Soil Quality Assessmnet Using Long-Term Conservation Reserve Program.

Although, soil quality (SQ) can be defined in a number of ways however it is adhered to agricultural and environmental usage. SQ as defined by the Natural Resource Conservation Service (NRCS) is the capacity of a specific kind of soil to function, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitation. Using fifteen-year old established (1999-2014) stand of Conservation Reserve Program (CRP) land; first ten-year unharvested and five-year harvested was undertaken to assess soil quality indices (SQI). Treatments imposed after completion of first ten-year as unharvested were five levels of nitrogen (i.e. 0, 10, 20, 40, and 80 kg N/ha) and three types of management strategies; Management-A: harvest of biomass in March or April after winter senescence of plants (winter, dry biomass), Management-B: 1^st harvest in May (spring, green biomass) and 2^nd harvest in March or April (winter, dry biomass), and Management-C: Multiple harvests during May through October (spring through autumn, green biomass) in a randomized complete block design (RCBD) set up. These N-rates and Management strategies were arranged in a strip-block restriction on randomization with four replications. Meter deep (0-100 cm) detail soil sampling performed first in 2009, and second in 2014 were sectioned into three depths (0-20, 20-50, 50-100, and cumulative depths 0-100 cm). Following inductive approach, SQI was assessed based on five important but basic soil chemical, biological and physical properties, namely Active Carbon (mg/kg), Particulate Organic Matter-Pool (Mg/ha), Microbial Biomass Carbon (mg/kg), Basal Respiration (mg CO₂-C/kg/day), and Urease Enzyme Activity (NH₄-N mg/kg/hr). SQI was computed based on 0 to 1 scale from lowest to highest. Overall, N-rates did not play any roles in SQI. SQI was found significantly higher in 2014 than 2009 soil (p ≤ 0.05). The three Managements exhibited significantly higher SQI in 2014 compared to base year 2009 (p ≤ 0.05), however, Management-A superseded –B and –C. Depending on percent expressed in SQI variability, among five variables, AC ranked 1^st followed by BR, MBC, U-Activity, and POM-Pool. Results showed that harvesting aboveground biomass in CRP land as bioenergy feedstock has significantly improved soil quality and proved to be win-win situation, both for federal government agencies and producers/ranchers.