Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/20/2014
Publication Date: 3/3/2014
Citation: Kremer, R.J., Deichman, L. 2014. Soil quality and the solar corridor crop system. Agronomy Journal. 106:1853-1858. DOI: 10.2134/agronj13.0508. Interpretive Summary: Increased demands for plant-based products require that land for growing crops be used more efficiently. Modern crop production is typically managed as single crops planted in large-scale fields, or monocultures. Production relies on inputs of chemical fertilizers and pesticides and limited tillage, potentially contributing to soil organic matter loss and reduced surface and ground water quality. Innovative cropping systems are needed to overcome potential soil productivity and environmental consequences associated with monoculture crop production. The solar corridor crop system (SCCS) is an alternative that increases crop diversity by intercropping with different species within the same field. The main feature of the SCCS is use of wide row widths that allows full exposure of tall crops such as corn to sunlight. Based on older studies with corn at the edge of fields where the same effect occurs, the greater exposure to light improves photosynthesis, which provides more carbon for grain development. However, essentially no quantitative information exists on soil quality status in the SCCS compared with monoculture crops. Soil quality is the ability of a soil to function under managed conditions to sustain biological productivity, promote plant and animal health and maintain environmental quality. Our research objective was to assess soil quality in the SCCS planted to corn with wheat intercropped in the corridors relative to a monoculture system. Soil from fields planted in wide rows (the solar corridor) showed equivalent amounts of biologically available carbon and levels of biological activity as did soils from monoculture corn under the same plant population density. As the growing season progressed, biological activity in the solar corridor corn increased by 50% compared to monoculture corn, suggesting that better sunlight capture in the corridors led to more carbon trapped by corn, higher release of carbon compounds into soil, and stimulation of soil microbial activity. Soil active carbon (available to microbes) and soil microbial activity are important indicators of soil quality. Based on the results of this limited study showing the benefits of the SCCS in enhancing attributes of soil quality, more controlled research trials in several locations are necessary to quantitatively document that the SCCS can be an effective alternative crop management system beneficial to soil properties. Results obtained from such research are important to researchers and farmers pursuing sustainable agricultural production programs.
Technical Abstract: The solar corridor crop system (SCCS) is designed for improved crop productivity based on highly efficient use of solar radiation by integrating row crops with drilled or solid-seeded crops in broad strips (corridors) that also facilitate establishment of cover crops for year-round soil cover. The SCCS is an agroecosystem with diverse system structure that should inherently provide many features to build soil quality. Management strategies include reduced tillage, intercropping, and soil conservation through crop residue retention, which can improve soil quality properties including soil organic C and N, nutrient cycling, and microbial activity. Our objective was to evaluate the effect of a corn SCCS planted in 152-cm (corridor) row widths compared with corn monoculture in 76-cm row widths on soil quality using selected indicators of soil quality . Microbial activity, measured as soil glucosidase activity, was highest in rhizosphere soils under corn hybrids at 74,000 plants ha-1 regardless of row width. However, soil glucosidase activity was strongly correlated (r2=0.72) with active carbon, which increased in rows bordering the corridor. This suggested that increased carbon fixation by plants at the wide row width due to greater exposure to solar radiation also increased carbon substrates released into the rhizosphere for microbial metabolism. The limited soil quality assessment conducted in this study suggested that an integrated cropping system represented by the SCCS offers an effective management system for maintaining crop production while promoting soil quality and soil conservation.