Sustaining Crop Production in the Developing World through “The Nutrient Buffer Power Concept”.
K.P.Prabhakaran Nair, Government of Kerala, Agricultural Reforms Committee, Opposite Rotary Center, P.O. Ajanur, Kanhangad, 671 541, India
Human impact on soil quality attributes determine the scope and direction of future food production in the world, especially in the developing world, where the so-called “green revolution” has been showing dramatic fatigue in may regions of Asia. Yields of principal cereals like wheat and rice are plateauing and response to applied fertilizers is on the decline. A number of soil-related problems resulting in decreased fertility are surfacing. Nearly after two decades when the so-called green revolution has run out of steam, it becomes imperative that a careful examination is made where we stand inasmuch as food production is concerned, especially against the background of providing adequate nutrition to crop plants, which creates the greatest human impact on crop production vis-a-vis soil quality. Sustaining crop production in the developing world is crucial to its food security and of all the factors of production, the nutrient factor is the most crucial, and, yet, the least resilient to management. This paper summarizes research results of the author in Europe, Africa and Asia, spanning a period of more than two decades on a revolutionary soil management technique to sustain crop productivity. It is now known, the world over, as “The Nutrient Buffer Power Concept”. The technique precisely quantifies a soil nutrient's “Buffer Power” which is then integrated into the computations to devise accurate fertilizer recommendations. The concept centers on the dynamics of soil nutrient bio availability and is essentially rooted in Fick's first law, F = -D(dC/dx) where F = the flux, dC/dx = concentration gradient across a particular section, and D = the diffusion coefficient for which Nye (1979) gave an operational definition as D = D10f1 (dC1/dC) + DE where D1 = diffusion coefficient of the solute in free solution, 0 = the fraction of the soil volume occupied by solution and gives the cross section for diffusion, f1 = an impedance factor, C1 = concentration of solute in the soil solution, DE = an excess term which is zero when the ions or molecules on the solid have no surface mobility, but represents their extra contribution to the diffusion coefficient when they are mobile. DE can generally be neglected since only in rare instances will it play any role in diffusion of plant nutrient ions in soil (Mengel, 1985). When we consider plant nutrient bio availability dC1/dC representing the concentration gradient , where C1 = concentration of the nutrient in the soil solution and C = concentration of the same ion species in the entire soil mass assumes considerable significance in lending a practical meaning to nutrient bio availability. When the term “capacity” or “quantity” is ascribed to C and “intensity” to C1, we have in the above term an integral relationship between two parameters that may crucially affect nutrient bio availability. Since the concentration gradient of the depletion profile of the nutrient in the zone of nutrient uptake depends on the concentration of the ion species in the entire soil mass (represented by “capacity or “quantity”) in relation to the rate at which this is lowered on the plant root surface by uptake (represented by “intensity”), Nair (1984) argued that a quantitative relationship between the two should represent the rate at which nutrient depletion and/or replenishment in the rooting zone should occur. This relationship which was functionally quantified by Nair and Mengel (1984) was designated as “Nutrient Buffer Power” and Nair (1996, 2002) has made an extensive review of the experimental results he obtained with regard to the importance of the “Buffer Power Concept” in precisely explaining soil nutrient bio availability in the case of several test crops, such as, maize, rye, white clover, turmeric (spice crop), among annuals, and black pepper and cardamom among perennials in a wide variety of soils across Europe, Africa and Asia. The technique was field tested wherein, by integrating the “Nutrient Buffer Power” precise fertilizer recommendations could be devised. A number of success stories were achieved, as for example, wherein in Central Asia Zn fertilizer recommendation to the wheat crop could be reduced by as much as 75 per cent. So also in the case of the perennial Cardamom crop (Elettaria cardamomum M.), world's second most important spice crop in the State of Kerala, in India, Potassium fertilizer application was found to be far more closely related to the Potassium “Buffer Power” than the classically estimated NH4OAc extractable K. The coefficient of determination for P estimation in the case of Rye (Secale cereale L.) in Central Europe improved by as much as 80 per cent. In the case of Black pepper (Piper nigrum L.), the economically most valuable spice crop of the world, Zn fertilizer application was found to be very precise based on the Zn “Buffer Power” rather than the routinely used DTPA extractable Zn. The International Fertilizer Industry Association in Paris selected this project for the “First Runner Up” position, from among 25 nominations around the world,for the very prestigious International Fertilizer Award, 1999. Very recently the National Science Movement of the Government of India selected the author for the prestigious “Science Award 2005” for developing the concept.