Progressive growers like Haji Nadeem Shah eagerly adopt innovative ways of farming. Recently, he tried a relatively new method of cultivating wheat, sunflower and cotton on 14 acres.

The technique is called permanent raised beds (PRBs). Facing a shortage of irrigation water as his farm is located at the tail-end region of the canal, he opted for PRB and drip irrigation.

PRB-based cultivation helped Shah in conserving water and getting better productivity of all three crops. He proposes that farmers in Sindh consider this option by looking at its cost and benefits. Growers don’t need to prepare land, which is time-consuming and involves considerable expenses before every crop sowing.

The growth of weeds on raised beds can be tackled by using weedicide. Otherwise, weeds and left over roots of the preceding crop can serve as a source of organic fertiliser. Time is crucial for getting good crop yields, and late sowing compromises per acre productivity.

Permanent raised beds help conserve water consumption by 30-40pc and also improve crop productivity

With PRBs in place, farmers can have timely sowing, as they don’t have to waste any time in preparing the land. Unfortunately, Nadeem Shah had to abandon PRBs after three years, as he could not bear the cost of electricity bills for operating the tube wells.

PRB improves soil management and helps conserve water consumption by 30-40pc. In this technique, 3-4ft wide trapezoidal beds are formed amidst furrows. They are kept intact for a few years to grow multiple numbers of crops. PRBs do not need deep tillage. A particular portion of the raised beds is somewhat loosened prior to the sowing of the seed, with minimal disturbance to roots of the preceding crop.

Resultantly, microorganisms of roots and soil are retained to promote biological activity, and for roots’ health and organic matter. Greater air and water movement are achieved for better productivity and irrigation efficiency. PRBs absorb water released in furrows. On the other hand, in the raised bed (RB) technique, the beds are demolished and then formed every year.

It was around mid-2000 when, according to Sindh agriculture engineering Director-General Agha Zafarullah Durrani, the federal government had launched the PRB project with Australian assistance. Trials were also conducted in Sanghar, Mirpurkhas and Jamshoro districts. It yielded good results for water conservation and crop productivity, says DG Durrani.

A researcher at the Pakistan Council of Research in Water Resources (PCRWR), Ahmed Zeeshan Bhatti, points out that a crop ideally grows if it gets 50pc each of water and air in the root zone. In flood irrigation, particularly in low-lying areas, excessive seepages lead to an imbalance in this ideal air-to-water ratio. “PRBs and RBs are effective ways for keeping this ratio within the ideal range,” he comments.

PRBs, however, have some limitations. The most important is the build-up of excessive salt concentration over time in the beds due to capillary action of water as it evapotranspires, leaving the salts behind. This can be avoided by integrating PRBs with a drip or sprinkler irrigation system, which requires less water but affects intermittent leaching of salts. It has been proven by research trials that PRBs ensure water conservation ranging between 30-40pc, and are preferred over RBs where canal water supplies are normal.

RBs are more suitable for salinity-hit lands than PRBs. These are to be formed afresh for every crop to keep the salts disturbed and scattered. Hence, their concentration in the root zone is blocked. But the formation of RBs is fuel-expensive. In waterlogged and salinity-hit land, raised beds widen the distance between subsoil water and the plant’s roots to minimise salt impacts, Bhatti explains.

“To me, PRB technology suits Sindh, where issues of water scarcity and waterlogging are serious. These are triggered by over-irrigation of lands and force the government to invest millions in the drainage system’s maintenance to keep the groundwater under control. But PRBs’ success is subject to integration with high efficiency irrigation system,” he says.

Another soil management practice to make PRBs more suitable is the sowing of plants on the edges of the beds, sparing the middle-bed surface where the salts accumulate, he says.

But growers are reluctant to opt for PRBs. Either they are not exposed to it, or are afraid of the initial capital cost of the required machinery and implements. The government may consider giving subsidy on such equipments to promote PRBs, as it is subsidising tractors for farmers. According to DG Durrani, the machinery’s cost for PRBs is not that huge.

Published in Dawn, Economic & Business, Aug 11th, 2014