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.
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.
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.
Animal levelling board
2-wheel tractor harrows
4-wheel tractor blade
Total costs ($/ha)
In summary, the main benefits of levelling are:
- improved crop establishment,
- even water coverage of the field,
- even crop stand and maturation,
- reduction of weeds by up to 40 % (thereby a 75 % decrease of labour required for weeding),
- increase of farming area by 5-7 %,
- reduction of farm operation times by 10-15 %,
- within rice production, the possibility of changing from planting and transplanting to direct seeding which results in reduced labour of 30 person-days per ha, and
- average yield increase of 10- 20 %
Costs and net profit – Example from Egypt
In Egypt, the Egyptian-German Water Resource Management Reform Programme quantified the costs and benefits (in Egyptian Pound (LE) per feddan and year) of land levelling. As most farmers in Egypt do land levelling, the data did not compare plots where no levelling had been conducted. Highest yield increase and cost savings were achieved by using a laser unit. Moreover, land levelling by laser method is done only every 4th year, whilst the other methods require annual levelling.
The highest net profit can be obtained with precision laser levelling, but it is not commonly used. This can be due to a variety of factors: limited access to laser units (the few units available cannot be used all year round, but only during a limited period before planting rice or wheat); infrastructural problems (too narrow roads, too high water tables for the heavy machinery); or gender constraints. Other important issues are the relatively high costs compared to regular levelling (although they arise only once in four years) and the increase of costs per unit when used on small, individual plots of less than one feddan.
FAO (1989): Guidelines for designing and evaluating surface irrigation systems.
GIZ/ Weber (2005): Guidebook for Extension Training in Agricultural Water Management, Module No.4. Cairo.
GIZ (2010): Training Manual for Agricultural Water Management Specialists: Executive Summary, Cairo