Sound Soil Management for Papaya: Case Study of the North of Espirito Santo, Brazil

Agriculture and cattle husbandry as practiced in North of Espirito Santo State is an unsustainable model of food production due to inadequate soil management. Several factors such as monoculture, clean-cultivated orchard, intensive mechanization and inappropriate use of chemicals and irrigation lead to a nonproductive agro-ecosystem. Papaya cultivation, for instance, causes great impact on soil structure due to heavy traffic for harvesting, chemical applications, and other cultural operations. Also, traditional growers use plowing for land preparation and weed control create plow sole, which impairs water penetration into the subsoil. Indeed, uncovered soil after plowing the beating force of a raindrop may disaggregate soil particles and globules of mud are hurled in all directions initiating the erosion process. Yet inappropriate center pivot irrigation system common in the region accelerated soil degradation. Although the reduction of the productive capacity of soils through the loss of fertility and structure is considerable, the most serious problem is erosion. Nutrients can be added by fertilization, but the loss of topsoil cannot be so easily or quickly remedied. To cope with this scenario, the following sound practice has been suggested: (1) Site selection (edaphic condition) for orchard establishment is determinant for economically and environmentally sustainable production. Papaya trees fare best in deep, well-aerated sandy loam soils. (2) Use of minimum tillage system for land preparation. (3) Sod culture with grass mowed periodically with rotary mower that move the cutting grass down the papaya rows as mulch and maintain a vegetative cover within the row which retards erosion by breaking and cushioning the beating force of the rain and increasing the absorptive capacity of the soil. Mulching may improve soil biological activity since organic matter and microorganisms establish a favorable carbon balance in the soil for productivity maintenance. (4) Add 5 to 7 t/ha of organic compost being 60% in the establishment and 40% three months after transplanting (sexing time). Organic matter has a number of advantages: a) increases water-holding capacity; b) readily permits the infiltration of water; c) is a source of mineral elements; d) it may retain large quantities of minerals, thus preventing their loss from the soil by leaching. (5) Drip irrigation system to deliver water daily (two to four pulses during day time) to replenish loss by transpiration and evaporation from the soil surface. (6) Control of chemical soil dispersion caused by high Na: Ca ratio in the irrigation water by systematic application of calcium into the soil is also an important decision. (7) Tractors with wide tires moving on alternate rows by using 50% of the area may help on reducing hardpan during period of high traffic in the orchard. All suggested sound management has been successfully implemented by farmers in North of Espirito Santo which has drastically reduced soil erosion and maintained soil fertility and yield with high quality papaya.