Back S. Ahmed, M. Aslam, Jehan Zeb1, T. Hussain and H. Zia2
Water Resources Research Institute, NARC. Islamabad, Pakistan1 and
Department of Soil Science, University of Agriculture, Faisalabad, Pakistan2
Full Paper (PDF File: 368KB)
Abstract
The groundwater in the Indus basin contributes around 35 percent of the total water available for agriculture on 17 million hectares. Water quality of 60 percent area of the basin is marginal to brackish in quality. The use of sodic or saline-sodic groundwater contributed to secondary sodification. Therefore, farmers have to use gypsum as an amendment, which has very low solubility, and thus its use is not cost effective without public sector subsidy. The Sulfurous Generator technology requires high initial investment of around US$ 25,000 with higher operational cost. The research studies were conducted to design and build a EM Bio-generator with initial investment of US$300-400 for a farm size of 10 hectares. The propagability of EM is extremely high and EM 1 can be extended in three phases using ratio of 1:1:20 (EM:Molasses:Water). Therefore, one litre of EM 1 can be extended in three phases to 22, 484 and 10648 litres of extended-EM, super-extended EM and supra-extended EM, respectively. A pH of 4.0 can be achieved after 3-4 days of detention. After the first cycle, the whole process can be completed in 3 days in summer and 7-8 days in winter season. The supra-extended EM was used to amend sodic groundwater using a ratio of 1:100 (EM:Water) which reduced one unit of pH i.e. from 9.5 to 8.5 and reaction was stable for 44 days with further reduction in pH. The amended water will further help to manage the sodic soil. In fact, the acid forming character of EM is very encouraging because improvements in soil productivity would be an added benefit in addition to amending sodic water. The techno-economic analysis indicated that once the microbial mass is built in the soil, much less EM will be required to amend the sodic water. Comparative studies of EM with other traditional amendments like gypsum and sulfuric acid were conducted. The initial results indicated that low solubility of gypsum is a major limitation in having chemical reaction in soil because of heavy depths of water required for leaching. The waterlogging problem, scarce water resources and high pumping cost do not permit farmers to use additional amounts of freshwater for leaching. Apparently, the EM amended water would not require extra leaching because monsoon rains can provide leaching. Furthermore, gypsum also add salts in soils which are already high in salinity, whereas total solids of EM are all organic based and thus would not add much towards salinity of soil. Lysimeter studies reveal that by lowering down one unit of pH of sodic water through addition of Supra-extended EM, there was 70.54 percent decrease in soil SAR build up as compared to control (29.9 percent). The potential of EM Bio-generator is immense especially for semi-arid and arid environments where calcareous soils having pH of 8.0 or more are very common. The acidic nature of EM would be a blessing for future agriculture using marginal groundwater and still soil quality can be managed on sustainable basis. Although, there is a resistance from traditional scientists in accepting the technology farmers have already started using it at their own cost in an environment where almost every intervention including chemical fertilizers were introduced with a subsidy from the government. This is the encouraging aspect of the Bio-generator in Pakistan. Future research would be directed towards integrated systems including biogas and amending saline groundwater.