Criteria of  harvesting of cane at right time:

Crop Age

Harvesting is done based on maturity (age) group. Farmers who grow a particular variety are usually conversant with the harvesting time. Even most sugar factories give cutting orders to farmers based on crop age. This is not a scientific method since, planting time, crop management practices, weather conditions etc influences maturity.

Visual Symptoms

Yellowing and drying of leaves, metallic sound of mature canes when tapped, appearance of sugar crystal glistening when a mature cane is cut in a slanting way and held against the sun are some of the visual indices of assessing maturity of cane.

Quality Parameters

Important sugarcane quality parameters for assessing cane maturity are the juice Brix, pol or sucrose percentage and purity.

• Juice Brix: Juice Brix refers to the total solids content present in the juice expressed in percentage. Brix includes sugars as well as non-sugars. Brix can be measured in the field itself in the standing cane crop using a Hand Refractometer or  Hand Refractometer Brix or HR Brix. In the field using a pierce collect composite juice samples from several canes. Then place a drop of the composite juice sample in the Hand Refractometer and measure the Brix reading. The circular field gets darkened relative to the Brix level, which could be easily read. The HR Brix meter has graduations from 0 to 32 per cent. The HR Brix readings can be separately taken from both top and bottom. A narrow range indicates ripeness of the cane, while a wide difference indicates that the cane is yet too ripe. While, if the bottom portion of the cane has lower Brix value than the top, it means that the cane is over-ripened and reversion of sugar is taking place.
• Juice Sucrose Or Pol Per Cent: The juice sucrose per cent is the actual cane sugar present in the juice. It is determined by using a polarimeter, hence sucrose per cent is also referred to as pol per cent. For all practical purposes pol % and sucrose % are synonymsNow a days an instrument called sucrolyser is also available for determining sucrose % in juice.
• Purity Coefficient: It refers to the percentage of sucrose present in the total solids content in the juice. A higher purity indicates the presence of higher sucrose content out of the total solids present in juice. The purity percentage along with sucrose percent aids in determining maturity time.
•                 Purity Percentage = (Sucrose %/HR Brix)100
• A cane crop is considered fit for harvesting if it has attained a minimum of 16%  sucrose and 85% purity.
• Reducing Sugars: The reducing sugars refer to the percentage of other sugars    (fructose and glucose) in the juice. A lower reducing sugars value indicates that much of the sugars have been converted into sucrose.
• Commercial Cane Sugar: The commercial cane sugar (CCS) refers to the total recoverable sugar percent in the cane. This could be calculated by the following formula:

CCS (tons/ha) = [Yield (tons/ha) x Sugar Recovery (%)] /100

Sugar Recovery (%) = [S - 0.4 (B - S)] x 0.73

 Where, S= Sucrose % in juice

      and B= Corrected Brix (%)