10. Flood-tolerant crops for low-input sustainable agriculture in the everglades agricultural area.
J. of Sust. Agriculture, 2, (1), 1991, pp. 77-99
The objective of this paper is to describe potential crops for production in reflooded wetlands and present yield and resource use data (water, nitrogen, and phosphorus). The crops in the study include a tuber (taro, Colocasia esculenta), three grasses (alemangrass,
Echinochloa polystachia, flood tolerant sugarcane, Saccharum sp., and rice, Oryza sativa).
Wetlands have traditionally been viewed as wastelands; now vast areas of such lands have been converted to agricultural production worldwide.
This has often been done in the past without regard for potential environmental consequences or long term sustainability of agricultural production. Recently, wetlands have become appreciated for, among other things, their role in environmental quality and stability. This greater appreciation for wetlands, combined with extensive wetlands loss, has recently led to concerted efforts to protect these areas and, in some cases, has led to confrontations with agricultural interests.
Wetlands are often highly fertile when initially drained. This is the result of rapid oxidation of a soil which had accumulated in a flooded environment. During this oxidation process, nutrients which had accumulated in the soil organic matter over an extended period of time are released to the soil solution at a high rate. Eventually, the stocks of nutrients and soil organic matter are depleted, leading to poor native soil fertility, low agricultural production, and in some cases, abandonment of the now depleted wetland.
Studies of wetland cropping systems have been conducted at the Everglades Research and Education Center (EREC).
The crops in this study vary widely in yield and nutrient uptake. Rice, for example, thrives in water with very low phosphorus contents.
Alemangrass is a tremendous phosphorus sink, but may require supplemental phosphorus fertilization. Crops which thrive in oligotrophic conditions, as well as those which require large amounts of nutrients, are useful in water quality management. For example, alemangrass could be effective in reducing the phosphorus content of drainage from fields previously cultivated with crops which leave behind a large amount of fertilizer phosphorus, as do some vegetables. Rice can further reduce phosphorus contents to levels found under natural conditions. In addition, operating costs in a flood-tolerant cropping system may be lower for flooded crops because periodic flooding aids in the control of some pests and weeds.
Results from this study pertaining to crop management, water and nutrient budgets are encouraging. More information is neded about soil formation and nutrient dynamics in a flood-tolerant system. For example, the balance between soil formation and soil loss for the crops in this study is not well understood. A desirable feature of flood-tolerant crops may be a reduction in nitrogen and phosphorus fertilization over that required by upland crops, however, nutrient mineralization rates and availability to crops when fields are flooded for long periods of time are not well understood in the EAA either.
Economic viability is a complex topic as well.
Currently, upland crops are profitable to the extent that it is not economically sensible to make meaningful investments in soil conservation.
Successful expansion of wetland agriculture in the EAA imlies reversal of soil loss, reduction of nutrient levels in drainage, compatibility with natural hydrologic cycles, and economic viability. Long term sustainability has been experienced in similar systems in other parts of the world. For example, it has been reported that aquatic crops have been grown for more than 400 years in the same organic soil without fertilization in Malaysia.
The development in the Everglades Agricultural Area (EAA) of sustainable agriculture in a former wetland can serve as a model for the many countries which have undertaken or contemplated wetland conversion.
Indonesia, for example, is draining parts of 27 million ha of organic soils, much of it along coastal areas.
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Review, book, tropics, crop production, environmental factors, plant population density, crop productivity, physiological process, CAB, ODA
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