SOIL CHARACTERIZATION OF ROD KOHI AREAS OF D.I.KHAN DIVISION AND STRATEGIES FOR INTEGRATED SOILAND WATER RESOURCES MANAGEMENT FOR SUSTAINABLE PRODUCTIVITY

Abstract

Rod kohi irrigation farming system is a peculiar system of farming being practiced in Piedmont plains of D.I.Khan division (NWFP) Pakistan covering almost 60% of cultivated area. The major constraint is the use of Rod kohi water which is unpredictable and highly variable in quantity and distribution both in time and space. Rod kohi soils are particularly confronted with problems of soil productivity, soil surface sealing, amount of irrigation water application and nutritional requirement of crops. In this regard, a series of experiments were conducted to understand the problems related to Rod kohi soils of D.I.Khan division and develop strategies for addressing them. The first three chapters deal with general introduction of Rod kohi area, review of literature and methodologies used in different studies. Chapter IV relates to the characterization of soils of Rod kohi area. Eighty seven soil samples from different mozas (villages) were collected to make inferences regarding the nature of the soils, salinity/ sodicity problems and productivity status. It was found that 50.57% of soils were medium textured while 45.98% samples were fine textured and only 3.45% soils were moderately coarse textured. All soils were alkaline in nature with pH ranging from 7.7 to 8.6. The ECe varied from 0.75 to 8.00 dS m-1 with a mean value of 3.156 dS m-1 and SAR was in the range of 3.00 to 12.78. Almost 74.71% soils were normal, 13.79% of soils saline while 5.75% soils were sodic and another 5.75% of samples were saline sodic. Similarly 74.71% of samples were strongly calcareous while 25.29% samples were moderately calcareous. Almost 83.53% samples were deficient in organic matter while 16.47% samples contained marginal amount of organic matter. All samples were deficient in mineral N, while 89.41% samples were deficient in P, however, 70.59% samples contained adequate amount of K. Agriculture in Rod kohi areas totally depends on hill torrent flow that is un-predictable in terms of timing, magnitude and frequency thus making scheduled irrigations impossible. Farmers in Rod kohi area usually over irrigate their fields which results wastage of water. Experiment regarding determining the optimum amount of water required for maximum production in Rod kohi areas has been discussed in Chapter V. Different quantities of Rod kohi water viz 15-25 cm, 25-35 cm, 35-45 cm, and 45-55 cm depth were applied to fields of variable textures i.e. silty clay loam, silt loam and loam, to see their effect on the yield of wheat, application efficiency (Ea), water use efficiency (WUE), moisture and bulk density (BD) of soils. It was revealed that grain yield of wheat increased with the increment of irrigation water in all types of soil and maximum grain yield was obtained after the application of 35-45 cm irrigation depth; beyond this the yield declined suggesting that 35-45 cm depth of irrigation is the optimum water requirement for wheat in Rod kohi areas of D.I.Khan. Amongst textural classes, the highest grain yield was achieved from loamy soil followed by silty loam and silty clay loam soil. The application efficiency of irrigation water differed significantly among different textured soils as well as depth of water applied and their interaction. It decreased as the depth of irrigation water increased. The maximum Ea was recorded with the application of 15-25 cm irrigation. Hence, it is suggested that water should be applied in such amount that is efficiently utilized and the crop yield is also not affected. The silty clay loam soil had the highest Ea (63.75%) while loamy soil has the lowest (42.24%) and silt loam was at intermediate position (50.43%). In water-deficient environments, crop productivity is determined by the amount of water available and water use efficiency (WUE) of crop. The WUE was determined on grain yield basis per mm water application. The results revealed that WUE was significantly influenced by the volume of water applied as well as soil texture and their interactions. It ranges from 5.917-13.627 kg ha-1 mm-1 being the minimum for 45-55 cm depth of irrigation and the maximum for 15-25 cm depth suggested that the water use efficiency (WUE) was inversely related to irrigation water volumes. It decreased linearly as irrigated water volumes increased. The loamy soils had higher (10.238 kg ha-1 mm-1) while silty clay loam soils had lower (8.914 kg ha-1 mm-1) WUE and intermediate values (9.244 kg ha-1 mm-1) of WUE were recorded for silt loam soils. The soil moisture content determines the success or failure of crop production in Rod kohi agriculture where yield of crop is significantly affected by the availability of moisture in the root zone during growing season. The soil moisture content was determined at three stages viz before flood, at the time of sowing and after harvest of crop at different sites having variable textured soils and amount of water applied. The silty clay loam soil retained highest moisture content followed by silt loam and loam. The highest soil moisture content was found at the time of sowing at all textured soils this caused the decreased at the time of harvest of the crop, while the lowest moisture content was recorded in samples collected before flood. The moisture content in the soils increased with the increase in irrigation depths. The bulk density (BD) of different textured soils which were applied different volumes of water was also determined at three stages i.e. before flood, at the time of sowing and after harvest of crop. It varied in different textured soils but the differences were not significant. The loamy soils had the highest BD, while silty clay loam soils gives the lowest but with no statistical difference. Soil surface sealing is a major problem in Rod kohi soils when rainfall occurs after sowing of seed and before germination. In this work, different textured soils viz silty clay loam, silt loam and loam were subjected to variable simulated rainfall intensities (5.0 mm, 10.0 mm and 15.0 mm) after sowing of the wheat seed. Different soil crust management practices i.e. hand hoeing, crop residue cover and application of FYM were applied to reduce crust development and increase seedling emergence and yield of wheat. The results of our observations are presented in chapter VI. It was inferred that the soils of Rod Kohi area are prone to crust development irrespective of texture and rainfall intensities which retarded seedlings emergence and consequently reduced grain yield of wheat. Soil crusting reduced 35.86 to 52.94% seedlings germination. The silty clay loam soil was more susceptible to crusting as compared to silty loam and loamy soil. Amongst rainfall intensities, the 5.0 mm rainfall intensity significantly reduced seedlings emergence at all textured soils, reflecting greater soil crust strength as compared to 10.0 mm and 15.0 mm rainfall. Different soil crust management practices improved seedlings emergence significantly at all types of soils. The significantly highest germination count was recorded in manual hoeing followed by crop residue (CR) and FYM. Similarly, the grain yield of wheat was significantly affected by different rainfall intensities and soil crust management practices in all soils. The significantly lowest grain yields were noted with 5.0 mm rainfall intensity at all the three locations, whereas the highest yield was found in 15.0 mm rainfall intensity. The significantly highest grain yield was achieved in loamy soil followed by silty loam soil while the lowest in silty clay loam soil. The results indicated that manual hoeing proved most effective in enhancing seedlings emergence and increasing the grain yield followed by CR and FYM. The combined data of three locations showed that increase in grain yield from FYM, CR and manual hoeing over control was 48.84%, 60.46% and 73.33% respectively. Studies pertaining to nutritional requirement of wheat under Rod Kohi conditions are reported in chapter VII. Field trials were conducted on silty clay loam and loamy soils for two consecutive years during 2006-07 and 2007-08. Fertilizers rates included NPK @ (i) 0-0-0, (ii) 20-0-0, (iii) 40-20-0, (iv) 40-20-10, (v) 60-30-20, (vi) 80-40-30 and (vii) 100-50-40 kg ha-1. Amongst different yield contributing parameters, plant height, number of productive tillers m-2, ear length and grain yield were significantly affected by application of different rates of NPK at both locations. All parameters increased with the increment of fertilizers rates. The maximum plant height (78.88 cm), number of productive tiller m-2 (378.40) and longest spikes (9.265 cm) were recorded in plots receiving NPK @ 100-50-40 kg ha-1 followed by NPK@ 80- 40-30 kg ha-1. Similarly the highest grain yield was achieved by the application of NPK @ 100-50-40 kg ha-1 closely followed by NPK@ 80-40-30 kg ha-1 and both were significantly similar. Computing the economic of fertilizers application revealed that the most economical dose of fertilizers for achieving maximum grain yield of wheat under Rod Kohi conditions of D.I.Khan is NPK @ 80-40-30 kg ha-1 it may be attributed to the better growing conditions and residual effects of NPK. In silty clay loam soil 8.33 to 27.91% increase in grain yield was noted due to fertilizers application while in loamy soil, the increase was 8.43 to 38.62%. All parameters had higher values at loamy soil against silty clay loam soil.