Tillage Intensity Effects on Corn and Grain Sorghum Growth and Productivity on a Vertisol

Sustainable production systems and conservation tillage practices are needed to control water erosion on vertisols. Five levels of tillage intensity were tested for 3 yr for effects on growth and yield of corn (Zea mays L.) and grain sorghum [Sorghum bicolor (L.) Moench.] on a Houston Black clay soil (fine montmorillonitic, thermic Udic Pellusterts). Tillage intensity treatments included: chisel plow with secondary tillage; disk only; no-till with residue rakes at planting; no-till with midseason cultivation; and no-till. Corn plant populations were greater in tilled treatments than in no-till treatments in 2 of the 3 yr. Corn above-ground biomass production was generally reduced in no-till treatments early in the growing season, but by silking differences among treatments were not significantly different. Corn yielded 840 lb/acre more on average with tillage than with no-till. Plant population differences accounted for much of the difference in corn grain yields, with low plant populations restricting yield in some years. Grain sorghum populations were not consistently affected by tillage intensity, and biomass production was Jess sensitive to tillage intensity than corn. Grain sorghum yields were as large or larger in no-till treatments than in tilled treatments, except in one instance where population was reduced. Research QuestionConservation tillage has been slow to be adopted in the Blackland vertisols of central Texas. Concerns remain on soil compaction, crop establishment, timeliness of operations, and water management, as well as the cost of equipment needed for new practices. This study examines a range of tillage practices and the resulting effect on the stand, early growth, and yield of corn and grain sorghum in heavy clay soils. Literature SummaryRecently, a management system was developed for the Central Texas Blacklands which uses 5 ft wide beds with 20 in. wide furrows between beds. This system restricts traffic to the furrows and provides surface drainage for the beds. Beds may be tilled out and reconstructed every year or the beds may be maintained by no-till management practices. We have compared no-till practices with chisel tillage for several years. After 10 yr of no-till practices, the soil developed strong surface layers, which could restrict plant rooting. Study DescriptionFive management systems were tested in this 3-yr study: (i) complete residue burial with chisel plow, disking and field cultivation prior to rebedding; (ii) disk only with rebeddbig and three forms of no-preplant tillage; (iii) a slot-plant; (iv) slot-planting with residue rakes to clean the row; and (v) slot-planting with a midseason cultivation. Corn and grain sorghum were planted as early as soil temperature and soil water content would allow. Fertilizer was applied to the corn plots at a rate of 145 lb N/acre and 135 lb P₂O₅/acre. Grain sorghum was fertilized at a rate of 120 lb N/acre and 110 lb P₂O₅/acre prior to planting. Starter fertilizer was applied to both the corn and grain sorghum at a rate of 5 lb N/acre and 39 lb P₂O₅/acre. Crop emergence rates and final populations were measured. Early season above-ground-biomass and grain yields were also measured. Applied QuestionsDid management practices affect emergence rates and plant stands? Corn emergence was usually more uniform with greater amounts of tillage. Corn populations were often reduced in any of the three no-till systems. Grain sorghum emergence was also more uniform in the tilled plots than the no-till plots, but populations were usually similar among all treatments. Were plant growth rates and yields affected by the different management practices? Early season corn growth in the no-til1 plots often lagged behind that in the tilled plots. By silking, differences among management systems were not measurable. Grain sorghum growth also was delayed in the early season, but at flowering there was little difference among management systems. Corn yields were reduced in the no-till systems in 2 of the 3 yr of the study (Table 1). However, there was little difference in corn yield between the complete tillage and disk tillage management systems. Grain sorghum yields were similar in all of the management systems tested. What made the most difference in yield potential among the management systems? Plant populations appeared to have the most effect on corn yields. Corn populations were generally too small for the best potential yield. Plant population had a significant positive correlation with corn grain yields in 1993 and 1994, in which there were differences in populations among tillage treatments. In 1993: Yield (lb/acre) = 4560 + 130 × plants (thousands/acre): r² = 0.45 In 1994: Yield (lb/acre) = 1000 + 200 × plants (thousands/acre): r² = 0.47 Plant population alone could account for nearly half of the variation in corn grain yields among plots. Grain sorghum appeared well adapted to the conditions created by no-till management in this study. Table 1Corn grain yields for years 1992 to 1994 with five levels of tillage intensity. Tillage 1992 1993 1994 ---------lb/acre-------Complete-till603076206860Reduced-till641077205240No-till/raked623068004760No-till/cult513066705480 No-till585065704800 LSD(0.05)5753481180