Harvest index and crop yield

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Harvest index and crop yield

The crops which provide edible seeds are considered under the category of cereals. The grains of the cereals like rice, wheat, maize, lentil etc are the rich source of carbohydrates as well as proteins for human beings. The improvement in the yield of a crop depends upon various endogenous or exogenous factors. These factors vary from crop to crop. Harvest index is the basic factor which affects the production of a crop.

There are some factors which contribute in the production of every crop,:

  •  Net assimilation rate(NAR)
  • Leaf area index(LAI)
  • Leaf area duration(LAD)
  • Crop growth duration
  • Crop growth rate(CGR) etc.

What is Harvest index:

  • It is generally known as the measurement of crop yield.
  • It is the ratio of the total grain yield of a crop versus its biomass. Mostly the above ground biomass is preferred as compared to below ground biomass because it is very difficult to calculate the biomass of roots etc.
  • It is the basic trait for plant breeding because it deals with the “how much biomass allocate by the plants in the formation of its reproductive parts”.
  • Harvest index is considered as a yardstick to measure the gap between the potential yield and actual yield.
  • Harvest index is the ratio of total grain yield and total plant yield. (The total plant yield may be considered as the above ground vegetative parts of plants).
  • It is used as a efficiency indicator.
  • It is influenced by genetic traits as well as environmental factors.

Harvest index for different crops:

The grain yield per hectare of various crops far below the international standards. The modern cultivars having harvest index with in the range of 0.4- 0.6. But mostly different crops have different harvest index. For example:

  • Wheat(gandum)                      0.4-0.5
  • Maize(makai)                           0.4-0.5
  • Sunflower(surajmukhi )        0.3-0.4
  • Beans                                         0.45-0.55
  • lentils(masoor)                        0.45-0.55
  • sorghum (charri)                     0.4-0.6
  • soybean 0.25-0.35

The reasons for a low harvest index of a crop are :

There are some major factors which causes the low harvest index of a crop which ultimately lead to the low yield.

  • Use that variety which is not recommended for that area
  • Use the inappropriate seed rate
  • Use of unapproved seed for sowing
  • Late sowing of seed of a crop
  • Use imperfect method of sowing
  • Lower Plant population
  • Attack of different type of diseases
  • Attack of insects pest
  • Lower plant protection
  • Weeds problem
  • Fertilizer application may not be applied according to crop need
  • Less irrigation

How the H.I of a crop can be increased?

There are several factors which may help in the increase of the harvest index of a crop and ultimately leading to its highest yield.  The possible approaches to increase the H.I of the crop are:

  • Increasing post anthesis biomass production
  • Increased partitioning of biomass to sink by improving sink characters .
  • Extent the post anthesis biomass production.
  • Proper fertilizer application (eg. In sunflower, 2% boron applied in soil helps in the 29% increase in the harvest index and ultimately 53% increase in the yield).

Conclusion:

Harvest index contain genetic variability, thus it can be used as a selection criterion for the productivity of a crop.

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