did you know Plant responses to phosphate fertilization. Factors that affect them.


Pedro Raúl Solórzano Peraza


There is a lot of information about the response of various crops to the application of phosphate fertilizers. In general, there is broad agreement that crop response to P applications and high yields can be expected when:

1.-The soil does not contain high levels of usable or available P for plants.

2.-The other essential nutrients are present in the system in sufficient quantities and are not able to limit yields.

3.-The prevailing climate does not limit the yields of the selected species, to the point that it cannot prevent the eventual response of the plants to P applications.

In the same vein, and considering the importance of the soil-plant-climate system, it can be asserted that crops in soils with low levels of usable P must respond to phosphate fertilization. However, there are other factors besides available soil P content that will affect the magnitude of this response and must be considered in predicting the outcome of phosphorus application. These factors, as already noted, include other soil characteristics, plant species, climate, interactions of P with other nutrients present, and fertilization and crop management practices.

Edaphic factors: among the soil factors that affect the use of phosphorus by plants, the following stand out:

a.-Texture: the adsorption of phosphate anions increases as the clay content of a soil increases as there will be a greater effective surface for this adsorption to occur. This implies that in soils with a high clay content high doses of phosphate fertilizers are required to increase the level of usable P in the soil solution to values ​​suitable for crops.

b.-Aeration: the process of P uptake by plant roots is metabolic and therefore requires energy from respiration; that is to say, there must be an adequate supply of oxygen in the root zone of the crops so that the absorption of P and other essential nutrients is not limited.

c.- Soil moisture: in general, as the usable water in the soil decreases, the absorption of P by the plants decreases, because among other effects, the rate of diffusion decreases.

d.-Content of organic matter: the level of organic P in the soil is highly variable. Increases in the content of organic matter in the soil can contribute to improving the supply of P to plants, either because mineralization takes place or because the organic matter forms complexes with Fe and Al ions, reducing the capacity to fix phosphates in acid soils.

e.-pH: it is considered that the best pH conditions for the utilization of phosphates by plants take place, in general, at values ​​between 5.5 and 7.0.

The floor: different plant species vary in their phosphorus requirements, as well as their ability to use the various forms of soil P. As examples we can cite that the granifer snail with a yield of 3,000 kg of grains/ha accumulates about 25 kg of P2O5/ha, while soybeans, for a yield of 3,400 kg of grains/ha accumulate about 80 kg of P2O5/ha. This, logically, influences the amount of phosphate fertilizer that needs to be applied to one or another crop.

The climate: as generally pointed out, for the conditions of Venezuela and for most of the tropical areas of the world, the main effect of the climate on the development of the plants refers to the amount of rain that falls per season and its distribution throughout the year, which affects the water-air relations of the soils and consequently affects the use of P by the plants and some agricultural practices such as cultivation, sowing method, weed control, etc.

Handling: the factors of soil, plant and climate presented briefly previously will be determinants of the management of phosphate fertilization, particularly with regard to doses and form of application of the fertilizer. The characteristics of the soil condition the behavior of the native phosphates and those of the applied fertilizer; the requirements and some growth habits of the plants will determine the doses and the form of application of the nutrient; and the climate notoriously influences the best agronomic practices to apply to the system.


Pedro Raúl Solórzano Peraza is an outstanding collaborator of Món Agropecuari

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