Soil Acidity (Al) Impact on Nutrient Use Efficiency and Yield Sustainability of Crops.
Virupax Baligar, USDA-ARS-SPCL-BARC-West, Bldg 001, Room 225, 10300 Baltimore Av, Beltsville, MD 20705-2350 and Nand K. Fageria, EMBRAPA National Rice and Bean Center, Cx Postal 179, Sto Antonio de Goias, GO, 7537500, Brazil.
Soil acidity is the main constraints for crop production in various parts of the world. It is estimated that about 4 billion ha of land area of the world is affected by acidity. In addition, a large part of the world population makes their living on these marginal soils. Hence, improving crop productivity on these soils is vital for social-economical reasons. The main reasons for low crop productivity on acid soils are nutrient deficiency and elemental toxicity. Application of adequate rate of fertilizers and liming are important strategies for improving crop yields on acid soils. Nutrient recovery efficiency by plants is less than 50% for N, and K and less than 10% for P and micronutrients. The low nutrient recovery efficiency is associated with loss of nutrient by volatilization, leaching, denitrification, soil erosion, and plant canopy. Furthermore, in acid soils low nutrient recovery efficiency is also associated with Al/H ion toxicity, immobilization of some nutrients such as P and low microbial activity. These low nutrient recovery efficiencies not only increase cost of crop production but also create environmental pollution problem. Hence, improving Nutrient Use Efficiency (NUE) on acid soils is desirable to improve crop yields, reducing cost of production, and maintaining environmental quality. The NUE in acid soils can be improved by using adequate rate of liming, and other fertilizer management practices. However, resource poor farmers in developing countries can not apply adequate rate of lime as well as fertilizers. Hence, under these situations, use of limited amount of lime and fertilizers along with nutrient efficient and elemental toxicity resistant plant species or genotypes within species is a complimentary solution for improving crop productivity on acid soils. Plantation crops such as cacao, rubber, oilpalm, coffee, papya and banana in conjugation with row crops make an important ecosystem on acid soils in the developing countries of the tropics. Genetic differences in plant species or genotypes within species have been widely reported. Inter-and intra- specific variation for plant growth and NUE are known to be under genetic and physiological control and are modified by plant interactions with environmental variables. Genetic and physiological components of plants have profound effects on the ability of plants to acquire, transport, and utilize absorbed nutrients under various environmental and ecological conditions. To enhance the crop yield potentials of plants grown on acid soils, increase in NUE (acquisition, influx, transport, utilization, remobilization) and growth parameters (plant demand, root morphology) and plants ability to interact effectively with environmental variables (drought, solar radiation, temperature extremes, soil acidity) are needed. The emerging era of adapting the plant to the natural environment is paramount to stabilizing crop yields and world food security for the future. The key to this effort will be breeding cultivars with high NUE and tolerant to abiotic stresses. Recent findings have shown the existence of inter-intra specific differences in acidity tolerance and NUE in many crops cultivars and genotypes. Genotypes that have high NUE under soil acidity stress may be useful in breeding cultivar with high yield potentials for acid soils. Best Management Practices (BMP) such as crop rotations, improvement of organic matter content in soil, and control of soil erosion, insects, diseases, and weeds can improve crop yields and optimize nutrient use efficiency on degraded infertile acid soils. The development of new cultivars with higher NUE coupled with BMP's will contribute to economically viable and environmentally sustainable crop production systems for the vast acid soil ecosystems of the world.