Soil Health Assessment in Double Cropping Wheat Systems Across Texas

Conservation practices such as no-tillage and double-cropping are less common in the Southern Great Plains, especially Texas, compared to other regions of the United States. These practices have the greatest potential to reduce wind erosion and improve soil health in the typical sandy soils found in this region. However, research is needed to identify double cropping systems suited to the area and determine their effect on soil health. The overall objective of these series of experiments was to evaluate the effects of conservation management practices on various agroecosystems across Texas (Beeville, Lubbock, and Thrall) by measuring soil properties that are indicative of soil health. Specifically, we wanted to determine the effects of double cropping systems, under multiple tillage regimes, on select soil biological indicators across Texas. Secondly, we wanted to evaluate a novel assay in the simultaneous determination of enzymes compared to the sums of individually assayed enzymes, while also evaluating its use as a biogeochemical nutrient cycling index. Implementation of a secondary crop in a continuous wheat production system combined with reduced or no tillage, generally increased soil health indicators when compared to conventionally tilled fallow systems. Nutrient cycling potential of carbon, nitrogen, phosphorus, and sulfur was generally greater at 0-5 and 5-15 cm in cropping systems that implemented a secondary crop. Reduced tillage practices (no-till and strip-till) generally had greater activity at 0-5 cm with greater activity in conventionally tilled plots at 5-15 cm. Potassium permanganate oxidizable carbon was generally greater in plots that incorporated a cover crop mix at 0-5 cm with greater levels determined in conventionally tilled plots at 5-15 cm. Soil organic carbon measurements were not as sensitive to cropping systems and tillage treatments at 0-5 and 5-15 cm across all locations, with limited significance determined between treatments. The simultaneous determination of β-glucosidase, β-glucosaminidase, acid phosphatase, and arylsulfatase exhibited a significant positive linear relationship with the sum of individual enzyme activities measured in Beeville (R2 = 0.65), Lubbock (R2 = 0.85), and Thrall (R2 = 0.96). Overall, simultaneous determination of enzyme activity was greatest in systems that implemented a secondary crop at 0-5 and 5-15 cm when compared back to the fallow system. Conservation tillage management practices (no-till and strip-till) measured greater enzyme activity when compared to conventional tillage at 0-5 cm, but the opposite was measured at 5-15 cm with greater enzyme activity measured in conventionally tilled systems. This is likely attributed to residue retention at soil surface with conservation tillage practices and inversion of organic residues deeper into soil profile with conventional tillage. This study suggests that implementation of a secondary crop, through double cropping, and reduced tillage, such as strip-till and no-till, have the potential to be used as a viable management strategy across Texas in terms of increasing the soil health of a system. Limitations of the length of the study was unable to determine significant differences or trends in soil organic carbon and the need to conduct long-term double cropping studies is still needed to evaluate the complex dynamics associated with management and soil organic matter.