Browsing by Author "Gyawali, Ayush Joshi"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Quantifying short-term responsiveness and consistency of soil health parameters in row crop systems. Part 1: Developing a multivariate approach
    Gyawali, Ayush Joshi; Strickland, Michael S.; Thomason, Wade E.; Reiter, Mark S.; Stewart, Ryan D. (Elsevier, 2022-05-01)
    Quantifying soil health requires measuring different physical, chemical and biological soil properties, yet limits in time and resources often restrict the number of parameters that can be analyzed. The main objective of this research was to identify soil health parameters that showed measurable and consistent responses to reduced tillage and cover cropping over a short (2-year) study period. In September 2015, four treatments – reduced tillage with cover crops, reduced tillage without cover crops, conventional tillage with cover crops and conventional tillage without cover crops – were installed in five sites across Virginia. Sites were managed for corn or tobacco production. Soils were analyzed for 32 properties associated with soil health, and cash crop yields were also measured in September 2016 and September 2017. A multivariate approach was used to detect treatment differences and determine parameters driving those differences. We then developed two new indices to quantify the responsiveness and consistency of soil health parameters. The results showed that surface soil layers had more parameters with significant differences between treatments than subsurface layers. Tillage effects were observed within 0.5 years, which may be due to the lack of tillage history in 4 of the 5 sites. Cover crop effects appeared after 1.5 years, indicating that this practice can also induce changes in soil properties over relatively short periods. Soil aggregate stability, potassium, calcium, magnesium, boron and cash crop yield were the most responsive parameters to reduced tillage and cover crop practices, while aggregate stability also showed high consistency. These findings suggest that aggregate stability effectively indicated short-term changes in soil health within row cropping systems of Virginia.
  • Thumbnail Image
    Talking SMAAC: A New Tool to Measure Soil Respiration and Microbial Activity
    Gyawali, Ayush Joshi; Lester, Brandon J.; Stewart, Ryan D. (Frontiers, 2019-05-29)
    Soil respiration measurements are widely used to quantify carbon fluxes and ascertain soil biological properties related to soil microbial ecology and soil health, yet current methods to measure soil respiration either require expensive equipment or use discrete spot measurements that may have limited accuracy, and neglect underlying response dynamics. To overcome these drawbacks, we developed an inexpensive setup for measuring CO2 called the soil microbial activity assessment contraption (SMAAC). We then compared the SMAAC with a commercial infrared gas analyzer (IRGA) unit by analyzing a soil that had been subjected to two different management practices: grass buffer vs. row crop cultivation with tillage. These comparisons were done using three configurations that detected (1) in situ soil respiration, (2) CO2 burst tests, and (3) substrate induced respiration (SIR), a measure of active microbial biomass. The SMAAC provided consistent readings with the commercial IRGA unit for all three configurations tested, showing that the SMAAC can perform well as an inexpensive yet accurate tool for measuring soil respiration and microbial activity.
  • Thumbnail Image
    What We Talk about When We Talk about Soil Health
    Stewart, Ryan D.; Jian, Jinshi; Gyawali, Ayush Joshi; Thomason, Wade E.; Badgley, Brian D.; Reiter, Mark S.; Strickland, Michael S. (American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, 2018-11-01)
    Despite a nationwide emphasis on improving soil health in the United States, current measurement protocols have little consistency. To survey assessment practices, we conducted a meta-analysis of cover crop (n = 86) and no-tillage (n = 106) studies and compiled reported indicators, cropping systems, and soil sampling protocols from each. We then analyzed which indicators significantly responded to cover crop usage after 1 yr and 2 to 3 yr. Our results showed that out of 42 indicators, only 8 were reported in >20% of studies. Thirteen indicators showed >10% relative response after 1 to 3 yr; the remainder lacked either sufficient observations or consistent results. Looking forward, we propose that emphasis should be placed on (i) pursuing dynamic indicators (e.g., aggregate stability), (ii) standardizing sampling protocols, and (iii) developing a common framework for information sharing. These efforts will generate new insight into soil health across systems, ultimately ensuring that soil health science is useful to producers and regulators.