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Estimating Field Losses of Rice in Asia, Using Small Quadrat Samples

IRRI, P.O. Box 933, 1099 Manila, Philippines

^* Corresponding author (m.bell{at}cgnet.com).

Field losses of rice (Oryza sativa L.) in small fields of Asia are rarely quantified. In developed countries, loss is often measured using devices attached to large combines. Such harvesting equipment is rarely used in Asia, so quadrat counts are more applicable. We estimated field losses of rice using a 10- by 10-cm rigid quadrat in commercial fields on Luzon in the Philippines. Losses ranged from 66 to 503 kg ha^–1. Due to the rapidity of the quadrat counts, sample variability throughout the field was easily assessed. By counting the number of seeds and multiplying by 22 to 25 (typical range for 1000-kerneI weight), field loss (kg ha^–1) was estimated directly. To estimate field losses within ±50 kg ha^–1, a rule of thumb of three is suggested (i.e., the total number of samples required is approximately three tunes the average number of grains being counted in the sample). A sequential sampling procedure is presented for efficiently determining whether grain losses are below a specified tolerance. The quadrat method is an option for rapid assessment of losses, especially by farmers, where more sophisticated methods are not available.

Received for publication July 21, 1995.