This study conducted on a Memphis silt loam at Alcorn State University in 1993 and 1994 investigated the influence of conventional (chemical-intensive) monocropping system, transitional (reduced-chemical) and organic (non-chemical) farming systems on the yield potential of "Marion" tomato cultivar and soil characteristics. Estimated costs and returns for the production of tomatoes and its companion crops were also investigated. Fruit number and weight were highest with the conventional farming system. Fruit size was highest for the conventional and transitional farming systems. Soil nitrate-nitrogen was highest with the conventional farming system, whereas orthophosphate and soil acidity were highest for both conventional and transitional farming systems. Soil organic matter was highest with the transitional and organic farming systems in 1993 but not different in 1994. Plant growth was highest with the conventional farming system. Soil extractable nutrients were generally highest due to transitional and organic farming systems. Profitability from tomato sales was highest for the conventional farming system, however with the addition of profits generated from the sale of the companion crops, the overall profits from the three farming systems were comparable. Adoption of a sustainable vegetable production system in Mississippi could among other benefits lead to the reduction in environmental damage from agriculture chemicals.

An urgent challenge facing agricultural scientists working on highly erosive soils in Mississippi is the need to find viable, sustainable and environmentally sound alternatives to the current chemical-intensive, monocropping systems. The need to maintain sustainability and to reduce production costs associated with purchased inputs has heightened interest in alternative farming systems.

Low-input agriculture is generally more environmentally benign than conventional, petrochemical-based systems and offers a potentially attractive means for improving the environmental performance of American agriculture and avoiding inevitable confrontations between farmers and Environmental Regulatory Agencies (Edward et al., 1990). Crop yields from low-input farming systems might actually exceed those of conventional cash grain farmers during periods of below average rainfall (USDA, 1980). Maize yields increased by 16 to 17 percent when grown after soybeans compared to continuous maize (Randall, 1981). Yields were also higher following two years of alfalfa compared to continuous maize. This was consistent with zero to 180 kg of nitrogen per hectare (Adams et al., 1974).

Intercropping of low-growing cover crops, referred to as "living mulch" is an alternative method of weed control in conventional and reduced tillage systems that may also reduce dependence on herbicide (Lal, 1975). Mulch crops like rye, have traditionally been planted to compete with weeds, cover the soil in winter, and improve soil tilth when they are plowed or disked in the spring (Regnier and Janke, 1990). In addition to physical weed suppression from mulch, many plant species such as vetch, clover, wheat, and rye contain allelochemicals that suppress weeds and other plants.

Intercropping of two harvested crops is used extensively in the tropics to maximize land use and to ensure against crop failure (Mercado, 1987). In New Jersey, Prostko and Linicki (1988) reported that in a barley-soybean relay-intercropping system, the intercropped system with no herbicide provided 70 to 93 percent control of fall panicum, red root pigweed, and giant ragweed, and resulted in soybean yields comparable to the intercropped system with herbicides. In a companion vegetable garden, culinary herbs can repel insects, add flavor, and improve the growth of the vegetables which they are near (Sheryl, 1981).

Reichelder and Bender (1979) reported that the economic performance of the farm can change significantly during a multi-year change from conventional to alternative practices. Also, Dabbert and Madden (1986) concluded with a whole-farm budget approach that, although crop rotations will generally increase yields and decrease production cost, the full impact of crop rotation will take several years to materialize.

Developing low-input sustainable vegetable production systems in Mississippi could improve the profitability of farming operations, minimize fluctuation of farm income, reduce soil loss from water and wind erosion, and enhance the economic well-being and quality of life of farmers and rural communities.

The Sustainable Agriculture program at Alcorn State University is designed to investigate alternative sustainable production systems for small vegetable and fruit producers in southwest Mississippi. The specific objectives of this study are: (1) to determine the effect of sustainable vegetable production on some properties of the soil; (2) to determine the growth, yield potential, and the nutritional quality of vegetable crops grown in sustainable farming systems; (3) to compare costs and returns for vegetables produced in sustainable agricultural systems with those of conventional methods.

A field experiment was used in the summers of 1993 and 1994 to compare agriculture sustainability of conventional (chemical-intensive) monocropping system, transitional (reduced-chemical) and organic (non-chemical) farming systems. Tomatoes (Lycopersicon esculentum) grown in a 3-year rotation with field peas (Vigna sinensis) and collards (Brassica oleracea) were used in this study. These experiments were conducted on a Memphis silt loam soil (Typic Hapludalfs: fine silty, mixed thermic), at the Alcorn Experiment Station. Extractable nutrient levels from these plots which were under fallow for 3 years before the initiation of this study were low for potassium (208 kg/ha), high for calcium (3,438 kg/ha) and phosphorus (87 kg/ha), very high for magnesium (763 kg/ha) and zinc (5 kg/ha). Soil pH was 5.8. A randomized complete block experiment design was used, with four replications of each farming system (treatment). Each block was separated on all sides by an uncultivated alley 3 m wide to prevent possible overlapping of the effects of the different farming systems. Moisture application was by natural rainfall supplemented as needed by drip irrigation. Methods for field preparation, fertilization, and pest management varied with the farming system. Fungicide was applied to the conventional farming system only.

Conventional Farming System--A tractor was used for field disking (3 times) and row preparation. Crops were planted in rows 6.1 m long and 1.07 m wide. Fertilization with 134.4 kg/ha, each of anhydrous ammonia, triple superphosphate, and muriate of potash was based on soil test result. Half the nitrogen level was applied at land preparation with the full levels of phosphorus and potassium. The second application of nitrogen was at fruit formation. Single applications of Dacthal® and Poast® were made at the rates of 24.39 kg ai/ha and 3.69 kg ai/ha, as preemergence and postemergence herbicides, respectively. Thiodan® was applied at the rate of 4.61 L/ha for insect control, and Maneb® was applied at the rate of 2.23 kg/ha for disease control. Both applications which began two weeks after transplanting were made biweekly throughout the growing season.

Transitional Farming System--Tomato production was achieved by a combination of off-farm and on-farm resources. This farming system protects against some pitfalls such as initial decrease in income, associated with switching directly to organic agriculture. It also used crop rotation, companion planting and mulching to substitute for the reduction in chemical fertilization and pesticide application. Tillage was limited to disking (2 times) and row preparation. Tomatoes (test crop) were intercropped with peppers (Capsicum frutescens) while the rotational crops, field peas and collards, were intercropped with radish (Raphanus sativus), and swiss chard (Beta vulgaris), respectively. Fertilization was with 13.4 kg/ha each of urea, simple superphosphate, and potash. Applications were as for the conventional monocropping system. Rows were mulched with pine needle or black plastic for weed control. A single application of Poast® was made at the rate of 3.69 kg ai/ha. Diatomaceous earth was applied at the rate of 11.2 kg/ha for insect control by dusting with "Dust Mizer" or "Midget Garden Duster."

Organic Farming System--Tomato production was achieved by both on-farm and off-farm resources. Tillage was limited to disking (1 time) and row preparation. Tomatoes were intercropped with sweet basil (Ocimum basilicum), field peas with catnip (Nepeta cataria), and collards with mint (Mentha species) herb companions. Intercropping with herbs could mean a reduction on the risk of test crop loss, repulsion of insects that damage the crops, and enhancing test crop productivity. Fertilization was with 975.74 kg/ha of organic nitrogen (from leather tankage), 875.74 kg/ha of soft rock phosphate, and 341.51 kg/ha of sul-po-mag. Applications were made during field preparation as recommended. Rows were mulched with pine needle or black plastic for weed control. Diatomaceous earth application for insect control was the same as the transitional farming system.

Sustainability of agriculture was based on the state of soil resources, plant growth, yield, fruit quality, and profitability. Soil samples collected at soil depth of 0.20 cm from each block at the end of the growing season were analyzed for available nutrients, organic matter, acidity, cation exchange capacity, nitrate-nitrogen, and orthophosphate. Plant growth was determined by plant height and shoot dry weights. Yield was determined by fruit size, number and weight per plant, and fruit quality by mineral composition and fruit dry matter. Both field peas and collards used either in a 3-year rotation with "Marion" tomatoes under transitional and organic farming systems or grown under the conventional, monocropping system were also evaluated for yield potentials and nutritive qualities (data not presented). However, additional harvests from the companion vegetable (hot pepper) and herb (sweet basil) were used to determine the overall profitability of the transitional and organic farming systems.

All input requirements for the three farming systems were identified. Labor and other factors of production were measured for each production enterprise. Data were analyzed by analysis of variance and means separated by Fisher's least significant difference (LSD) test (Steel and Torrie, 1980). Summary of estimated costs and returns were used to compare the relative profitability of each farming system.

The effect of each farming system on tomato yield is reported in Table 1. In 1993, the highest marketable tomato number per plant and tomato weight per plant were with the conventional farming system. Marketable fruit dry matter was highest with the organic farming system. The conventional farming system produced the highest overall (marketable and nonmarketable) number and weight of tomatoes per plant for the 1993 growing season. The overall Fruit size was highest with the conventional and transitional farming systems.

In 1994 (Table 2), the highest marketable tomato number and weight per plant and the highest overall fruit number and weight per plant were due to conventional farming system. Marketable fruit dry matter was highest for the organic and transitional farming systems. The overall fruit size was not affected by farming system. Reduction in marketable fruit number per plant due to the conventional farming system in 1994 could among other factors be due to the reduced number of harvests. The number of harvests for the 1993 and 1994 growing seasons were 13 and 8 times, respectively. Plants stopped producing marketable fruits earlier in 1994 due to dry weather conditions. Data showed that in 1993 more marketable fruits were harvested later in the season from the conventional farming system. Marketable tomatoes were red-ripe, disease and insect free and large enough for fresh-market sale by commercial tomato growers.

Pine needle mulch used in the 1993 management practice for the transitional and organic farming systems was replaced with 4-mil black plastic mulch in 1994. Early season disease infestation was a problem in 1993, but not a problem in 1994. The change in mulch and decrease in disease both contributed to the increase in marketable and overall tomato yield in 1994 for the transitional and organic farming systems. Organic fungicides may also be used for better disease control.

In 1993, plant height and shoot dry weight were highest (1.57 m and 0.33 kg/plant), respectively with the conventional farming system. In 1994, plant height was also highest (1.72 m) with the conventional farming system. The shoot dry weight was nonsignificantly highest (0.26 kg/plant) with the same farming system (data not presented). In 1993, fruit mineral composition was not different except for K and Ca. The respective highest values of 4.41 and 6.98 mg/g were with the transitional farming system. In 1994, fruit K, Fe, Zn, and Mo were highest (7.05, 0.90, 0.42, and 3.23%), respectively with the organic farming system (data not presented).

The effect of each farming system on soil characteristics is reported in Table 3. In 1993, soil nitrate-nitrogen, orthophosphate, organic matter and soil acidity were influenced by the type of farming system. Nitrate-nitrogen value was highest (24.40 mg/kg) with the conventional farming system. There was no difference in soil pH or orthophosphate levels between the conventional farming system and the transitional farming system or in soil organic matter content between the transitional farming system and the organic farming system.

Table 1. Effect of farming system on yield, dry matter, and size of "Marion" tomato at Alcorn Experiment Station, Lorman, MS 39096 (1993).

XData are average of 13 harvests for the 1993 growing season.

YOverall yields include nonmarketable fruits (severely cracked, diseased, insect damaged and green tomatoes) and marketable fruits (red-ripe, disease and insect free, and large enough for fresh-market sale by a commercial tomato grower).

Table 2. Effect of farming system on yield, dry matter, and size of "Marion" tomato at Alcorn Experiment Station, Lorman, MS 39096 (1994).

XData are average of 8 harvests for the 1994 growing season.

YOverall yields include marketable, severely cracked, diseased, insect damaged and green tomatoes.

Table 3. Effect of farming system on soil nitrate-nitrogen, orthophosphate, organic matter, cation exchange capacity and soil acidity, 1993X.

XSoil samples collected at soil depth of 0-20 cm from each block at the end of each growing season were used for analysis.

Table 4. Effect of farming system on soil nitrate-nitrogen, orthophosphate, organic matter, cation exchange capacity and soil acidity, 1994X.

XSoil samples collected at soil depth of 0-20 cm from each block at the end of each growing season were used for analysis.

In 1994, soil nitrate-nitrogen was highest (12.80 mg/kg) with the conventional farming system (Table 4). Orthophosphate was higher for the conventional and transitional farming systems than for the organic farming system. Soil organic matter, cation exchange capacity, and soil acidity were not affected by the type of farming system. The significant reduction in soil nitrate and orthophosphate for the organic farming system in 1993 and 1994 indicates a lesser chance for surface and/or ground water contamination by this farming system as compared to the conventional and transitional farming systems.

The summary of estimated costs and returns for the production of tomatoes and companion crops is reported in Table 5. Cost for the purchase of farming materials such as fertilizers, herbicides, insecticides, fungicides, mulching materials, and metal stakes was highest for the organic farming system. Labor cost was highest for the conventional farming system. Profitability from tomato sales was highest for the conventional farming system as compared to transitional and organic farming systems because of the significant increase in marketable tomatoes for this farming system. However, sales from the vegetable companion (hot pepper) and herb companion (sweet basil) generated additional profits of $96.10 and $180.40 from a 26.01 sq m area for the transitional and organic farming systems, respectively. The overall profitability from the transitional and organic farming systems were therefore comparable to that from the conventional farming system. Additional income could be generated from tomato sales from the alternative farming systems if pests were adequately controlled, purchased off-farm resources significantly reduced, and unit price for organically-grown tomatoes increased.

Table 5. Summary of estimated costs and returns, 1993 and 1994X.

XEstimates for the 2-year study were based on the average cost for a 26.01 sq m of the experimental area.

YPrices per kilogram were based on sales average from 5 local supermarkets.

Findings from this study suggest that: (1) the conventional farming system encouraged greater "Marion" tomato cultivar growth and productivity than the transitional and organic farming systems; (2) although marketable tomato yields were much lower, profitability from transitional and organic farming systems are comparable to the conventional farming system, when additional profits from the sale of their companion crops are considered; (3) transitional and organic farming systems generally favored fruit mineral composition more than conventional farming systems and had much lower soil nitrate-nitrogen levels which should lower surface water contamination; (4) adoption of a sustainable vegetable production system in Mississippi could lead to a reduction in environmental damage from agricultural chemicals and an enhancement of the quality of life of farmers and consumers. Consumers must be willing to pay more for vegetables grown in a sustainable farming system in order for sustainable vegetable production to become standard practice.

The authors wish to thank USDA-CSREES for funding this study under the Capacity Building Grants Program. Grateful appreciations are extended to Dr. Rudolph Waters, Interim-President, Alcorn State University, and Dr. Leroy Davis, Dean of AREAS, Alcorn State University, for supporting the study. Thanks are also extended to Larry Russell, Joseph Jackson, Cornelious Davis, and James Hyche for assisting with field activities, and to Janice Carter for typing the manuscript.

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