Influence of Raised Beds, Row Spacing and Seeding Rate on Production of Wheat on Alluvial Soil

Linda Benedict, Arceneaux, Kelly J., Mascagni, Jr., Henry J., Bell, Robert L., Harrison, Stephen A.  |  3/4/2010 10:41:46 PM

Early February wheat yield plots showing staked areas for stand counts with 7-inch and 14-inch row spacings.(Photo by Steve Harrison)

Table 2.

Table 1.

Table 3.

Rick Mascagni, Steve Harrison, Kelly Arceneaux and Bubba Bell

Wheat acreage fluctuates widely from year to year, primarily because of grain and fertilizer prices and weather patterns affecting planting and harvest. Marketing small grains in late spring when wheat is harvested provides growers with much-needed cash flow to cover the costs of production of summer crops such as soybeans. Management practices, particularly drainage, are very important in maximizing yield and profitability.

The use of raised beds for wheat production facilitates double-cropping with soybeans and should provide better drainage for the wheat crop. Some Louisiana soybean growers are using wide beds (72-80 inches) with 15- to 16- inch drilled rows for soybean production. These wide beds work well for a variety of crops, including cotton, soybean and sugarcane. Wide beds offer significant advantages in controlling soil moisture, both irrigation and drainage, and are amendable to narrow row spacing.

A wide-bed cropping system that includes wheat in the winter would increase flexibility and offer rotational advantages, particularly if the soybean planter can be used to plant wheat. Row spacing of 15-16 inches – wider than the conventional 7- to 10-inch spacing – has been shown to reduce wheat yield slightly in Ohio. Because wheat in Louisiana continues to grow and produce tillers – or additional plant shoots – all winter the crop may be able to compensate for wider rows without significant yield loss. An additional concern is whether or not seeding rates should be adjusted with wide rows, which may offer additional savings to growers. Wider row spacing for wheat may improve planting efficiency for a double- crop such as soybeans.

This study was designed to evaluate the influence of raised versus flat seedbeds, conventional (7-inch) versus wide row spacing (14-inch) and normal versus reduced seeding rate on yield performance of five wheat varieties produced on an alluvial Mississippi River soil.

Field experiments were conducted in 2006-07, 2007-08 and 2008-09 on Tunica silty clay at the Northeast Research Station near St. Joseph. Seedbed treatments were the conventional flat seedbed and 80-inch-wide, raised beds. Rows were spaced at 7 inches and 14 inches. A small-grain plot planter was used for planting. Seeding rates were 12 and 24 seeds per square foot – approximately equivalent to a seeding rate of 47 or 94 pounds of seed per acre – averaged across the five varieties. The adapted varieties AGS 2060, AgriPro Coker (AC) 9553, Delta King (DK) GR9108, Pioneer brand (PB) 26R61 and Terral LA841, which differ in tillering ability, were evaluated across row spacings, seeding rates and bed types. Tillers per plant were determined by comparing the number of seedlings with the final number of grain heads. Grain yield at 13 percent moisture was determined by harvesting complete plots with a small-plot combine.

Average yields across all treatments ranged from 52.6 bushels per acre in 2008 to 70.7 bushels per acre in 2009 (Table 1). There were no yield differences between wheat grown on raised beds and wheat grown without beds when averaged across years and combinations of seeding rates and varieties. In 2007, the flat system significantly out-yielded the bed system, whereas the raised bed system was significantly better in 2009, a year with excessive rainfall during winter tillering (November-December 2008). Total rainfall for the months of October through May ranged from 35.0 inches for 2006-07 to 42.8 inches for 2008- 09. Rainfall was excessive in the fall of 2008, totaling 18.9 inches in November and December, and raised beds produced higher yields as a result. Averaged across the three years, yields were 62.4 bushels per acre for the conventional, flat seedbed and 62.2 bushels per acre for the raised, wide beds. Although the soil evaluated in this study had poor internal drainage, surface drainage was adequate, and water did not pool after a rainfall in any year of the trials.

Average yields ranged from 60.6 bushels per acre for AC 9553 to 65.1 bushels per acre for AGS 2060 (Table 2).

Across years, AGS 2060 was the most consistent high-yielder, while DK GR9108 had the lowest yield. Grain yields in wide rows were equal to those in narrow rows. This indicates that in Louisiana, wheat appears able to compensate for wide spacing, and growers should be able to plant wheat using soybean planters without significant yield reductions, assuming that weed control and fertility levels are adequate to permit plant tillering.

The five wheat varieties generally responded similarly to different row spacings, although some differences in some combinations occurred in 2009. In 2009, PB 26R61 had higher yield for the 14-inch spacing, while yield differences between spacing treatments for the other four varieties were small. The effect of row spacing on the number of tillers depended on year. In 2007, tillers per plant for the low seeding rate was 27 percent higher on the narrow versus the wide row, while tillers were 15 percent lower on the narrow row with the high seeding rate. In 2008, row spacing did not affect tiller numbers for either seeding rate.

The influence of seeding rate and row spacing, averaged over seedbed and variety combinations, on wheat yield is shown in Table 3. Yields were increased only by 2.6 percent with the high seeding rate of 24 seeds per square foot, averaged across trials and row spacing. For the wide row spacing, yields were slightly higher for the 24- versus 12-seeds-persquare- foot rates. Yield differences between seeding rates for the narrow row were small.

This study indicates that advantages of raised beds on soils with good surface drainage are probably minimal, but raised seedbeds can increase wheat yield when excess rainfall occurs during tillering. Additionally, yields for the wide, 14-inch row spacing were equal to yields for the conventional, 7-inch spacing. This implies that growers can use soybean planters to plant wheat, which saves money on equipment costs and improves efficiency of planting a follow-up crop such as soybean without decreasing wheat yields.

Rick Mascagni, Professor, Northeast Research Station, St. Joseph, La.; Steve Harrison, Professor, and Kelly Arceneaux, Research Associate, School of Plant, Environmental & Soil Sciences, LSU AgCenter, Baton Rouge, La.; Bubba Bell, Research Associate, Sweet Potato Research Station, Chase, La.

(This article was published in the winter 2010 issue of Louisiana Agriculture.)

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