Factors causing low head rice recovery in combine-harvested paddy

For paddy harvesting, old conventional wheat combine harvesters induce impact threshing forces on kernels, which result in a higher rice breakage during milling. This study was designed to identify the causes of low head rice recovery in combine-harvested Super Basmati rice grown in the Punjab province of Pakistan. Data were collected from 32 fields evaluating four types of conventional and four types of head-feeding combine harvesters. The quality of milled rice of combine-harvested paddy was compared with manually-harvested paddy. The manual harvesting and threshing gave the highest head rice recovery (64.24%) followed by head-feeding combine harvesters (62.38%). Conventional combine harvesters gave the lowest head rice recovery (58.23%). Manual harvesting method gave more shattering losses (up to 13%) due to many crop handling operations. Conventional combine harvesters gave 12% shattering losses and 7% threshing losses. Similarly, head-feeding combine harvesters gave 3.5% shattering losses and 1.5% threshing losses. Crop health was identified as an important factor yielding low head rice recovery. Healthy crop gave better head rice recovery than the medium or weak crop. Other factors yielding low head rice recovery included crop status (standing or lodged), crop moisture, machine parameters (forward speed and cylinder speed) and operator's skill. Operator's skill was perhaps the most critical factor to control rice breakage during combine harvesting of paddy crop. Head-feeding combine harvesters produced lesser broken rice than the old European wheat combine harvesters and are therefore more viable option for paddy harvesting. (author)