Reji P. Mathew Abstract

Reji P. Mathew Abstract
Assessment of Yield and Soil Quality in a Transitional Organic Farming System
By Reji P. Mathew
Advisor: Dr. K.  Kpomblekou-A


According to USDA, the retail sales value of organic foods was $7.05 billion in 2001 and is projected to reach $20 billion by 2005 in the U. S. Health conscious consumers, who have made food safety an issue of high priority, primarily drive this increase in organic food business. The Southeast is lagging behind in terms of consumer demand for organically grown foods. Research to support and increase public awareness of organic agriculture is slow to meet consumers’ demand for organic foods. Although in recent years the number of land-grant 1862 institutions that provide research and resources to support organic farming has grown, research to support organic farming at land-grant 1890 institutions is almost nonexistent. Out of thirteen 1890 universities surveyed only two universities: Fort Valley State University and Kentucky State University have active organic farming research plots. A field study was initiated in spring 2001 at Tuskegee University to investigate the use of organic fertilizers as sources of nutrients with the goal of safe and secure production of vegetables. The objectives of this study are to evaluate yields of different cultivars of sweet potato using organic fertilizers and to determine the impacts of organic farming practices on soil quality. Research plots were established at George Washington Carver Agriculture Experiment Station in 2002.  The experimental design is a randomized-complete-block of four replications and four treatments (control, commercial NPK fertilizer, broiler litter, and clover amendments) examining three cultivars (606258, ASP-12.6, and Beauregard) and organic fertilization. To homogenize the soil in the experimental field, Crimson clover was planted in December 2001 and harvested and incorporated into soil in May 2002. Prior to establishment of the experimental plots (20’ x 12’), soil core samples were taken from 0-15 cm depth. The soil samples were air-dried and ground to pass through a 20–mesh or an 80-mesh sieve for determination of chemical properties. At the end of the cropping season, sweet potato yield was measured and soil samples were collected in the upper 0-15 cm horizon at incremental depths: 0-1, 1-2, 2-3, 3-5, 5-10, and 10-15 cm. Sodium hexametaphosphate solution was used to disperse the soil aggregates; the samples were then wet sieved to separate three fractions of particulate organic matter (coarse: 4000-2000; medium: 2000-250 and fine 250-53 µm) and an organo-mineral fraction (53-20 µm). Organic C, N, and S in each fraction were determined by using a high-temperature-combustion Auto Analyzer Vario EL III CHNS (Elementar Americas, Inc. NJ).  Preliminary results showed that sweetpotato yields varied with cultivars and soil amendments. Average yield of “606258” cultivar grown in broiler litter-amended plots, Crimson clover-amended plots, NPK fertilized plots and control plots without fertilizer were: 7.14, 7.29, 7.10 and 7.04 t ha-1, respectively.