The extent of water logging and salinity is more pronounced in Sindh than elsewhere in Pakistan

By Dr. S. M. Alam and
Dr. R. Ansari Nuclear Institute of
Agriculture,Tando Jam, Pakistan
Jun 19 - 25, 2000

The total land area of Sindh, which lies between 23 and 29 degrees north latitude and 67 and 71 degrees east longitude is 14.1 million hectares (or 34.84 million acres), represents 18% of total geographical area of Pakistan which is 79.61 mha. Out of this nearly 39 per cent or 5.45 million hectares (or 13.45 million acres) are cultivable. About 9.9 per cent is culturable wastes and 0.57 mha or 4.8 per cent is under forestry. The remaining 8.65 mha or 44.2 per cent is not available for cultivation. Again of the total cultivated areas of 5.45 million hectares, nearly 57 per cent are current fallow, which is the highest in the country and reflects on the poor water availability, mismanagement and ill-practices of irrigation systems in the province. It is stated that out of the salt free, i.e. cultivated or cropped areas, which are 3.079 million hectares or 57%, about 2.321 million hectares (or 42%) are salt-affected . This includes 1.342 million hectares (or 57 %) of highly saline., 0.673 million hectares (or 2.9%) of permeable saline-sodic. Similarly, 0.277 million hectares (or 12%) of impermeable saline-sodic and 0,028 million hectares (or 1.2%) of sodic soils. The menace of salinity is towards increasing end. The experts have estimated that the fertile lands of Pakistan are becoming saline at the rate of 40,000 hectares annually. This shows that 109 hectares of our land is converting into saline daily. This situation is very alarming and particularly in Sindh province, because lands are becoming saline more in Sindh than the other provinces. The climate of Sindh is arid and hot. On an average, the region receives the maximum rainfall of 170-200 mm. During summer the temperature goes to 53C . The coldest season is from December to February. July to mid September is the monsoon season.

In Sindh, the salt free areas (Electrical Conductivity (ECe) of less than 4 dS/m, where salts are not visible at the surface) in this case, all kind of crops can be grown without any difficulty. The soils which are slightly saline have EC between 4-8 dS/m, where salts are slightly visible at the surface, and under such conditions growth are uneven or patchy. The soils which are moderately saline have EC in between 8-15 dS/m, where salts are fairly visible and growth are very patchy. The soils which are strongly saline have EC more than 15 dS/m and salt are widely spread, growth almost nil or very poor.

In the main Indus basin alongside the river, the soil is silty and sandy loam or loamy. Outside this area, soils are calcareous, loamy and silty clay with weak structure and good porosity. The pH is generally in the range of 7.8 to 8.2 and organic matter is about 0.3 to 0.6% and N content varies from 0.01 to 0.07%, which seems to be very low.

It has been observed with concern that since the last couple of decades, the cropped areas are declining in Sindh. Statistics reveal that since 1980, the total cropped areas of other provinces i.e. Punjab, NWFP and Balochistan have increased by 9.83, 5.01 and 7.56%, respectively. But such areas in Sindh have decreased by about 2.31 %, and as far as irrigated areas are concerned, data show that Punjab, NWFP and Balochistan have increased by 15.8, 13,1, and 22.4 5 %, respectively, whereas Sindh has lost about 10.2 % during the period 1980-98. Area irrigated in Sindh is 2.85 mha, of this 2.27 mha are irrigated by canals, 0.13 mha by tube wells and the rest by ordinary wells or other sources. The River Indus has a very high variability in its flow regime. Based on 50 years inflow data, it is estimated that the Indus basin has a mean annual surface water availability of about 141 MAF. Of this 23.0 MAF (or 16%) is available during the six Rabi months from October to March, 44.5 MAF (31%) during first three Kharif months from April to June and 73.36 MAF (52.1%) during the last three Kharif months from July to September. It shows that 42% of the total annual main flow is available during the two months, July and August. In both the periods of severity, of low and extremes flows, Sindh is the major sufferer, being at the tail end of irrigation system. Both these extreme situations are responsible for the development of twin menace of water-logging and salinity. The extent of water logging and salinity is more pronounced in Sindh than elsewhere in Pakistan. About 70 per cent of the cultivable area in Pakistan is vulnerable to water-logging and salinity is in Sindh. As a downstream region, Sindh is at the receiving end of 80 million tons of salt together with 120 million cubic meters of salts annually from the upstream regions of its course. Near to the region of Arabian Sea also contributes to the salinity of ground water. Out of the total cultivable command area of 13.45 million acres in the Sindh Province, only 1.85 million acres are under the treatment of fresh non-saline ground water. In such an environment, water-logging arising from insufficient management of canal irrigation and inadequate drainage practices aggravate the salinity problem by raising the ground water table.

In Sindh, the areas cultivated by canals declined from 6.6 million acres to 5.3 million acres during the year 1997-98. Salinity and water-logging has affected the Sindh Province more than 57 per cent of the cultivable land of Sindh is under water-logging, whereas 41 per cent is under the influence of salinity. The Eucalyptus plant may tolerate salinity upto 10 mS/cm, but its cultivation has many advantages and disadvantages. This plant generally absorbs high quantity of saline water through its root and thus helps in reducing the salt from that lands. This situation makes the soil fertile for growing other economical plants. Field crops grown by man for food, fibre and fodder for animals. The land area available to him are limited, thus there is a need to grow more from each piece of land available to him to feed the ever increasing population, much of the land in Sindh is deteriorating very fast due to duel menace of water-logging and salinity. Research scientists in Sindh have made definite advance during the last 2 to 3 decades. Many new improved varieties with higher yields and quality have been developed. Chemical control of insect, pests diseases have proved useful in reducing losses due to their attack. However, there is a need to apply efficient production technology to obtain sufficient yield of crops in order to improve the growth of crops in salt-affected land.

In Sindh, crop fields are irrigated through the help of three barrages i.e. Sukkur, Guddu and Kotri. The main crops which are grown in Sindh are wheat, rice, bajra, maize, jowar, barley, gram, lentil, mung, guar, cotton, sugarcane, sunflower, safflower, soybean, rape and mustard, groundnut (peanut), linseed, sesamum, castor, chillies, matter, fodder, potato, cowpea, red gram (arhar), clover, berseem, date palm, carrot, onion, tomato.

The soil needs management practices and fertilization. Addition of farm yard manure, green manure through legume crops is necessary to improve the soil conditions. Along with manure and N,P,K fertilizers are very useful to increase the crop productivity by improving the physical and chemical properties of the soil. Irrigation is also essential for the growth of the crops. Application of water to soil for the purpose of supplying moisture essential for plant growth. Crop water use is usually expressed in acre inches. An acre inch is the amount of water required to cover one acre of land with one inch of water.