calculate the requirement of SOP for 2 hector area of potato crop (80:60:60)
Answers
Importance of potash for potatoes
Potash (potassium, K) is an essential nutrient for all plants and has a major effect upon yield and quality of potatoes as well as the general health and vigour of the crop. It is involved in regulating the amount of water in the plant; in the absence of sufficient potassium crops do not use water efficiently. Also adequate K levels in the plant help it to withstand water stress during periods of drought. Potassium plays a vital role in maintaining the turgidity (rigidity) of plant cells. Because of its importance in turgor maintenance, potassium is essential to obtain maximum leaf extension and stem elongation. This helps to achieve rapid ground cover so maximising interception of sunlight and thus the rate of growth in the critical early periods of the growing season which is of particular importance for spring sown crops such as potatoes. Another need to ensure an adequate supply of K is because it plays a vital role in the movement of sugars, produced in the leaf by photosynthesis, to the tubers where the sugars are converted to starch. Potassium also contributes to various aspects of tuber quality that may be vital for a marketable sample. The balance between nitrogen (N) and K supply is of particular importance for this crop.
There is little doubt that crops deficient in potash are less able to handle stress caused by drought, waterlogging, frost, heat, wind, etc. However, it appears that there is no advantage to gained from applying larger amounts of K than those justified for yield or replacement requirements. Whilst yield variation will occur according to the growing conditions in different years, smaller yields in “poor” years can be minimised by ensuring an adequate potash supply.
Potash shortage leads to:
Low yield
Poorer marketable quality
Thinner cell walls and less lignification
Weaker stems
Reduced resistance to disease
Lower starch content of the tubers
Increased susceptibility to bruising and mechanical damage
Greater susceptibility to the adverse effects of drought
Lack of response to nitrogen
Deficiency
Symptoms of deficiencyYield loss and adverse effects on quality may occur without any visible symptoms of K deficiency being seen in the leaves. When symptoms are identified, potential yield loss is likely to have already occurred and it is unlikely that this can be recovered by adding K. The visual signs of potassium deficiency are that the leaf margins, especially on the older leaves, become brown and leaves die prematurely. In severe cases, growth is much retarded and the leaf canopy may not close between the rows. Growth may be very uneven across the field and this can have serious consequences for the yield and quality of the crop.
Forms of potash
Potassium occurs in nature as various salts that occur in very large, mainly underground, deposits. These deposits can be mined and the salts purified to supply the potash fertilisers used commercially. These K fertilisers are soluble in water and when dissolved they separate into the two components, the cation K+ and the anion Cl–, SO42-, or NO3–, according to the form of the fertiliser applied.