Crop nutrition

Crops require a balanced diet of essential nutrients throughout their growth cycle. Yield and the quality of products from crops are strongly linked to the supply of nutrients.

Many plant foods can be found in the soil, but often in insufficient quantities to sustain high crop yields. Soil and climatic conditions can also limit a plant’s uptake of nutrients at key growth stages.

Major nutrients

• Nitrogen (N) is often required in the greatest quantity by crops, primarily for vigor and yield. Nitrogen plays a key role in chlorophyll production and protein synthesis. Chlorophyll is the green plant pigment responsible for photosynthesis. When nitrogen is deficient, plants develop yellow or pale leaves and their growth is stunted.
• Phosphorus (P), is a vital component of adenosine triphosphate (ATP) which supplies the energy for many processes in the plant. Phosphorus rarely produces spectacular growth responses, but is fundamental to the successful development of all crops. For example, maize or other corn crops that lack phosphorus during the growing season achieve lower yields.
• Potassium (K) is needed by virtually all crops and often in higher rates than nitrogen. Potassium regulates the plant’s water content and expansion. It is key to achieving good yield and quality in cotton and critical for increasing the size, juice content and sweetness of fruit.

Secondary nutrients

• Calcium (Ca) is perhaps the most important. Calcium strengthens cell walls, helping to reduce bruising and disease in fruit, salad and vegetable crops.
• Magnesium (Mg) is also important for crop quality, but is also a key component of leaf chlorophyll and the enzymes that support plant growth. Low magnesium leads to reduced photosynthesis, which severely limits crop yields.
• Sulfur (S) is an essential part of many amino acids and proteins. Without both S and Mg, crops suffer; growth slows and leaves turn pale or yellow. Sulfur is particularly important for ensuring the protein content of cereal crop grains.


• Iron deficiencies are common – for example in seed fruits – where the effect is to reduce production of chlorophyll. As a result, crops struggle and younger leaves develop a severe yellowing or chlorosis.
• Boron (B) is needed for the development of shoots and roots, and is essential during the flowering and fruiting phases of crops.
• Zinc (Zn) is needed for the production of important plant hormones, like auxin. Zinc deficiency leads to structural defects in leaves and other plant organs.
• Molybdenum (Mo) is involved in plant enzyme systems that control nitrogen metabolism.
Soil testing is a critical component in determining those nutrients that are already available and those that may be in limited supply. Deficiencies will impact crop quality or yield and knowing these will assist in determining the amount and type of fertilizer required. Soil testing, however, is highly dependent on appropriate soil sampling on an individual field basis.

For this government has launched Soil Health Card Scheme. Under the scheme, the government plans to issue soil cards to farmers which will carry crop-wise recommendations of nutrients and fertilisers required for the individual farms to help farmers to improve productivity through judicious use of inputs. All soil samples are to be tested in various soil testing labs across the country. Thereafter the experts will analyse the strength and weaknesses (micro-nutrients deficiency) of the soil and suggest measures to deal with it.

Practice question:

1) The Soil Health Card Scheme provides the status of soil with respect to which of the following parameters?
1. Manganese
2. pH
3. Organic carbon
4. Electrical Conductivity


a) Only 1

b) 1 and 3

c) 1, 2 and 3

d) All

Ans: d
Exp: It will contain the status of soil with respect to 12 parameters, namely N,P,K (Macro-nutrients) ; S (Secondary- nutrient) ; Zn, Fe, Cu, Mn, Bo (Micro - nutrients) ; and pH, Electrical Conductivity, Organic Carbon (Physical parameters).