Eggplant: Role of this Warm Season Vegetable in Conservation Planning
Rani G. Kumar, Girish K. Panicker* and Franklin O. Chukwuma Eggplant or brinjal (Solanum melongena L.), also called garden egg, aubergine, patlican and melanzana, belong to the family of Solanaceae (nightshade) and is a native of southern India. This family includes the prominent vegetable crops such as potato, tomato, and peppers. Fruits of these tender, herbaceous, perennial, shrubby or bushy plants are commonly cultivated as annual vegetables for their nutritious fruits. The Spaniards brought this hot weather, cold-sensitive crop to the Americas. Purposes
To conserve soil and water through the use of vegetation To maintain and/or to improve soil availability, quality, and soil nutrients To suppress weeds, reduce insect pests and diseases, and increase crop yield To improve soil tilth, soil organic matter, and soil structure
Planting: Eggplant can be planted straight or as transplants (transplant must be hardened up to 8 to 10 wks). It is a heavy feeder and fairly self-fertile. For best yields, well-drained, composted, deep, sandy loams or loam soil, raised beds, sunny and sheltered location, a pH between 6.0 and 6.8, growing temperatures 70 to 85 F (daytime) and 64 to 70 F (night) are needed. Previously lime mixed soil, added with sufficient compost/manure, and an all-purpose garden fertilizer like 10-10-10, will advance the crop growth. Plant in twin rows 18 to 36 inches between plants with rows 4 to 5 feet apart. 2 to 3 weeks old plants must be supported with stakes. Weekly, an inch of water is vital to guarantee uniform growth and fruit enlargement. Extensive dry periods demand irrigation for even production. Flowers are generally pollinated mechanically or by wind or wild bees. Staking eggplants (2 to 3 weeks old) result in steady growth and persistent production.
2 Nearly all varieties are ready to harvest after 70 to 80 days, when the fruit reaches a desirable size (5-6 inches). Crop Rotation is an important cultural strategy broadly used for the long term success in farming. Crops are mainly rotated to limit the agricultural pest populations, diseases and weeds when the same garden site is used, continually. This economical, defensive measure improves soil biological activity, tilth and soil organic matter content, structure, nutrient demands, water-holding capacity and fertility, profitably. Rotations stabilize and minimize fertilizer use by decreasing the risk of weather damage and increasing the yield. In a planned vegetable garden, botanically dissimilar crops are rotated: for instance, solanaceous crops or the nightshade family are avoided after eggplant, for minimum 2 years. Egg plants are preceded by crops like lettuce and cut flowers and succeeded by crops such as okra, melons, squashes and cucumbers. Cover crops are green manure crops grown generally for continuing productivity and for enhancing soil physical properties. Organic farmers take advantage of its nutrient management capabilities. Cover crops cover and preserve top soil, supply organic matter and soil tilth, offer plant cover and aeration, boost biodiversity, suppress weeds and soilborne diseases, diminish compaction, leaching, wind and water erosion, and are plowed down (before getting matured) to fertilize soils or used as surface mulch. A mixture of cover crops is strong enough to eliminate nutrient losses and soil erosion. Hairy vetch is a useful cover crop that adds high level of organic matter for the yields of eggplant. Green manure intercropping or pre-cropping will uphold soil quality and offer eggplants additional N for dynamic growth. Mulching is the beneficial practice of spreading a defensive layer of organic (leaf mold, lawn clippings, bark chips, sawdust, straw, peat moss, compost etc) or inorganic (plastic, stones, gravel, brick chips etc) substance on top of the soil, in uneven thickness. This process retains uniform moisture, conserves water, adds nutrients, stimulates topsoil microorganisms, aids in weed control and reduces erosion, soil compaction and fertilizer application. Vegetables like eggplant need summer mulches that should be applied only when the soil is warmed. Summer mulches systematize soil temperatures and suppress weeds. Organic mulches have the benefit of rotting fast and constantly supplying organic matter to the soil, improving fertility, structure and healthy growth. Usage of plastic mulch in eggplant production doubles the number of fruits by keeping the soil warm and lessening fertilizer leaching and offering plentiful crops. Pest and Weed Control: Eggplants are commonly attacked by insects like aphids, corn earworms, hornworms, spider mites, pirate bugs, tarnished plant bugs, leaf-footed bugs, stink bugs, thrips, Colorado potato beetles and flea beetles. Raising diverse, non-related crops in the farm will deject insects and disease pathogens. Thrips can be suppressed with biological insecticides like Beauveria bassiana. Black plastic mulches, floating row
3 covers, insect-exclusion covers, hot pepper extract spray and wax are good defenses against Verticillium wilt disease and insect pests. Deep turning, litter destruction, rotation and planting grass in between rows remove Southern stem blight. Cultivating on raised beds, companion planting with Marigolds, basil, lettuce and fennell are helpful for suppressing collar rot. Sunny location, shallow cultivation, cover crops, hand weeding, sanitation, usage of resistant varieties, avoidance of over watering, weekly scouting etc. are helpful cultural control practices. Use chemical control for critical damages. Disking is a recognized practice globally used in agriculture, before planting the main crop. This procedure eliminates unwanted vegetation and weeds, loosens the soil and incorporates old crop residues, makes fine and uniform seed bed, and evades soil compaction and enhances deeper rooting, production and harvest. In eggplant production, land should be disked systematically (least eight inches deep) several weeks before transplanting. Drawbacks of disking include dust, soil disturbance, compaction and erosion, limited root development, crop residue loss, decrease in the yield, and expenditure for machines and labor. Residue Management is a valuable technology which has been very successfully applied on farmlands, to increase productivity. Crop residue retains soil moisture and nutrients, prevents soil crusting and erosion, helps root breath freely, influences root development, improves soil structure, creates a favorable environment for soil microbes, and lastly, improves soil physical and chemical properties. Surface residue management is the most promising and practical erosion control practice today. Conservation research conducted with low density and high density planting systems shows that high plant density produces taller plants and canopies, and their root system grows deeper and wider in the soil. High plant density increases competition for light, water, and nutrients, resulting in a lower yield, but builds drier biomass than low density planting. Eggplant creates drier biomass than the minimum quantity of residue recommended by the Natural Resources Conservation Service for erosion control. Low density makes more leaf area per unit of ground area (leaf area index) until 80 days of growth, but the leaf area goes higher in high density planting after 80 days and it continues until the final harvest. The yield reported on low density planting is also higher with longer and thicker fruits than the high density. Low population densities have less competition for water, light, and nutrients, which may result in better yields with quality fruits, even though this system faces problems from increased weed growth. The yields reported are 14,550 lb/acre for low density and 11,700 lb/acre for high density planting. After the final harvest, the eggplant returns 1650 to 1750 lbs/acre of dry biomass, which contains 36% carbon and 1.96% nitrogen. This crop returns an average of 600 to 630 lbs/acre of carbon and 30 to 35 lbs/acre of nitrogen. ______________________________________________________________________________________ Published by Cooperative Extension, School of Agriculture, Research, Extension, and Applied Sciences, Alcorn State University, Mississippi, in collaboration with the USDA/NRCS. Alcorn State University is deeply grateful to the USDA/NRCS for providing funds for this publication. *Corresponding author.