late July was lower in Malcolm WW and Treasure DSS than in Penewawa SW plots. In on-farm tests, Malcolm WW and Treasure DSS were planted on the same dates, emerged similarly, and developed similarly. No differences in weed emergence were observed. Treasure significantly outyielded Malcolm at Krown Farms and R&J Farms and had significantly higher test weight at both locations. These results indicate that, at a given planting date and in the absence of stand-reducing winter conditions, dormant-seeding Treasure may offer significant advantages to producers in terms of test weight and/or yield compared to late-seeded winter wheat. No clear advantages in weed management were observed with dormant-seeded spring wheat compared to late-seeded winter wheat. INTERACTION (COOPERATION) WITH OTHER SCIENTISTS CONDUCTING RELATED ACTIVITY: None. PUBLICATION AND PRESENTATIONS: No publications to date. Field plots were shown at the Potato Weed Science Field Day on June 25, 1998, at Aberdeen, ID. |
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