Long Term Tillage Effects on Grain Yield and Soil Properties in a Soybean/Grain Sorghum Rotation

Abstract

In Nebraska, early adopters of conservation tillage, especially those using no‐till planting, had some concerns regarding planter performance, early season weed control, and possible yield reductions. Selected tillage and planting systems were used long term to evaluate effects on soybean [ Glycine max (L.) Merr.] and grain sorghum [ Sorghum bicolor (L.) Moench] yield, soil properties, and residue cover in a nonirrigated rotation. The six tillage and planting systems selected for evaluation were: no‐till, no‐till with row‐crop cultivation, disk, double disk, chisel, and plow. In 1981, two sets of field plots were established near Lincoln, NE, on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudolls) so that both crops could be evaluated each year. Measurements were not taken until completion of one crop rotation cycle. After this cycle, for the first 3 yr of yield measurements, no differences occurred in grain yield among the tillage and planting systems. After five additional years, differences in yield were measured, with no‐till tending to have the greatest yield for both crops. Row‐crop cultivation of no‐till soybean did not result in any measurable yield differences, but for grain sorghum, row‐crop cultivation resulted in an average yield decrease of 6 bu/acre. Soil organic matter tended to be greatest for the continuous no‐till system and lowest for the plow system. The plow system had slightly less penetration resistance within the 4‐ to 8‐in. depth than the other treatments, whereas, the double‐disk system was slightly greater within the 2‐ to 6‐in. depth. Draft and power requirements for planting in the selected tillage and planting systems were not different The major difference among the tillage and planting systems was residue cover remaining after planting. No‐till had the most residue cover, but there was no appreciable accumulation of residue over the 10 yr of continuous use of the tillage and planting systems. For the last 5 yr, no‐till tended to have the greatest yield for both crops. Thus, for the soil and conditions evaluated, no‐till yields were as good as the other systems during early years, and were better after 5 yr of continuous use. Thus, producers adopting no‐till and other residue management practices have the opportunity to enhance profitability because of the same or greater yields and reduced production costs by eliminating tillage operations. Research Question Early adopters of conservation tillage, especially those using no‐till planting, had concerns regarding planter performance, weed control, and possible yield reductions. Six tillage and planting systems were used in a long term study to evaluate effects of tillage on soybean and grain sorghum yields, soil properties, and residue cover in a nonirrigated rotation. Literature Summary Tillage and planting systems that leave a protective cover of crop residue on the soil surface have been shown to reduce soil losses, and are among the least costly erosion control practices. Few tillage and planting studies have reported on crop production from soybean and grain sorghum rotation. In Nebraska, interest in conservation tillage and other reduced tillage systems began to increase in the early 1980s. Research results concerning conservation tillage were often conflicting and varied depending on production management, rainfall, geographic location, and study duration. Information was available to address concerns for reduced tillage corn production in semi‐humid areas similar to Nebraska. However, limited information was available for soybean and grain sorghum. Therefore, the effect of reduced tillage on soybean and grain sorghum production in a nonirrigated rotation was evaluated. Study Description Six tillage and planting systems in a soybean and grain sorghum rotation were evaluated: no‐till, no‐till with row‐crop cultivation, disk, double‐disk, chisel, and plow. The soil type was a Sharpsburg silty clay loam. Full sized field equipment (6‐row) was used throughout the project. Two sets of plots, one for each crop, were randomized and replicated three times within each set. Operations within each tillage and planting system are listed in Table . Unless otherwise noted, all field operations were performed in the spring. This study's yield observations were taken over 8 yr, ending 10 yr after plot establishment in 1981. Observations on soil properties and crop residue were made once near the end of the 10 yr. In a given year, the same preplant applied herbicide program was used on all tillage and planting systems for each crop. Atrazine and Dual were used for grain sorghum and Sencor and Dual or Prowl were used for soybean. Total herbicide application rate was usually at or below suggested label rates for tilled soils. No burndown herbicide, other than 2,4‐D, was used. Applied Question What effect do tillage and planting systems have on soybean and grain sorghum yields, soil properties, and residue cover when grown in a nonirrigated rotation in southeast Nebraska? After 5 yr of continuous use of the selected tillage and planting systems, several differences in crop yield were measured (Table ). From 1986 through 1990, either one or both of the no‐till treatments had soybean yields that were greater than the traditional plow system. The 5‐yr mean soybean yield from the no‐till treatment was about 6% greater than the commonly used double‐disk system and 11% greater than the traditional plow system. The 5‐yr mean grain sorghum yield from the no‐till treatment was about 6% greater than the commonly used double‐disk system and 9% greater than the traditional plow system. For soybean, the yields from the no‐till and no‐till with cultivation treatments were not different. However, since 1986, the grain sorghum yield from the no‐till treatment has averaged 6 bu/acre higher (about 4%) than the no‐till with cultivation treatment. This difference was also observed in 1983 and was attributed to moisture stress associated with cultivation. Soil organic matter tended to be greatest for the continuous no‐till system and lowest for the plow system. The plow system had slightly less penetration resistance within the 4‐ to 8‐in. depth, whereas, the double‐disk system was slightly greater within the 2‐ to 4‐in. depth. Draft and power requirements for planting in the selected tillage and planting systems were not different. The major difference among the tillage and planting systems was residue cover remaining after planting (Table ). No‐till had the most residue cover, but there was no appreciable accumulation of residue over the 10 yr of continuous use of the tillage and planting systems. Operations for the tillage and planting systems evaluated. Tillage and planting system Operations No‐till No‐till w/ cultivation Disk Double‐ Disk Chisel Plow Shred stalks (fall) X X Fall moldboard plow X Fall chisel plow X Knife apply NH 3 X X X X X X Apply herbicide X X X X X X Disk X X Disk X X X X Plant X X X X X X Apply herbicide X X X X X X Crop cultivate X X X X X Grain yield for the last 5 yr of measurement. Percentage of annual mean yield, % Tillage and <jats