15 pages, Cover crops—crops grown primarily to protect and improve soil—are widely considered to be an important component of sustainable agricultural systems because their use can provide multiple ecosystem services without compromising yields over time. Specialty crops—fruits, vegetables, and horticultural crops—are increasingly important to US agriculture and food security and uniquely vulnerable to climate-related problems that cover crops can help to address. Yet far less research has been conducted on cover crop use by farmers who grow mainly specialty crops, compared to the much larger body of research on farmers who principally grow row crops like corn (Zea mays) and soybeans (Glycine max). In this study, we draw on survey data from a stratified, random sample of 881 specialty crop growers in Michigan and Ohio to accomplish two main goals. First, we seek to characterize cover crop use among this important group of farmers, focusing on types of cover crop used and use of multiple types. Second, we examine the relationship between cover crop use on vegetable and fruit farms and key social and economic factors, with particular attention to farmers’ environmental values, adherence to organic principles, and sources of information. According to survey results, cover cropping is more likely when farmers (1) manage certified organic (p < 0.01) or organic-in-practice (p < 0.05) farms; (2) report being influenced by private crop consultants (p < 0.01); (3) attach high importance to agri-environmental goals (p < 0.01); and (4) grow vegetable crops instead of or in addition to fruit crops (p < 0.001). No relationship was found to exist between cover cropping and farmers’ concerns about climate-related risks, education level, or perceived self-efficacy. We conclude by suggesting that the importance of structural factors to farmers’ decisions about cover crops should not be underestimated. Promoting and strengthening the market for organic food may be the most direct pathway toward increasing the number of farmers who use cover crops. Historically important entities in agricultural networks, including cooperative extension and conservation nongovernmental organizations, might enhance their impact on cover crop use by forming new partnerships with private crop consultants.
12 pages, via Online journal, Corn (Zea mays) grown in the southern Piedmont requires 200 to 280 kg nitrogen (N) ha−1 annually and requires up to 0.87 cm of water per day, making groundwater systems susceptible to nitrate (NO3−) leaching. A perennial white clover (Trifolium repens L.) living mulch (LM) system may reduce NO3-N leaching by using legume N to replace mineral N, though little information is available on such a system in the southern Piedmont. Therefore, a HYDRUS-1D model was used to simulate water and NO3-N flux in three cover crop systems. Cereal rye (Secale cereal L.) (CR), crimson clover (Trifolium incarnatum L.) (CC), and a white clover LM were fertilized with 280, 168, and 56 kg N ha−1. The HYDRUS-1D model was calibrated and validated with observed water contents and NO3-N data that were collected over two years. Water and NO3-N flux models were created for each treatment and evaluated using coefficient of determination, percentage bias, and index of agreement, and showed good agreement to observed data. Nitrate leaching below 1 m in 2015/2016 was 23.5, 12.7, and 21.4 kg ha−1 for the CC, LM, and CR treatments, respectively, but was less than 1 kg ha−1 for all treatments in 2016/2017 due to prolonged drought. Differences in leached NO3-N among treatments were attributed to variation in mineral N application rate and NO3-N uptake by cover crops. Overall, results suggest that the use of a perennial LM system may reduce NO3-N leaching when compared to annual CC and CR cover crop systems.
11 pages, via Online journal, The Soil Vulnerability Index (SVI) was developed by the USDA Natural Resources Conservation Service (NRCS) to identify inherent vulnerability of cropland to runoff and leaching. It is a simple index that relies on the SSURGO database and can be used with basic knowledge of ArcGIS. The goal of this study was to investigate a relationship between constituent (sediment and nutrient) loadings and fraction of the watershed in each SVI class. The SVI maps were developed for each of the seven subwatersheds of the Mark Twain Lake watershed in Missouri, which were similar in soil conditions and climatic variability. The SVI assessment was performed by investigating if the distribution of the SVI for cropland in each subwatershed could help explain measured 2006 to 2010 sediment and nutrient loads better than crop distribution alone. Regression analyses were performed between annual loads of sediment and nutrients exported from the watersheds and a composite number that included either cropland distribution alone, or cropland distribution combined with the SVI. Coefficients of determination and p-values were compared to assess the ability of land use and SVI distributions to explain stream loads. Integrating the SVI in the land cover variable improved the ability to explain constituent loads in the watersheds for sediment, total nutrients, and dissolved nitrogen (N). Regression results with and without the SVI were identical for dissolved phosphorus (P), potentially indicating that SVI was not indicative of dissolved P transport at the current site. Overall, the application of the SVI at watershed scale was not perfect, but acceptable at correctly identifying cropland of greatest vulnerability and linking with transported constituent loads.
9pgs, Soil loss due to crop harvest contributes to land degradation, and knowledge of this challenge can guide the choice of crops for sustainable agriculture. Nigeria is the largest producer of cassava (Manihot esculenta Crantz) and the third largest producer of peanut (Arachis hypogaea Linn) in the world. Due to limited information on soil loss during peanut and cassava harvests worldwide, and cost of nutrient loss, a two-year field experiment was conducted to compare soil loss due to harvesting of peanut and cassava and to estimate cost of nutrient loss due to crop harvest under traditional agriculture. Peanut pod yields of 2.39 and 2.08 t ha–1harvest–1 removed 0.62 and 0.58 t ha–1 harvest–1 during peanut harvest, respectively, for years 1 and 2. Similarly, cassava yields of 22.71 and 21.40 t ha–1 harvest–1 removed 1.11 and 0.91 t ha–1harvest–1 during cassava harvest, respectively, for years 1 and 2. Crop yields strongly correlated with soil loss due to peanut harvest (R2= 0.36; p < 0.001) and soil loss due to cassava harvest (R2 = 0.23; p < 0.01). Significantly higher soil loss due to cassava harvest compared to peanut harvest can be ascribed to higher cassava yield. Also, soil nutrient loss due to crop harvest was significantly (p < 0.001) higher for cassava compared with peanut by 27.6% phosphorus (P) and 73.7% potassium (K) for the first year and 39.2% P and 79.1% K for the second year. Fertilizer equivalent cost of P and K losses due to cassava harvest for the two years was higher than that of peanut by US$29 ha–1. The study indicated that the intensity of nutrient loss by harvesting is largely dependent on the crop type, and harvesting of cassava can deplete soil nutrients faster than that of peanut under traditional agriculture. Sequential planting of cassava (deep rooted crop) followed by peanut (shallow rooted crop) as a crop rotation management practice is recommended to mitigate soil loss due to continuous harvesting of cassava, and harvesting with thorough shaking technique is also suggested to reduce nutrient loss potential of crop harvesting.
6 pages, via Online journal, Most agricultural soils are depleted of their soil organic matter (SOM) reserves. A severe loss of SOM content may degrade soil functionality, its capacity for provisioning of essential ecosystem services, and soil health. Therefore, restoration of SOM content in soils of agroecosystems may reverse the degradation trends, enhance ecosystem services (Banwart et al. 2015), and advance Sustainable Development Goals of the United Nations. (Lal et al. 2018a). Increase in SOM content may also partially replace the use of chemical fertilizers and supplemental irrigation, while restoring the environment.
8 pages, via online journal, Dense networks of rivers, canals, ditches, dikes, sluice gates, and compartmented fields have enabled the farms of the Red River Delta to produce 18% of Vietnam's rice (Oryza sativa) crop (figure 1), 26% of the country's vegetable crops, and 20% of capture and farmed aquaculture (Redfern et al. 2012). Agriculture in this fertile delta was transformed in the 11th and 13th century AD by large-scale hydraulic projects to protect the delta from flooding and saltwater intrusion, and provide field drainage during the wet season and crop irrigation in the dry season (Tinh 1999). The 20th century brought advancements in agricultural science globally—new crops and livestock genetics, inorganic fertilizers, mechanization, and pesticides that could double and triple food production per unit of land. It was the diesel pump combined with post-Vietnam War agricultural collectivization from 1975 to 1988 that brought the Green Revolution to the Red River Delta.
