## Tuber yield estimation

A basic formula for production is:

Foliage and production

A judgment of the foliage in terms of: crop density (stem density), light interception, the quality of the foliage as well as on a balanced plant growth is necessary to estimate yield.

A balanced crop shows sufficient, but not abundant, haulm growth.

Production per day - bulking

It is estimated that, once the full bulking has started, the daily increase in tuber yield (the bulking rate) is close to __700 kg per hectare per day or 20 grammes per plant per day.__

Thus each day that the foliage remains healthy green, is turgid and intercepts 100% of the incoming light, the yield increases with 700 kg per hectare. With long days and high light intensity in optimal conditions a producton of __1000 kg per hectare/hectare/day__ may be reached.

Balanced plant growth

A balanced plant growth is needed to obtain optimum tuber growth. Haulm growth can neither be too abundant nor be too limited, but has to be adjusted to optimal production in the period available for production.

Growth pattern

Calculations on potential yield

Potential yields can be calculated based on light interception. Such calculations allow comparisons between potential yield with actual yield.

The gap between both the actual- and the potential yield is an indication for improvements to be made.

CALCULATION OF POTENTIAL YIELD

Tuber yield estimation

Potential yield of a potato crop is estimated by judging a number of crop characteristics at a certain stage of the crop:
- plant density
- stem density
- percentage soil cover (ridge size and ridge shape)
- colour of leaves (nutrition)
- ratio: haulm growth/tuber growth
- growth stage of the crop in relation to the period still suitable for growth
- presence of diseases and pests
- availability of water