Influence of lime and farm yard manure
par Dieudonne MUGOBOKA
ISAE Busogo - Bachelor's Degree 2008
Phosphorus is one of major essential plant nutrients .It is essential for plant growth, cell division ,root growth and lengthening seed and fruit development and early ripening .It is absorbed as H2PO4-- and HPO4-- forms.
According to Miller (1990), it is the one key plant nutrients .It is an essential part of nucleoproteins in the cell nuclei, which control cell division, and deoxyribonucleic acid (DNA) molecules, which carry inheritance characteristics of living organism. In its many compounds, phosphorus has roles in hastening plant maturity, energy transformation within the cell, and in fruiting and seed production.
According to Russell (1995), root crops suffering from severe phosphorus shortage are also stunted and the effect of added phosphorus can be spectacular .As matter of history, the early workers were so impressed with the great increase in the yield of roots obtained by phosphate fertilizers, which they assumed the phosphate had a specific action in encouraging root development.
Under the P deficiency, the plant has restricted growth of both tops and roots characteristics with thin, erect and spindly stems, restricted foliage consisting of narrow leaves, suppressing lateral buds. The leaves turn into bluish color.
Older leaves become bronzed, reddish, brown or purple in color having dead tissues all the tips. The symptom first appears on the tips or on the margins.
In case of cereals and millets, the plants have bluish -green
leaves, reddish-purple tints at the internodes, leaves or even heads, while
Potatoes tubers develop rusty lesions. The ear heads are poorly formed,
maturity is delayed and lack of poor seed and fruit development is observed
Chemical elements (Iron and Aluminum), both from compounds of low solubility with po4 ions in acid soils .From pH 5.0 up to neutral point, soil phosphates have an appreciable solubility on account of basic ions present that maintain the high pH and at the same time form some Ca and Mg phosphates in soil .In soil from about pH 5.0 down ward, however, complex phosphates of ion and Aluminum may be formed, which have a very low solubility and do not supply sufficient phosphorus to plants. The Ca and Mg phosphates are more soluble in the presence of CO2, which comes from decaying organic matter, but this solubility effect decreases up to about pH (Millar, 2004)
According to Mohsin (1995), there are three important problems that are generally associated with the management for crops sequences:
Ø Small amount of phosphorus in soil
Ø Low availability of native phosphorus soil
Ø High fixation of added phosphorus in soil
Behavior of P in acid soils depends to some extent the concentration of soluble and active Aluminum and Iron besides P carriers used. Soil characteristics like soil reaction, sesquioxides content etc...influence the response of crops to added fertilizers in acid soils. Addition of phosphate fertilizers to soil may not solve the problem as 71 to 80% of it remains in soil and only 10to15 %reaches the plant.