Comparison of soil quality of farms managed with sustainable and conventional soil management practices in Oklahoma

View the project final report

• 2011 annual report

Commodities

• Agronomic: canola, cotton, sorghum (milo), grass (misc. perennial), hay

Practices

• Animal Production: manure management, preventive practices, feed/forage
• Crop Production: no-till, application rate management
• Education and Training: decision support system, display, extension, on-farm/ranch research, workshop, technical assistance
• Natural Resources/Environment: carbon sequestration, indicators, soil stabilization
• Production Systems: holistic management
• Soil Management: organic matter, soil analysis, composting, soil chemistry, soil quality/health
• Sustainable Communities: sustainability measures

We initiated an on-farm project to generate local soil quality information comparing soil quality of sustainable and non-sustainable systems, and develop soil quality assessment index and online tool. We collected soil physical, chemical and biological properties in spring and summer 2011 from 63 farms. In about 65% of the fields we sampled, the owners participated in sampling and person-to-person discussion of the results we found. Overall, growers were optimistic and showed interest to use on-site soil quality measurements. We conducted two in-service trainings in 2011 and provided three presentations and demonstrations as part of a series of composting and rainwater harvesting workshops took place in May 2012.

Introduction

There are documented reports that showed conventional farming systems are associated with a decline in soil quality (Pang and Letey, 2000; Logsdon et al., 1993; McGarry et al., 2000). According to Logsdon et al. (1993) and McGarry et al. (2000) conventional soil management practices such as use of inorganic fertilizers with monocropping resulted in poor soil structure and aggregation, and an increase in soil bulk density, soil salinity, nitrogen leaching and ground water contamination. A research conducted in California that compared 13 pairs of organic (utilize ecological based soil management) and conventional strawberry agroecosystems confirmed that soil quality in organic strawberry was way better than conventional agroecosystems (Reganold et al., 2010). According to these authors, total carbon and nitrogen were 21.6 and 30.2% more in organically managed surface soils compared to their conventional counterparts. In Oklahoma, neglect of indigenous knowledge systems and farming culture has resulted in reduction of farm crop diversity and soil degradation since the 1940s. In 1945, there were 4.6 crop commodities per farm. These were reduced to 1.2 by 2002 (McDermott et al., 2006). Along this, monocropping, erosion, residue removal and excess fertilizer use for the limited commodities grown in the state resulted in poor soil quality. Soil pH in Oklahoma soils was reduced due to application of ammonia based fertilizers with poor efficiency of use (Raun and Johnson, 1999), and continuous mining of basic cations with harvested yield. Fertilizer use efficiency, particularly nitrogen in cereals is estimated to be 33 to 45% despite increased yield obtained due to fertilization (Raun and Johnson, 1999). This suggests that more than 50% of applied fertilizer could either leach into the ground, drain to water bodies or go back to the atmosphere as greenhouse gases causing environmental pollution. Oklahoma soils are very low in soil organic matter partly attributed to conventional soil and crop production practices. It was documented that Oklahoma lost 62,752,791 tons of organic carbon to agriculture (OCC, 2003) since the 1940s. In fact studies showed that organic matter was reduced to <1.1% from its original 4.0% due to continuous cropping and conventional tillage following the conversion of grassland to continuous crop production (Boman et al., 1996; Girma et al., 2007). Given the fact that soil quality is the basis for sustainable production system (Wander et al., 2002), due emphasis must be given for improving and monitoring soil quality. But locally documented information, technical skill and practical models (Middendorf, 2007) are lacking. Also, the shift to a more sustainable soil management system remained slow because of lack of data and education in Oklahoma. To address these problems, it is necessary to integrate the different soil components together to evaluate changes in soil quality in time and space. This can be achieved with the use of indices (Granatstein and Bezdicek, 1992; Doran and Parkin, 1994). An index must be adaptable to local or regional conditions. Suitable reference points and optimum ranges are needed for soil quality components (Girma, 2009).

(1)   Generate local soil quality information comparing soil quality of sustainable and non-sustainable systems ,

(2)  develop soil quality assessment index that can be used to quantify overall soil quality status of a farm , and

(3)  develop an online soil quality assessment decision aide program.