Efficient Water Application Methods for Growing Paddy in the Indus Basin

Transcription

1 Efficient Water Application Methods for Growing Paddy in the Indus Basin MUHAMMAD AKRAM KAHLOWN 1 AND ABDUR RAOOF 2 ABSTRACT Water shortage in the Indus Basin has necessitated the development of efficient water use methods for growing major crops. Paddy is the major cereal crop, which consumes maximum quantity of water and is grown on an area of 2.52 million hectares in the basin. Under traditional agronomic and water use practices (irrigated puddled paddy fields), the farmers apply much more water for paddy crop than the actual requirements. This leads to excessive evaporation losses from the already scarce resource. Growing paddy on beds and furrows is an alternate, which utilizes much less water. In order to evaluate the water saving from bed and furrow irrigation method for paddy cultivation and to determine the extent of weed infestation and salinity build up, field trials were conducted by the Pakistan Council of Research in Water Resources (PCRWR) during three Kharif seasons (2001, 2002, and 2003). The results revealed that the water use efficiency of rice under bed and furrow systems can be raised up to 0.39 kg/m 3 of water compared to 0.20 kg/m 3 commonly obtained under the traditional flood irrigation method. In addition the infestation of weeds was found much less and there was non-significant evidence of salinity build up on beds compared with the traditional method. Keywords: Paddy, Bed and furrow, Water use efficiency, Soil salinity, Weed growth. 1. INTRODUCTION Pakistan is a country with limited water resources. Per capita water availability has decreased from 5600 m 3 to 1200 m 3 during the last fifty years (Kahlown and Majeed, 2002). The availability of water for agriculture sector has been seriously affected both in quantitative and qualitative terms because of increasing demand of both agriculture and non-agriculture sectors and disposal of untreated industrial and domestic effluent into fresh water bodies. 1 ICID WatSave Innovative Water Management Award Winner (2003), Chairman, Pakistan Council of Research in Water Resources, Khyaban-e-Johar, kahlown@hotmail.com and pcrwr@isb.comsats.net.pk 2 Regional Director, Regional Office, PCRWR, Lahore, ropcrwr@lhr.comsats.net.pk 1

2 Surface irrigation is the most widely practiced irrigation method in the world but its efficiency is usually between 40 to 60% (Kruse and Hermann, 1977). Theoretically a properly designed surface irrigation system should be able to achieve application efficiency up to 70 to 85% (Merriam and Keller 1978). Low irrigation efficiency is usually due to high spatial and temporal variability of soil properties and method of irrigation used. As a result of the former, soil infiltration characteristics are not accurately known and thus irrigation management is poor. The inefficient water use practices have caused the problems of waterlogging, salinity and soil fertility. Among the gravity irrigation methods, furrow irrigation is the most efficient irrigation method as compared to basin or border methods. Surface irrigation techniques can be further improved by developing crop specific layouts based on groundwater depth and quality. Improved surface irrigation methods are helpful to control waterlogging and salinity, and to increase water use efficiency. Kahlown et al. (1998) concluded that bed planting not only ensured better yield of cotton and wheat during normal and wet years but also saved about 30% of irrigation water as compared to level basin. Several researchers (Borrel et al., 1997; Dunn et al. 2004; Hossain et al., 2004.) showed that rice can be grown on bed-and-furrows, with less water than flooded basins. Paddy is the major cereal crop after wheat in Pakistan. This crop is grown on an area of 2.52 million hectares (Mha) with an annual production of 5.02 million tons and yield of 1994 kg per hectare (MINFAL, 2006). It contributes about 10% of the total export earnings. Depending upon the water availability, paddy can be grown in any part of the country from sea level to 2500 m high fields (Federal Water Management Cell, 1997). Pakistan has favourable climate and fertile soil for expanding the paddy production, but water is the only limiting factor both in bringing additional area under paddy and increase per hectare yield. On the other hand, the present water use practices for growing paddy are wasteful. Huge quantity of water is wasted during the land preparation and meeting the actual plant evapotranspiration requirements, which lead to excessive surface runoff, evaporation and deep percolation. It is observed that farmers generally apply more water to paddy field to control the weed germination than what is needed for meeting the crop water requirement. The demand for paddy is increasing with rapidly growing population whereas per capita water availability is decreasing. Therefore, the future of paddy production in Pakistan would mainly depend on developing and adopting conservation strategies and efficient water use methods. Growing of paddy on bed and furrow is an option, which utilizes less water without affecting the yield. 2. OBJECTIVES The general purpose of this study was to increase the water use efficiency in paddy production. The efficient methods developed for cultivation of cotton and wheat was needed to be tested for cultivation of paddy. The specific objectives of the study were: to optimize the design of bed and furrow method of irrigation to maximize water saving and crop yield; and to evaluate the changes in salinity and fertility levels in the soil under bed and furrow irrigation method. 2 2

3 3. METHODOLOGY During 2001, the study was conducted at the PCRWR Lahore Research Station. In 2002 the study was conducted on the Monoo Farm about 6 km from Lahore and in 2003 it was conducted on Inam Elahi farm at Sheikh Dakot Village, about 13 km from Lahore. Table 1 presents results of the textural analysis of soil samples collected up to 90 cm depth at every 15 cm interval. Based on results obtained, the textural class of the experimental sites was classified as clay loam. Table 1. Soil analysis of the experimental sites Depth (cm) Sand % Silt % Clay % Textural Class PCRWR Research Station Loam Clay Loam Clay Loam Clay loam Monoo Farm Trial Site Loam Clay Loam Clay Loam Clay loam Inam Elahi Farm Trial Site Clay loam Clay loam Clay loam Clay loam There were three replications of each of the bed-and-furrow treatments as indicated in Table 2. Land in the bunded basin areas and the bed-and-furrow areas was leveled prior to these studies. The beds and furrows were formed with tractor-mounted equipment, which is available in most parts of the Pakistan. This equipment reduces cost of constructing these beds and furrows to a small fraction of the amount paid to laborers to construct them manually. The furrows were compacted by pounding the soil with a metal block attached to a wooden handle. A wheel-type packing device could achieve similar packing and leave the furrow bed smoother. The objectives of the packing included smoothing the furrow and reducing its friction coefficient so the water could move more quickly and with less head loss from the supply side to the far side of the field and thereby improve the uniformity of the irrigation. The furrows with smoother perimeters also have water levels at the far end of the furrow, which are closer to those at the supply end during the rest of the application time. A rain gauge and an evaporation pan were placed at each site to help decide when to irrigate. 3

4 Table 2. Details of bed and furrow configuration used in field trials Treatment Treatment Description Number Bed & Furrow Configuration Rice Plantation PCRWR Research Station (2001) T1 Bed 30 cm and furrow 15 cm with depth of 22 cm T2 Bed and furrow each of 30 cm with depth of 22 cm T3 Bed 30 cm and furrow 15 cm with depth of 22 cm and one in furrow T4 Flooded Basin: Traditional transplanting on puddled soil (control) Monoo Farm Trial Site (2002) T1 Bed and furrow each of 30 cm with depth of 15 cm T2 Bed and furrow each 30 cm with depth of 15 cm and one in furrow T3 Bed and furrow each 22 cm with depth of 15 cm T4 Bed and furrow each 22 cm with depth of 15 cm and one in furrow T5 Flooded Basin: Traditional transplanting on puddled soil (control) Inam Elahi Farm Trial Site (2003) T1 Bed and furrow each of 30 cm with depth of 15 cm T2 T3 Bed 30 cm and furrow 22 cm with depth of 15 cm Bed and furrow each 22 cm with depth of 15 cm and one in furrow and one in furrow T4 Bed and furrow each 22 cm with depth of 15 cm T5 Bed and furrow each 22 cm with depth of 15 cm with furrows compacted T6 Flooded Basin: Traditional transplanting on puddled soil (control) In the last two years of the study, data on flow rate and time of application was measured from farmers fields adjacent to study trails. Their water use and yields of these fields provided the data listed under Basin flooding in 2002 and Cutthroat flumes and timers were used to measure flow rates into the farmers basins and the bed-and-furrow plots. Super Basmati paddy variety was sown in nurseries 4 4

5 at the end of May and was transplanted into the beds and furrows. Amount of water applied in each irrigation for each treatment was measured. The yield, water use and water productivity values given for the bed-and-furrow treatments in subsequent tables are averages of these three replications. The values given for the much larger adjacent fields, which were irrigated by farmers, are not replicated. Fertilizer was applied to all plots including the farmers fields at the NPK rate of kg/ha respectively as recommended by the Punjab Agriculture Department. The phosphorus, potash and half of the nitrogen were applied before transplanting. The rest of the nitrogen was applied about 50 days later. Zinc sulfate (20%) was applied at the rate of 25 kg/ha about one month after planting to avoid zinc deficiency, which is common in this area. To control weed growth during the initial stage of the rice crop, a weedicide was applied 4 days after transplanting at the rate of 2.5 liters/ha. Razex granular was applied at the rate of 24 kg/ha. Yields were measured on a whole plot basis. 4. RESULTS AND DISCUSSIONS Calculations using pan evaporation and other climatic data indicated that the seasonal evapo-transpiration for rice is about 60 cm of water. Total water applications ranging from 83 to 151 cm indicated that there is a potential for significant reduction in the use of water for rice production. 4.1 Water Use Efficiency The amount of water applied to the bed-and-furrow system was generally 10 to 30% less than the amount applied by farmers to their flooded basins (Table 3). In 2001 and 2003 the yields on the bed-and-furrow systems were from 1 to 38% higher than on the flooded basins. However in 2002 the farmers flooded basin yields slightly increased than those on the bed-and-furrow systems. The water productivity on the bed-and-furrow systems always exceeded those on the flooded basins. Previous studies (Ali and Sabir, 1974; Kahlown et al., 2000) indicated that yields were generally correlated with density of the crop stand. If a row of rice is not planted in the furrow of the bed-and-furrow systems, the previously determined optimum spacing of 22 cm between plants could not be achieved. In the 30 cm bed and 30 cm furrow system, there was less than complete canopy cover of the soil, which tends to reduce yields of most small grain crops (Rafiq and Qureshi, 1991). In the systems with widths of both beds and furrow of 30 cm, rows in the furrows increased the plant density and achieved slightly higher yields than in the comparable bed-andfurrow systems with no row in the furrow. However, when the furrows were only 22 cm wide, adding the row of plants in the furrow did not always increase yield. In fact the best water productivity was found during 2003 with bed 22 cm wide, furrow 22 cm wide and no rice in the furrows. This failure of rice in the furrows 5

6 Rice seedlings transplanted on beds (30 cm) and furrows (22 cm) Rice paddy growing on beds and furrows 6 6

7 Table 3. Water use efficiency and paddy yield as affected by planting Treatment Water Applied (cm) Yield (Kg/ha) Change in Yield (%) WUE (Kg/m 3 ) Water Saved (%) PCRWR Research Station (2001) T T T T Monoo Farm Trial Site (2002) T T T T T Inam Elahi Farm Trial Site (2003) T T T T T T to increase yields may have been due to less uniform (end to end) irrigation, and/ or the fact that the rice plants in the furrow were lower and had less access to sunlight. The natural tendency of plants spaced more widely to grow more tillers may also have helped achieve the needed leaves and heads in the bare furrow plots. The optimum plant geometry appears to be no roots and crowns in the furrows to hinder water movement, but tillering from plants on the beds to achieve reasonably complete canopy cover during the latter part of the season. Beds 30 cm wide coupled with furrows 22 cm wide may also be a good candidate for achieving optimum irrigation uniformity and crop production. While raising the water productivity of rice from 0.20 kg grain/m 3 water to 0.39 can be a substantial improvement for the 7

8 farmers, major potentials for improvement still exist. Water use figures range from 151 cm for the highest basin flooding application down to 88 cm for the bed-andfurrow system with compacted furrows (T 5 : 2003 Table 3). A major portion of the water used in the production of rice in flooded basins percolates down through the soil profile. By reducing application of water and keeping the water content of the soil at or below the field capacity, most of the time, deep percolation of the water can be reduced. Growing rice on beds between furrows, rather than in flooded basins enables the farmer to decrease the amount of water used. There was no indication that these reductions in soil water content and associated increases in soil water tension were reducing rice yield. The associated decrease in water content in the soil does not decrease rice yield if the furrows are refilled with water, on the day after free water left the furrows. This change in irrigation practice almost doubled the water productivity. 4.2 Weed Growth The weed count data showed that weed infestation was not a serious problem with bed and furrow method (Table 4). Weed density was the minimum with traditional puddled soil (control treatment) because of continuous standing of water in the field. Weed density was relatively higher in bed and furrow irrigated trial sites. However, the weeds can be removed manually or by the use of weedicides and therefore there was no need to apply extra water to control the weeds. The weed growth in other treatments was less due to less space available with furrows and restriction of light for photosynthesis. Table 4. Weed infestation Treatment PCRWR Research Station (2001) Weed Density (Weed Plants/m 2 ) Monoo Farm Trial Site (2002) Inam Elahi Farm Trial Site (2003) T T T T T5-8 9 T

9 Table 5. Pre-sowing and post-harvesting salinity and sodicity ph ECe (ds/m) SAR Depth (cm) Pre Sowing T1 T2 T3 T4 T5 T6 Pre Sowing T1 T2 T3 T4 T5 T6 Pre Sowing T1 T2 T3 T4 T5 T6 PCRWR Research Station (2001) Monoo Farm Trial Site (2002) Inam Elahi Farm Trial Site (2003)

10 4.3 Soil Salinity and Sodicity To evaluate the changes in salinity and sodicity of soil profile, the soil sampling was carried out at each trial site. The pre and post transplanting salinity and sodicity data indicated that salt concentration decreased in almost all sampled layers under each treatment except the study conducted at Inam Elahi Farm during 2003 (Table 5). It was observed that rainfall in the year 2003 at this site was less than 50% than the normal. However, the overall salinity content was lower than the threshold value. The highest leaching of salts was observed under control condition because of higher amount of irrigation water applied on this treatment, which caused more deep percolation and leaching of salts from the root zone. The data further revealed that there was no considerable difference regarding re-distribution of salts among the treatments. 5. CONCLUSIONS AND RECOMMENDATIONS On the basis of the field trials conducted during the three kharif seasons, following conclusions and recommendations were made: Higher water use efficiency and paddy yield was obtained with the paddy transplanted on bed and furrow method compared to traditional basin flood irrigation method. Transplanting of two rows of paddy on bed & furrow each 22 cm with furrows compacted furrow gave the highest water use efficiency of 0.39 Kg/m 3 with 32% saving of water. No significant weed infestation was observed if weedicide after first week of transplanting was used. However, the concept of controlling the weeds by applying extra water (a precious commodity) was not found necessary; No significant indication of salinity builds up on beds compared to transplanting of paddy with traditional method was observed. To overcome the scarcity of irrigation water and generate higher crop yield, the bed and furrow method is recommended for paddy cultivation and even planting of other major cops. However, more field investigations may be carried out to test and refine to the configurations of bed and furrows, rice planting system with respect to quality of water and soil, depth of groundwater table, climatic factors etc. REFERENCES Ali, Rehmat and B.A. Sabir, Paddy yield as influenced by varying spacing cum seedling rate per hill. Mona Pub. No. 30 Borell A, Garside A, Fukai S., Improving efficiency of water for irrigated rice in a semiarid tropical environment. Field Crops Res. 52:

11 Dunn, B.W. S.K. Mathews, H.G. Beecher, J.A. Thompson, and E. Humphrey, Growing rice on raised beds in south eastern Australia. 4th International Crop Science Congress Federal Water Management Cell, On Farm Water Management Field Manual, Irrigation Agronomy. Vol-VI, Ministry of Food, Agriculture and Livestock, Govt. of Pakistan, Islamabad Hossain, M.I. C. Meisner, J.M. Duxbury, J.G. Lauren, M.M. Rahman, M.M. Meer and M.H. Rashid, Use of raised beds for increasing wheat production in rice-wheat cropping systems. 4th International Crop Science Congress Kahlown, M.A., and Majeed, A., Water Resources Situation in Pakistan: Challenges and Future Strategies. Science Vision Quarterly, Vol.7 No.3 & 4, Jan-June 2002 Kahlown, M.A., Raoof, A., and Hanif, M, Rice Yields as Affected by Plant Densities. Mona Reclamation Experimental Project, WAPDA, Bhalwal, Pub. No. 238 Kahlown, M.A., Raoof, A., and Hanif, M., Rice yields as affected by plant densities. Mona Reclamation Experimental Project. Pub. No. 238 Kahlown, M.A., Shafique, M.S. and Iqbal, M, Improved Irrigation Methods for Efficient use of Irrigation Water under different Water Table Depths. Mona Reclamation Experimental Project, WAPDA, Bhalwal, Pub. No. 231 Kurse, E.G and Hermann, D. F.,1977, Implications of Irrigation System Efficiencies. J. of Soil and Water Conservation. 32(6): Merriam, J.L., and Keller, J., 1978, Farm Irrigation System Evaluation: A Guide for Management. Utah State Univ., Logan, Utah, USA MINFAL, 2006, Agricultural Statistics of Pakistan , Ministry of Food, Agriculture and Livestock (MINFAL), Govt. of Pakistan Rafiq, C.M. and Asad Sarwar Qureshi, 1991, Irrigation techniques to improve application efficiency and crop yield, University of Agriculture, Faisalabad 11