Evaluation of field layout for the cultivation of other field cropsin bayawa minor irrigation systemin Sri Lanka

Abstract

Minor irrigation systems are very unique to Sri Lankan agriculture for centuries for its role in food security, livelihood and ecosystem sustainability. The objective of this study was to evaluate constraints and potentials of paddy field system layout in a minor irrigation system for other field crop (OFC) cultivation. The study was done in Bayawa minor irrigation system, in Sri Lanka during 2014 and 2015. Data were collected and analyzed to evaluate, system components and their sustainability, canal uniformity, accessibility, and land and farmer plots distribution in the command area. Results according to the system layout reveal that, irrigation canals’ uniformity varies along with the distance from head to tail endswith a water conveyance efficiency of 60%. Canal depth increases mainly due to sand mining, thus,requires a large amount of irrigation water for maintaining a hydraulic head in canals in order to supply irrigation water to fields under gravity. Positive hydraulic head of the right canal up to 70% of its length facilitates water distribution from canal to fields, but negative hydraulic head of the left canal constrains for that. As of the system layout and canal distribution, plot to plot irrigation is the common practice in the command area. The number of plots vary from 2-19 with the highest frequency of 6 plots. Cultivation of OFCrequires individual access to water to each plot. Hence, this irrigation and drainage system restrict OFC cultivation. Furthermore, 56% farmers hold less than 0.4 ha farmer fields due to land fragmentation over the years. This also leads to, low accessibility of individual field plots to irrigation canal and identified as major constraint to OFCcultivation.

Keywords

• drainage, hydraulic head, irrigation, minor tanks, other field crops