Tillage System Effects on Soil and Plant Nutrient Distributions on Vertisols

Heavy clay soils, such as vertisols of the Texas Blackland Prairie (Houston Black clay [fine, montmorillonitic, thermic Udic Pellusterts]), are difficult to manage for crop production. Such soils typically require high draft for tillage; have limited opportunities for mobility, tillage, and planting; and produce variable crop performance when associated with highly variable weather patterns. This study compared the soil and plant nutrient distributions and yield performance of an experimental no‐till farming system with a farming system using modified conventional chisel‐till soil management. Raised wide beds and controlled traffic were used for both systems. Wheat ( Triticum aestivum L.), corn ( Zea mays L.), and grain sorghum [ Sorghum bicolor (L.) Moench] no‐till yields were similar to those on chisel‐tilled plots. Plant nutrients became stratified near the soil surface, with greater concentrations of C, N, and P occurring in the near‐surface layers after a single 3‐yr crop rotation cycle with no‐till than with the chisel‐till system. Grain yield responses to fertilizer rates were not affected by nutrient distribution. Nitrogen and P concentrations in plants tended to be high in the no‐till system. Economic return for applied N was the same across tillage practices for each crop. The data demonstrated that the vertisol clay soils of the Texas Blackland can be farmed with no‐till without comprising crop yield potential. Research Question Vertisols and high clay soils with vertic properties are poorly drained when wet, form open cracks when dry, require timely tillage, till‐up as large clods and require high energy for tillage. If no‐till can be used on these soils, then many of the tillage problems could be avoided. This study compared nutrient distributions in the soil and plants and crop production between conventional chisel‐till and no‐till systems on vertisols. Literature Summary Chisel‐till and no‐till systems have been described for use on vertisols in the Blackland Prairie section of Texas. Annual crop rotations of corn, wheat, grain sorghum, and cotton were conducted with the main difference between the two tillage systems being annual mixing of residues and nutrients into the profile with chisel‐till and no mixing with the no‐till system. Crop yields were similar between the two tillage systems when plant stands and tillering were equal. Procedures were developed for using raised wide beds and controlled traffic. Bed forming, planting, and fertilizer application machines and procedures were developed for vertisols. Other investigators have found equal yields for several tillage systems on vertisols. No‐till systems produce stratification of nutrients, although detailed stratification has not been studied for vertisols. Foliar concentrations of nutrients are as high from surface fertilizer applications and no‐till, as they are with deep applications and conventional tillage. Study Description This paper compares crop performance over 6‐yr with no‐till and with chisel‐till for annual rotations of winter wheat, grain sorghum, and corn. Tillage treatments were subdivided between preplant knifing and postemergence surface banded sidedressing of N‐P fertilizer at four rates, including zero rate. Weed control was by herbicides with identical treatments for no‐till and chisel‐till. Soil compaction was minimized by use of raised wide beds and traffic‐lane furrows. Nutrient distributions in the surface soil layers and plant leaf and grain contents of N and P were compared for tillage systems. Applied Questions 1. Can yields be maintained on poorly drained vertisols without tillage? Yields were not different between annual chisel‐till and 6 yr of no‐till for rotations of winter wheat, grain sorghum, and corn over two cycles of the three‐crop rotation. 2. What was the effect of weather? Rainfall patterns were highly variable over the 6‐yr study, which caused large year‐to‐year differences in yields, but not between tillage systems for any 1 yr. 3. Did tillage system affect plant concentrations of nutrients? Crops under no‐till had increased foliar concentrations of N and P over chisel‐till crops, but there were no differences in nutrient concentrations between knifed and sidedressed fertilizer applications, or in concentrations in the grain. 4. Did applied nutrients become stratified? The nutrients C, N, and P were stratified in the top 4 in. of no‐till top‐soil with high concentrations in the top 0‐ to 1‐in. and 1‐ to 2‐in. layers after 3 yr. The stratification continued through 6 yr, but there was no indication that this impaired nutrient availability to the crops. Because tillage of vertisols (and other vertic soils) is difficult and costly, no‐till should be considered as a management alternative. Study conditions. Soil: Houston Black clay (fine, montmorillonitic, thermic Udic Pellusterts) Tillage system: 1. Chisel‐till 1. No‐till Fertilizer application: 1. Preplant knifed 4‐in. deep 2. Postplant sidedressed surface‐banded fertilizer rates, N/P 1. 0/0, 20/3.5, 45/7.9, 95/16.7 (wheat) 2. 0/0, 20/3.5, 95½16.7, 145/25.5 (corn) 3. 0/0, 20/3.5, 70/12.3, 120/21.1 (sorghum) Starter fertilizer, N/P: 5/7.5 (all crops) except 010 treatment Varieties: 1. Wheat (cv. Mit) 2. Corn (cv. DeKalb XL72AA) 3. Sorghum (cv. Paymaster 1125 DR) Herbicide: 1. Roundup 2. Banvel 3. MCPA 4. Atrazine 5. Dual 6. Bladex Growing seasons: 1. Air temperature similar to 80‐yr average 2. Precipitation varied widely year‐to‐year and from 80‐yr average