Chapter Three - Differences of Some Leguminous and Nonleguminous Crops in Utilization of Soil Phosphorus and Responses to Phosphate Fertilizers

Abstract

As a vital component of a number of macromolecules and an integral part of energy metabolism and major biological processes in photosynthesis, respiration, and membrane transportation, as well as playing a genetic role through ribonucleic acid and energy transfers via adenosine triphosphate, phosphorous is indispensable for all life forms and cannot be substituted by any other element. Being the life-limiting element in natural ecosystems, regular inputs of P fertilizer to replenish the P removed from the soil by crops are one of the characteristics of modern agriculture. The demand for P resources will outstrip supply in the coming decades because the global commercial phosphate reserves may be depleted in another 60–130 years. In addition, rock phosphate (RP) reserves are under the control of a few countries. The P recovery rate is very low and the surpluses of P in soil have produced variable responses of crops to P fertilizers and environmental pollution. Requirements for direct application of RP and improvement of P fertilizer efficiency have led to adoption of specific plant species. Since leguminous crops in general respond better to P fertilizer than cereals, some scientists have proposed the application of P to leguminous crops as the first priority. Many hypotheses have been proposed to explain the different responses to P fertilizer between the two types of crops, but most of them have not been substantiated. A series of experiments have been conducted by us on different aspects for more than 40 years, and this chapter reviews the current investigation status and reports our viewpoints based on results obtained mainly from wheat [Triticum aestivum (L.) em. Thell], pea (Pisum sativum L.), maize (Zea mays L.), and soybean [Glycine max (L.) Merr.] One reason for the different response to P fertilizer supposes that legumes require more P than nonlegumes. A long-term experiment in a maize–maize–soybean rotation sequence in which maize and soybean were grown in the same season with almost the same duration of growing period showed that the total P uptake by soybean from unit area was similar to that of maize and in some cases uptake by maize was higher than that by soybean. Results of pot and field experiments conducted by us showed that P uptake amount by leguminous crops was not higher than that by cereal crops, and wheat had a higher capacity to use soil P than do pea and vetch. Without application of N fertilizer, P amounts taken up by legumes were equal to or slightly higher than those of nonlegumes, while cereal crops with N application took up much more P than legumes in most cases either with or without application of P fertilizer....