A Soil Quality Framework for Evaluating the Impact of CRP

As the demand for food, feed, fiber, and, most recently, bio-energy increases, more land may be converted from native conditions for arable uses. Our objective was to evaluate soil quality under native forest, arable land being used for continuous barley (Hordeum valgare L.) production and land that had been tilled and subsequently enrolled in the Conservation Reserve Program (CRP) for at least 18 years. Several physical, chemical, and biological soil quality indicators were measured and a soil deterioration index (DI) was calculated using forest soil as the reference. Results indicated that most organic matter under forest resided on soil surface and was not mixed with mineral soil due to lack of activities by large soil fauna (e.g., earthworms). Soil samples from disturbed areas had a higher organic matter content, which caused most soil quality indicators to be considered ‘improved’ and resulted in better DIs for agricultural and CRP land than for forest soils. This study emphasized the importance of choosing an appropriate reference point for soil quality assessments, especially when data representing one or more key soil processes are missing.

The soil erodibility index (EI) of Conservation Reserve Program (CRP) lands, which was the major criterion for CRP enrollment, was assessed for six counties in southwestern Kansas using USGS seamless digital elevation model data and Geographical Informational System techniques. The proportion of land areas with EI values of 8 or lower was less than 1% of the entire study area and most of the land areas (72.5%) were concentrated on EI values between 8 and 24. Although land acreage with EI values of 24 or higher decreased dramatically, the proportion of CRP lands to the other land-use types did not change much from low to high EI levels. The soil EI and physical soil characteristics of the CRP lands were compared to those of other land-use types. In general, the mean EI values of the land-use types were strongly correlated with physical soil properties, including organic matter content, clay content, available water capacity, permeability, and texture. CRP lands were compared in detail with cropland in terms of their soil characteristics to infer the pivotal cause of the land transformation. Although there was no significant statistical difference in EI between cropland and CRP soils, soil texture, soil family, and permeability were statistically different between the two. Statistical analyses of these three variables showed that CRP soils had coarser texture and higher permeability on average than cropland soils, indicating that CRP lands in the study area are drier than cropland soils. Therefore, soil moisture characteristics, not necessarily soil erosion potential, might have been the key factor for CRP enrollment in the study area.

ABSTRACTTo precisely comprehend the impacts and determine the most suitable nutrient management and organic farming practices for sustainable agro‐ecosystems, assessment of soil quality at surface and sub‐surface depth is crucial. This study aims to assess the soil quality in response to different farming practices under maize‐wheat sequences. At two soil depths (0–0.15 m; and 0.15–0.30 m), physical, chemical and biological indicators of soil quality were evaluated under eleven nutrient management practices, including 100% NPK (RDF); 100% NPK + FYM at 10 t ha−1 (RDFM); 100% NPK + lime (RDFL); Organic farming practices (OF)s; natural farming system practiced using products of Desi cow (NFS‐DC); natural farming system practiced using products of Crossbred cow (NFS‐CC); natural farming system practiced using products of Buffalo (NFS‐BF); OF+25%NPK; NFS‐DC + 25%NPK; NFS‐CC + 25%NPK; and NFS‐BF + 25%NPK, which were arranged in a completely randomised‐block design. For the soil quality assessment, minimum data set (MDS) of quality indicators was chosen using principal component analysis, and soil quality index (SQI) was then determined using a weighted additive technique. Results revealed that maize and wheat grain equivalent yield, available nutrients (N, P and K) were recorded higher under RDFM, followed by RDFL. However, water holding capacity, bulk density, aggregate stability, saturated hydraulic conductivity, available S, organic carbon, microbial count, microbial biomass C and N, and enzymatic activities greatly improved under OF+ 25%NPK. Among NFS practices, NFS‐DC outperformed NFS‐CC and NFS‐BF in all the studied parameters. Available N, S, K, organic carbon, microbial biomass C, mean weight diameter and bulk density were selected as MDS. At 0–0.15 m soil depth, soil quality index (SQI) was recorded highest under organic farming+25%NPK (0.99), followed by RDFM (0.98), while the lowest value of SQI was observed under RDF (0.88). NFS‐DC witnessed 1.27% and 1.97% higher values of SQI over NFS‐CC and NFS‐BF, respectively. The SQI value decreased in the sub‐surface soil layer (0.15–0.30 m), however treatment‐wise trend remains the same. At surface soil (0–0.15 m soil depth), available N contributed the most (35.7%) to SQI, followed by OC (27.9%), MBC (26.9%), available K (2.34%), S (0.91%) and MWD (0.51%). This study advocates the addition of organic manures with small quantity of chemical fertilisers that is, organic farming practices +25%NPK for maintaining the soil health and quality which could sustain/enhance system' productivity in a long run.

Chemical and microbial aspects of soil quality are an important consideration when evaluating the benefits of soil conservation efforts such as the Conservation Reserve Program (CRP). The objective of this study was to evaluate the quality of CRP and wheat‐fallow (W‐F) soils using soil biological and chemical parameters and C and N mineralization processes. The study was conducted on 20 CRP/W‐F paired sites in eastern Washington, on Ritzville silt loam (coarse‐silty, mixed, mesic Calciorthidic Haploxerolls). Soils collected from the paired fields were analyzed for chemical and biological parameters that have been suggested as indicators of soil quality. Potential enzyme activities and soil N were higher in the CRP soil than the W‐F soil. Although there were no significant differences in total organic carbon (TOC) or microbial biomass carbon (MBC) the C mineralization potentials and C pools were significantly different between the CRP and W‐F soils. Soil biota measurements showed there was greater active bacterial biomass in the CRP soil but greater fungal‐feeding nematodes, flagellates, and amoebae in the W‐F soil. The C mineralization study suggests that there is a significant increase in the secondary C pool of the CRP soil, which may indicate a buildup of higher quality soil organic matter and the potential for higher enzyme levels. When grass or straw was added to each soil type, the W‐F soil produced more CO2 with either substrate than the CRP soil, indicating C limiting conditions in the W‐F soil. Since it is unknown what constitutes good soil quality, these shifts in chemical and biological parameters may seem subtle. However, in general, trends in the data indicated that soil quality in the CRP was improved after 4 to 7 yr, compared with its previous management in W‐F cropland.

Water and energy demands associated with bioenergy crop production on marginal lands are inextricably linked with land quality and land use history. To illustrate the effect of land marginality on bioenergy crop yield and associated water and energy footprints, we analyzed seven large-scale sites (9–21 ha) converted from either Conservation Reserve Program (CRP) or conventional agricultural land use to no-till soybean for biofuel production. Unmanaged CRP grassland at the same location was used as a reference site. Sites were rated using a land marginality index (LMI) based on land capability classes, slope, soil erodibility, soil hydraulic conductivity, and soil tolerance factors extracted from a soil survey (SSURGO) database. Principal components analysis was used to develop a soil quality index (SQI) for the study sites based on 12 soil physical and chemical properties. The water and energy footprints on these sites were estimated using eddy-covariance flux techniques. Aboveground net primary productivity was inversely related to LMI and positively related to SQI. Water and energy footprints increased with LMI and decreased with SQI. The water footprints for grain, biomass and energy production were higher on lands converted from agricultural land use compared with those converted from the CRP land. The sites which were previously in the CRP had higher SQI than those under agricultural land use, showing that land management affects water footprints through soil quality effects. The analysis of biophysical characteristics of the sites in relation to water and energy use suggests that crops and management systems similar to CRP grasslands may provide a potential strategy to grow biofuels that would minimize environmental degradation while improving the productivity of marginal lands.

Sustainability of our use of the environment, including sustainability of both the resource base and the economic system, has been of increasing interest in rural land use analysis. The U.S. Conservation Reserve Program (CRP) is part of a series of land and soil conservation measures dating back to the Dust Bowl era of the 1930's that have significant implications for preserving quality grassland resources. In order to assess the natural resource capability of CRP lands and make appropriate long term recommendations relative to rural land use management, this study incorporated remote sensing and GIS approaches to evaluate interrelationships among spatially co‐varying physical resource variables. Results indicate an inverse relationship between CRP lands and aquifer thickness, and a direct relationship between soil quality and physiography with CRP lands. In addition, findings support the use of CRP lands for grasslands in southwest Kansas as more conducive to longer term regional sustainability.

ABSTRACTA study was conducted to evaluate selected soil quality indicators in lands that have been in Conservation Reserve Program (CRP), which is a federal program in the United States offering annual rental payments and cost-share assistance to farmers who establish long-term vegetation covers on their erosion prone lands. The study site has semi-arid climate, and soils with grass vegetation covers for 15 years were compared with adjacent cultivated croplands that have never been in the CRP. Field measurements were performed and surface soil samples (0–0.15 m) were collected from multiple sites having either coarse textured or fine textured soils. Soil measurements assessed included bulk density (BD), penetration resistance (PR), wet aggregate stability (WAS), dry aggregate size distribution (DASD), soil organic matter (SOM), permanganate oxidizable carbon, nitrate nitrogen, extractable potassium and phosphorus, electrical conductivity, pH, sodium adsorption ratio, and soil micronutrients (copper, iron, manganese, and zinc). Results showed a significant effect of CRP management compared to the cropped fields for BD, WAS, and PR only, with the CRP fields being less compacted and having higher WAS than the cropped lands. CRP land did not significantly differ from cropped lands in SOM and for many other measurements. The effect of soil texture was significant for DASD, SOM, copper, and manganese, with the fine textured soils having more favorable measurements than the coarse textured soils. CRP management did not produce significant increase in topsoil SOM compared to cropped lands of the study area.

Conservation Reserve Program (CRP) lands provide ecosystem service benefits that exceed land rental payment costs

Microbial properties of Kenoma silt loam soil in Coffey County, Kansas, were investigated for a native tallgrass prairie, a field currently under cultivation, and a previously cultivated field that was reseeded to native grasses in 1986 as part of the Conservation Reserve Program (CRP). Soil samples were taken from the surface 10 cm and analyzed for soil respiration, microbial biomass carbon (C) and nitrogen (N), N availability, and dehydrogenase activity. In comparison to soils in native prairie, measures of microbial quality in soils under cultivation decreased as follows: microbial biomass C and N by 67%, nitrogen availability by 37%, dehydrogenase activity by 68%, and respiratory rate by 69%. When CRP land was compared with soils in cultivation, no significant differences could be detected in terms of microbial biomass N, N availability, and dehydrogenase activity. The CRP land showed lower values of microbial biomass C, but a significantly higher respiratory rate. These results led to three important conclusions: First, the results strongly confirm that cultivation has a profound impact on native prairie soils. Second, the levels of soil microbial quality parameters in the reseeded prairie were not similar to those in the native prairie after a period of 6 years. Third, a higher respiratory rate in the reseeded prairie indicates a response of the soil microbial community to the reestablishment of permanent prairie vegetation. The latter point also was supported by a greater proportion of active pools of C and N in the reseeded prairie.

A minimum data set and soil quality index to quantify the effect of land use conversion on soil quality and degradation in native rangelands of upland arid and semiarid regions

Abstract. Soil quality (SQ) assessment has long been a challenging issue, since soils present high variability in properties and functions. This paper aims to increase the understanding of SQ through the review of SQ assessments in different scenarios providing evidence about the interrelationship between SQ, land use and human health. There is a general consensus that there is a need to develop methods to assess and monitor SQ for assuring sustainable land use with no prejudicial effects on human health. This review points out the importance of adopting indicators of different nature (physical, chemical and biological) to achieve a holistic image of SQ. Most authors use single indicators to assess SQ and its relationship with land uses – soil organic carbon and pH being the most used indicators. The use of nitrogen and nutrient content has resulted sensitive for agricultural and forest systems, together with physical properties such as texture, bulk density, available water and aggregate stability. These physical indicators have also been widely used to assess SQ after land use changes. The use of biological indicators is less generalized, with microbial biomass and enzyme activities being the most selected indicators. Although most authors assess SQ using independent indicators, it is preferable to combine some of them into models to create a soil quality index (SQI), since it provides integrated information about soil processes and functioning. The majority of revised articles used the same methodology to establish an SQI, based on scoring and weighting of different soil indicators, selected by means of multivariate analyses. The use of multiple linear regressions has been successfully used for forest land use. Urban soil quality has been poorly assessed, with a lack of adoption of SQIs. In addition, SQ assessments where human health indicators or exposure pathways are incorporated are practically inexistent. Thus, further efforts should be carried out to establish new methodologies to assess soil quality not only in terms of sustainability, productivity and ecosystem quality but also human health. Additionally, new challenges arise with the use and integration of stable isotopic, genomic, proteomic and spectroscopic data into SQIs.

The Conservation Reserve Program (CRP) was designed to reduce soil erosion and curb agricultural overproduction by converting highly erodible agricultural land to various forms of perennial habitat. It has had an incidental benefit of providing habitat for wildlife and has been beneficial in reversing population declines of several grassland bird species. However, the mechanisms behind these reversals remain unknown. One such mechanism may be differences in food availability on CRP vs. non-CRP land or between different types of CRP. The influence of CRP habitat type on the abundance of arthropod prey used by grassland birds has not been previously explored. We compared the abundance and diversity of arthropods among four CRP habitat types in Texas [replicated plots of exotic lovegrass (Eragrostis curvula), Old World bluestem (Bothriochloa ischaemum), mixed native grasses with buffalograss (Buchloë dactyloides) and mixed native grasses without buffalograss] and native shortgrass prairie. Attention was focused on adult and juvenile spiders (Order Araneae), beetles (Coleoptera), orthopterans (Orthroptera: grasshoppers and crickets) and lepidopterans (Lepidoptera: butterflies and moths), as these taxa are the primary prey items of grassland birds during the breeding season. Arthropod diversity and abundance were higher on indigenous prairie compared to CRP, reflecting differences in vegetative diversity and structure, but there were no differences in arthropod richness or abundance among CRP types. These results indicate that, although CRP is not equivalent to native prairie in terms of vegetation or arthropod diversity, CRP lands do support arthropod prey for grassland birds. More direct assays of the survivorship and fitness of birds on CRP compared to native shortgrass prairie are clearly warranted.

We examined the effects of habitat fragmentation and vegetation structure of shortgrass prairie and Conservation Reserve Program (CRP) lands on predation rates of artificial and natural nests in northeastern Colorado. The CRP provides federal payments to landowners to take highly erodible cropland out of agricultural production. In our study area, CRP lands have been reseeded primarily with non-native grasses, and this vegetation is taller than native shortgrass prairie. We measured three indices of habitat fragmentation (patch size, degree of matrix fragmentation, and distance from edge), none of which influenced mortality rates of artificial or natural nests. Vegetation structure did influence predation rates of artificial nests; daily mortality decreased significantly with increasing vegetation height. Vegetation structure did not influence predation rates of natural nests. CRP lands and shortgrass sites did not differ with respect to mortality rates of artificial nests. Our study area is only...

Microbial biomass and N cycling under native prairie, conservation reserve and no-tillage in Palouse soils

The Conservation Reserve Program (CRP) has been a major factor in land transitions out of intensive row‐crop management on marginally productive lands in the central United States. While CRP can protect these more environmentally sensitive lands against erosion and potential nutrient loss, information on how CRP affects soil quality over time is limited. Using a chronosequence with 0–40 yr of CRP conversion history, we evaluated soil quality under different land use intensities (CRP, pasture, row crop) using the Soil Management Assessment Framework (SMAF). Effects of slope classes (higher [14–25%] and lower [2–14%]) and soil depth (0–120 cm) were also evaluated. Our results show that the soils were functioning at 84 and 78% of their theoretical capacity under CRP and row crop, respectively. Conversion to CRP enhanced overall soil quality by increasing soil biological, physical, and chemical attributes, but soil nutrient availability decreased due to the absence of fertilizer application. Increasing soil organic C (SOC) enhanced overall soil quality because of its impact on soil biological, physical, chemical, and nutrient conditions. Conversion to CRP will likely have greater benefits for more environmentally sensitive soils (i.e., higher slope) as demonstrated by structural equation modeling. Land use effects were also depth dependent, with more prominent effects within the 0‐to‐5‐cm than the 5‐to‐15‐cm depth increment. Overall, our methods focused on key soil quality indicators, confirmed ecological benefits of CRP conversion, and provided guidance for improved and simplified land management recommendations.