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Wheat stubble height affects no-till row crop yields

Source: Steve Watson, Kansas State University | October 3, 2011

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Producers using a no-till wheat/row crop/fallow rotation may find that row crop yields in such a rotation are higher (in years with relatively normal weather) when the wheat stubble height is taller. K-State research in western Kansas by Lucas Haag, Agronomy graduate student, and Alan Schlegel, Agronomist-In-Charge at the Southwest Research-Extension Center-Tribune, has found that corn grain yields increased as stubble height increased. Grain sorghum yield response to stubble height was less apparent, but exhibited a response to moderately higher cutting heights.

Wheat residue provides numerous benefits, including evaporation suppression, delayed weed growth, improved capture of winter snowfall, and reduced soil erosion. Stubble height affects wind velocity profile, surface radiation interception, and surface temperatures, all of which will reduce evaporation potential and increase winter snow catch. Taller wheat stubble is also beneficial to pheasants in postharvest and overwinter fallow periods.

Using stripper headers provides taller wheat stubble than previously attainable with conventional headers. In theory, increasing wheat cutting heights or using a stripper header should further improve the effectiveness of standing wheat stubble. The purpose of our research was to evaluate the actual effect of wheat stubble height on subsequent summer row crop yields.

Procedures

Studies were conducted from 2007 through 2010 at the Southwest Research-Extension

Center dryland station near Tribune. Corn and grain sorghum were planted into standing wheat stubble of three heights: short, optimal, and stripped.

* The short cut treatment was half of optimal cutter bar height.

* Optimal cutter bar height is the height necessary to maximize both grain harvested and standing stubble remaining (typically two-thirds of total plant height).

* The third treatment was stubble remaining after stripper header harvest.

In 2007, these heights were 7, 14, and 22 inches. In 2008, heights of 10, 20, and 30 inches were obtained. In 2009 the heights were 7, 14, and 23 inches. In 2010 the stubble measured 8, 16, and 25 inches. Corn was seeded at the rate of 15,000 seeds per acre, and grain sorghum was seeded at the rate of 33,000 seeds/acre. In 2010 the sorghum plots were split and an additional seeding rate of 41,000 seeds/a was added to the study. Nitrogen was applied to all plots at a rate of 80 to 100 lb/acre. Starter fertilizer (10-34-0) was applied in-row at rates of 7 and 9 gal/a for corn and sorghum, respectively. Plots measured 40 ft × 60 ft. Soil water measurements were obtained by neutron attenuation to a depth of 6 feet in 1-foot increments at seeding and harvest to determine water use and water use efficiency (WUE).

Results: 2007-2010

Over the 4 years 2007-2010, corn grain yield increased from 80 to 92 bu/acre as stubble height increased. Increased grain yields are the result of the effect of stubble height on one primary yield component, kernels per ear, which increased with increasing stubble height from 467 for the low cut to 521 for the stripped stubble treatment. Another key yield component, ear population, also increased numerically with increasing stubble height, suggesting that increasing stubble height also may reduce in-season plant mortality and ear abortion.

Corn grown in stripped or optimal-cutter-bar-height stubble resulted in higher WUE, which increased from 305 lb/inch in short-cut stubble to 361 lb/inch in the stripped stubble treatment.

Over the 4 years, sorghum grain yields exhibited a quadratic response to stubble height, with optimal-cutter-bar-height stubble producing grain yields 4 to 5 bu/acre higher than either the stripped or short-cut treatment. An examination of yield components revealed that kernels per head generally increased with increasing stubble height. Although no statistical differences were observed, heads per plant exhibited a positive response to increasing stubble height. Future efforts in this study will involve more emphasis on yield components, specifically tillers per plant, in an effort to identify any interaction between tillering and the production environment created by stripped stubble.

Data from prior years suggested that sorghum planted into stripped stubble was yielding less than sorghum planted into optimal-cutter-bar-height stubble due to reduced tillering. The addition of the 41,000 seeding rate was designed to further investigate this possibility. Interestingly, in 2010 the increased seeding rate resulted in only a very small increase in plant and head population.

Corn response to wheat stubble height: 2007-2010
Stubble height	Yield (bu/acre)	Plant population (plants/acre)	Ear population (ears/acre)	Kernel weight (oz/1,000)	Kernels per ear	Water use efficiency (lb/inch)
Low	80.3b	15,500	15,100	10.33	467b	305b
Optimal (high) cutter bar height	89.9a	15,400	15,400	10.54	504a	350a
Stripped	92.0a	15,500	15,700	10.42	521a	361a

Grain Sorghum response to wheat stubble height: 2007-2010
Stubble height	Yield (bu/acre)	Plant population (plants/acre)	Head population (heads/acre)	Kernel weight (oz/1,000)	Kernels per head	Water use efficiency (lb/inch)
Low	102.9	19,200	50,200	0.91	2073	413
Optimal (high) cutter bar height	107.4	18,900	51,900	0.92	2069	432
Stripped	101.9	18,300	50,000	0.88	2109	419

Conclusions

Increasing stubble height has improved subsequent corn grain yields and WUE. The impact of stubble height on grain sorghum yields is less apparent at this time and requires further study.

Surprisingly, this study has found little impact of stubble height on profile available soil water. This is in direct contrast to other studies and anecdotal field observations. Corn grain yield differences in the absence of differences in available soil water at planting indicate a more pronounced impact of stubble harvest height on in-season plant-water dynamics than previously thought.

Additional years of observation are needed to identify any potential effect of stubble height on the yield components of grain sorghum and to provide a more robust dataset across multiple years in which to evaluate the effects of stubble height on soil water storage.

Adapted from K-State Southwest Research-Extension Center Field Day 2011, SRP-1052, pages 37-42, available at your local county Extension office, or at: http://www.ksre.ksu.edu/library/crpsl2/srp1052.pdf

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