Revision as of 07:37, 17 August 2012 by
***** (***** | *****) Land Levelling
Land levelling is a measure used in surface irrigation, such as basin and furrow irrigation. It consists of:
- preparing the irrigation plot in a way that no high and/or low spots disturb the uniform distribution of irrigation water on the field, and
- ensuring the optimal slope for water movement across a field when irrigated.
Levelling results in more efficient irrigation and, if fertigation and chemigation are applied, in more efficient use of fertilizers and pesticides. In an unlevelled field, high spots might not be covered by irrigation water, and the dissolved nutrients and/or pesticides might percolate unused into the soil. In case of low spots, water and the dissolved nutrients and chemicals might accumulate there and create zones of water logging and nutrient or pesticide accumulation. This in turn will disturb soil aeration and water uptake by crops. In either case, the uniformity of the crop cover is disturbed and yields might decrease.
1. Technical parameters
Levelling can be done manually or with machinery and corresponding equipment. Heavy earth movement should be avoided in order to keep the natural soil structure undisturbed, thus maintaining good growing conditions for the crop roots and keeping costs low.
Experienced farmers often do land levelling according to visual assessment, e.g. on small plots with hoes, or with draft animals and equipment such as ploughs and bars or scrapers. Equipment such as grading blades and hydraulically operated levellers mounted on wheels are used with tractors.
More advanced and sophisticated levelling equipment is operated with a laser emitter, a laser sensor or receiver, and a scraper pulled by a tractor. After the desired level or slope of the field and/or the difference of the high and low spots have been surveyed, the emitter is set to send a rotating laser beam creating a plane of laser light above the field surface. The laser light is used as the levelling reference. It directs the hydraulic system of the moving tractor and scraper, and thereby controls the levelling.
2. Effects and benefits of land levelling
The International Rice Research Institute (IRRI) provides the following data regarding the costs for land levelling during rice cultivation in Cambodia from 1996 - 1999. As shown in the table below, the total cost of levelling depends on the technology used.
