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Importance of Secondary Nutrients

Importance of Secondary Nutrients: Calcium

  • Calcium plays an important role in lengthening the roots and shoots and there by improving the growth and development in plants

  • Calcium requirement of groundnut plant is quite high and it is more during the pod-filling stage.

  • 90% of calcium uptake is during flowering and pod formation stages.  

  • An important aspect of calcium nutrition in groundnut is that the calcium taken up by the plant from soil will remain in the leaf tissues, and will not move from the leaves to the developing pods where its requirement is high.

  • For this reason calcium should be sufficiently available in the podding zone at peg formation stage to pod maturity.

  • Developing pegs and pods can directly absorb soil calcium similar to absorption by roots.    

  • To get good yields of quality groundnut pods, adequate amount of calcium should be present in the soil from early flowering of the crop onwards.  

  • Gypsum which is calcium sulfate is the cheapest source of calcium.  

  • Gypsum is a byproduct from fertilizer factories. Gypsum is relatively soluble and hence a readily available source of calcium for the developing pods.  

  • Depending on the soil test, application of 250-500 kg/ha of gypsum is recommended.  

  • Well - powdered gypsum should be applied when the crop is in peak flowering stage i.e. 40 days after sowing.   

  • Gypsum is applied by placing it all around the plants followed by manual weeding which also helps to incorporate the applied gypsum.  

  • As there is little residual effect of gypsum in the soil, it is necessary to repeat gypsum application every season.

Magnesium Nutrition  

  • For growth and development plants require energy rich compounds.

  • These energy rich compounds are produced in plants from sun’s energy through a process called photosynthesis.  

  • Chlorophyll, a green pigment in leaves, is the place where photosynthesis takes place.

  • Crop plants cannot produce yield without chlorophyll in their leaves

  • Magnesium is a part of chlorophyll and thus is important in providing energy rich compounds for growth and development of plants.

  • Magnesium helps groundnut crop in utilizing other plant nutrients, like phosphorus, efficiently.

  • Magnesium is mostly deficient in problem soils with low, as well as very high pH i.e. in acid soils or alkali soils.

  • Testing the soil will indicate the need to apply magnesium or not for groundnut crop.

  • Magnesium is applied broadcast before final ploughing as elemental magnesium at 10 kg/ha, or as dolomite which is a mixture of calcium and magnesium carbonates (14 to 20% calcium and 8 to 10% magnesium).

  • If magnesium deficiency is found in the early stages of a standing crop, 1% magnesium sulfate can be sprayed on the foliage to correct the deficiency.

Sulfur Nutrition


  • Sulfur also is an essential element for plant growth and plays a role in the formation of chlorophyll and protein synthesis.

  • Sulfur is also involved in many processes that are required for proper growth of plants.    

  • Crops take up about 10 to 20 kg of sulfur for normal growth.

  • Sulfur is important in improving the oil content in groundnut.

  • The importance of sulphur in improving yields of groundnut was not noticed in the past as the sulfur requirement of the crop was met indirectly.

  • Use of ordinary super phosphate as a phosphorus source (10 to 12% S), gypsum (CaSO4) as a calcium source (18 to 23% S), and dusting with elemental sulfur for leaf spot control (as much as 120 kg S per ha) are all practices which provided sulfur to groundnut crop.

  • The substitution of lime for gypsum as a calcium source, use of high analysis fertilizers like Diammonium Phosphate (instead of super phosphate), urea against ammonium sulfate etc., and decreased use of foliar-applied sulfur for leaf spot control, have lead to reduced sulfur availability to groundnut crop.

  • The above recent changes in groundnut cultivation could lead to sulfur deficiencies in the future, and the situation needs watching.

  • The need for sulfur application to groundnut crop should be assessed through soil testing.

  • Sulfur need to be applied to groundnut crop if soil test indicates less than 10 ppm of available sulphur.

  • Gypsum is a good source for sulfur (18 to 23% S) application.

  • Soil application of 250 kg/ha of gypsum help in increasing the pod yield in groundnut

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