Estimation of Water Requirements for producing Irrigated Rice in River Valley Bottom at Central Agricultural Station, Kumasi Ghana

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1 Vol. 1 Issue, pp: (5-6), June Available online at: International Research Journal of Agricultural and Food Sciences Article Number: PRJA Copyright 2016 Author(s) retain the copyright of this article Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution 4.0 International License. Full Length Research Paper Estimation of Water Requirements for producing Irrigated Rice in River Valley Bottom at Central Agricultural Station, Kumasi Ghana Ekow Gaisie *1, Adams Sadick 2, Gabriel Quansah 2 and Calys-Tagoe Edward 1 Soil and Water Management, Soil Research Institute, Kumasi, Ghana. 2 Department of Soil Chemistry and Mineralogy, Soil Research Institute, Kumasi, Ghana. Department of Soil Fertility, Soil Research Institute, Kumasi, Ghana. *Corresponding author. ekow_2006@hotmail.com Received: 17 February 2016; Accepted: 2rd May 2016 Abstract The study was carried out to determine water requirements and fertility levels for producing irrigated rice in the valley bottom area of the Kwadaso Central Agricultural Station. Meteorological data such as rainfall, temperature, humidity, wind speed and sunshine hours, obtained from local meteorological station, were used to determine the irrigation requirement through CROPWAT model using Penman Monteith equation for producing rice in the dry season (2014). Water samples was collected from upper course, middle course and lower course of the stream as well as irrigated field for analysis and Composite soil samples were randomly collected from the field at a depth of 0-15 cm from 20 sampling spots. Water and soil quality parameters such as ph, ECiw, HCO -, CO 2-, SAR, SSP, RSC and KR and N, P, K, Ca, mg, Na and Organic carbon were also used to determine the quality levels of the irrigated water and soils. Crop evapotranspiration and irrigation requirement of rice varied from 4.00 to 5.2mm/day with a total of 647mm for the growing season, and a total of 812mm for the growing season. Though the irrigated water quality was suitable for irrigation, the soil quality level was low and required soil management practices to improve the soil quality. The study also showed that all the water quality parameters were within the permissible limit and there are no significant difference between the values in the upper course, lower course and the irrigated field. Keywords: Irrigation water quality, Gwashen, Evapotranspiration and Enabehin.

2 54 Int. Res. J. Agric. Food Sci. INTRODUCTION The rapid population growth worldwide and the high demand for water are of great concern. Water is important for plant growth and food production. In arid and semi-arid regions, precipitation is low and therefore water is scarce (Arku et. al., 2011) There is the need to conserve the available water resources (Arku et. al., 2011). Agriculture accounts for about 70 percent of all freshwater withdrawn from lakes, waterways and aquifers around the world (Bastiaanssen et al., 2000). The figure is closer to 90 percent in several developing countries, where roughly threequarters of the world s irrigated farmlands are located (WUCOLS, 2000). According to Radwan et al. 2010, since landscape and ornamental plants irrigation accounts for 40 to 60% of total household water consumption conserving and reducing the amount of water used for landscape and ornamental plants irrigation is critically important. Generally, rice production in Ghana is an upland activity by subsistent farmers and a few commercial and co-operative growers (Opoku-Duah et. al., 2000). The production system is mainly rainfed, often hampered by unreliable rainfall, for instance, wide variations in both the temporal and spatial distribution, and low precipitation amounts. Besides, tropical upland soils are often poor, due mainly as a result of soil erosion, also resulting from the interactive effect of high rainfall intensity and continuous seasonal cropping (Opoku-Duah et. al., 2000). This situation leads to average low yield of rice (<2.5t/h) in Ghana (Opoku-Duah et. al., 2000). Apart from this, the need for more agricultural lands due to increasing population requires the conversion of less favorable lands (e.g. inland valleys) into farming plots. The use of inland valleys (i.e. valley bottoms) for rice production presents a particularly viable option for three main reasons. Firstly, water is available in valley bottoms for most part of the year in Ghana. Secondly, rice has enormous capacity to thrive under waterlogged conditions. Finally, inland valleys are naturally fertile. Despite the inherent adequacy of water and fertility potential of tropical lowlands (Opoku-Duah et. al., 2000). This study was initiated by Soil Research Institute of Council for Scientific and Industrial Research, Ghana, and supported by SAWAH project to increase rice production in Ghana. Therefore, this study was carried out to assess the crop water requirement of the irrigated rice and qualitative suitability of water resources of inland valley at SAWAH rice field in the Ashanti Region of Ghana. MATERIALS AND METHODS Location and Climate The study area is located at the Central Agricultural Station (CAS), Kwadaso in the Ashanti Region of Ghana (Figure 1). The geographical location of Kwadaso lies in Latitude 6.42 o N and Longitude 1.4 o W with an altitude of 284m above mean sea level.

3 Gaisie et al 55 Figure 1: Location of Study Area Rainfall and stream water was the main source of water for irrigation. The stream, locally called Gwashen, stretches from the southern part of the study area (upper course) to the northern part (lower course). The stream is one of the tributaries of river Offin which passes through Enabehin in the Ashanti Region of Ghana (Figure 2)

4 56 Int. Res. J. Agric. Food Sci. Figure 2: Location of Sampling Site The study area is within the tropical climatic zone with a bi-modal rainfall peaks (i.e. major and minor seasons). The major season normally starts in March; reaches a peak in July and drops sharply in August whilst the minor season starts in September with the lowest occurring in late November. Thereafter, there is an extensive dry period from December to February during which small amounts of rain normally (below 10mm) are received. Mean monthly temperatures remain high throughout the year only falling around 24 o C in August. February and March are the hottest (nearly 28 o C) recorded months. Absolute minimum temperatures of around 20 o C are usually recorded in December and January with absolute maximum temperature of about o C occurring in February and March Field Study and Data Collection The field experiment was conducted in 2014 on rice to estimate crop water requirements in dry season. This was done using CROPWAT software model (Adriana and Cuculeanu, 1999). Soil Sampling and Analysis Composite soil samples were randomly collected from the field at a depth of 0-15 cm from 20 sampling spots. Soils were analyzed for organic carbon, total nitrogen, available phosphorus, exchangeable calcium, magnesium, potassium and sodium, ph and soil texture as described by Ibitoye (2006).

5 Gaisie et al 57 Water Sampling and Analysis Three () locations on the stream (upper, middle and lower course) and the irrigated field were selected as sampling sites. From each sampling location, three sets of water samples were collected. This was done during the dry season. The bottles used for sampling were cleaned with dilute hydrochloric acid (HCl) and rinsed repeatedly with deionized water as suggested by De (1989). The bottles were kept air tight and labeled properly for identification. Stoppering of the bottles was done quickly to avoid aeration during sampling. Electrical conductivity (EC iw ) and ph of the samples were measured on-farm using portable EC-meter and ph-meter respectively. The samples collected from the study area were carefully transported in an opaque bag to SAR Ca Na CSIR-Soil Research Institute s laboratory, Ghana and kept in a refrigerator for analysis. Sodium (Na + ) and potassium (K + ) were determined by a flame photometry (Jackson, 1967); Calcium (Ca 2+ ), magnesium (Mg 2+ ), by Atomic Absorption Spectrophotometer (AAS) (Jackson, 1967; Page et al., 1982); bicarbonate (HCO - ) and carbonate (CO 2- ), by titration method (Jackson, 1967). For current irrigation water quality assessment, sodium adsorption ratio (SAR), soluble sodium percentage (SSP), residual sodium concentration (RSC) and Kelly ratio (KR) were monitored. According to Richards (1954), sodium adsorption ratio (SAR) is expressed as: mg Todd (1980) defined soluble sodium percentage (SSP) as: SSP Ca Na mg K Na K Eaton (1950) also defined residual sodium concentration as: RSC HCO CO Ca mg and Kelly s ratio (KR) (Kelly, 196) described as: KR Na mg 2 2 Ca All ionic concentrations were in milli equivalent per liter (meq/l).

6 58 Int. Res. J. Agric. Food Sci. RESULTS AND DISCUSSION Irrigation Water and Soil quantity assessment Table 1 represents the soil nutrients from composite samples which were used to quantify the true status of the soil in the study area. The simulated values of reference evapotranspiration (ETo) through CROPWAT model using Penman- Monteith equation, at the study area is shown in the Table 2 along with the meteorological parameters for the crop season. Table represents the crop water requirement of the rice. The water balance analysis for study the area is also presented in Figure. According to USDA soil textural classification chart, the experimental soil was predominantly coarse textured, ranging from loamy to sandy loam in the surface horizons (Table 1). Soil ph is the measure of sodicity, acidity, basicity and neutrality. It is an important estimation for soils as soil ph has a considerable influence on the availability of nutrients to crops and also affects microbial population in soils. Most nutrient elements are available in the ph range of and also crop yields are normally high in soils with ph values between 6.0 and 7.5 (FAO, 2006). Soil ph of the samples ranged from 5.26 to 5.92 (Table 1). These are considered as acidic respectively. Generally, the ph values of all the soils were below the optimal ph range for high crop yields. Liming is therefore recommended to increase the ph levels of the soils. Generally, soil organic matter content decreased with increase in depth i.e. down the profile. Organic Carbon content of the soils ranged from 1.1% to 1.59% and could be described as low (FAO, 2006). Low Organic carbon is an indication of low fertility and high fragility of soils. However, to maintain the fertility of the soils, management practices that promote accumulation of organic matter are recommended, for example cover cropping, soil and water conservation, manure application etc. Available phosphorus levels ranged from 2.18 to.75ppm soil. Phosphorus levels less than 10ppm soil are described as low, between 10 and 20ppm soil as moderate and above 20ppm soil as high (FAO 2008). All the soils were observed to be low and would require P fertilization. Exchangeable calcium levels are directly proportional to the soil ph levels i.e. high ph levels result in high calcium levels. The exchangeable calcium ranged from 0.99 to 1.4 cmolkg-1 soil. This is described as low (FAO, 2006) The reference crop evapotranspiration (ETo) ranged from.29 to 5.02mm/day in the month of July and March, respectively. The increase in ETo in August and April can be explained by the reduced rainfall along with rising temperature during dry period. Thus, the rainfall and air temperature has a direct effect on the reference crop evapotranspiration (ETo). Table 2 also reveals that there is strong relationship between solar radiation and reference evapotranspiration (ETo). Solar radiation remains high during August, September, October, January, February, March and April, and ETo follows the same pattern. The crop water requirements of rice during the year under review varied from 2.18 to 5.47mm/day (Table ). The high amount of irrigation water used during land preparation in the rd decade could be due to low precipitation during that period. It showed from the results that between January and February, August and September and December and January ETo were higher than precipitation. This implies that irrigation was necessary to grow crops during these periods of non-availability of sufficient amount of precipitation and high atmospheric evaporative demand by crops and the optimum planting dates of the crops were March and September in the major and minor season respectively. Also from February to August and September to December in the major and minor season, precipitation was much higher than ETo. There was abundant supply of precipitation during these periods and might cause sudden flood if the irrigation water is not properly managed. Irrigation water quality assessment The ph of the study area was generally acidic ranging from 5.61 to 6.41 with an average of This average was identified to be within the acceptable range of irrigation water quality (WHO, 2004). Primary effect of high ECiw water on crop productivity is the inability of the plant to compete with the ions in the soil solution of water. The higher the ECiw, the less water is available to the plants, even though the soil may appear wet, leading to low productivity (Adams et. al., 2014). From table 4, ECiw varied from 0.05 to 0.25ds/m with average value of 0.15ds/m, which was suitable for irrigation purpose (DoE, 1997 and WHO, 2004). ECiw and Na + play a very important role in suitability of water for irrigation (Rao, 2005). Soil containing large contents of Na + with HCO - or Cl - /SO4 2- turns a soil alkaline or saline respectively (Rao, 2005). Higher Na + content in irrigation water causes an increase in soil solution osmotic pressure (Rahman et al., 2012). Since plant roots extract water through osmosis, the water uptake of plants decreases. The osmotic pressure is proportional to the salt content or salinity hazard (Rahman et al., 2012). The salt, besides affecting the growth of plants directly, also affects the soil structure, permeability and aeration, which indirectly affect plant growth. Furthermore, high Na + and elevated carbonate content also cause displacement of exchangeable Ca 2+ and Mg 2+ from the clay mineral of the soil (Rahman et al., 2012).

7 Gaisie et al 59 Thus, an increase of soil ph, nutrient availability and hindered microorganism activity in the soil. Na clay H 2 O H clay Na 2 CO H 2O HCO OH OH Another significant chemical parameter identified for assessing the degree of suitability of water for irrigation was sodium content or alkali hazard, which is expressed as the sodium adsorption ratio (SAR). SAR measures the potential dangers posed by excessive sodium in irrigation water (Alagbe, 2006). According to Richards, (1954) sodium hazard or SAR is expressed in terms of classification of irrigation water as low (S1: <10), medium (S2: 10 to 18), high (S: 18 to 26) and very high (S4: > 26). A high SAR value implies a hazard of sodium (alkali) replacing Ca 2+ and Mg 2+ in the soil through a cation exchange process that damages soil structure, mainly permeability, and which ultimately affects the fertility status of the soil and reduces crop yield (Gupta, 2005). From Table 4 all the water samples from the study area were low (S1 :< 10) and in the excellent range, hence very suitable for crop irrigation (Table ). The samples also had soluble sodium percentage (SSP) in a class range of excellent except samples from the lower course which was close to the irrigated field has good range; this may partly be due to low value of potassium (K + ) in the lower course of the study area (Table ). Average RSC of the study area varied from 2.19 to.09 mg/l with the highest occurring at the middle course. A positive RSC value indicated that the contents of dissolved Ca 2+ and Mg 2+ ions is less that of CO 2- and HCO - (Raihan and Alam, 2008). RSC values were satisfied in the study area. According to Gupta and Gupta, 1987, satisfactory RSC should be less than 5mg/l. In the study area HCO - ranged from 99.4 to mg/l with an average value of mg/l. Irrigation water rich in HCO - content tend to precipitate insoluble Ca 2+ and Mg 2+ in the soil which ultimately leaves higher proportion of Na + and increases the SAR value (Michael, 1992) as: 2 2HCO Ca CaCO H O CO It has also been reported that, although ordinary HCO - is not toxic, it can cause zinc deficiency in rice and this is severe when zinc levels exceeded 2meq/l in water used for flooding growing paddy rice. From the study area the irrigated rice field has zinc levels less than 2meq/l, hence such problem does not exist in the SAWAH irrigated rice field in the study area. However, Kelly (196) suggested that KR for irrigation water should not exceed 1.0. All values satisfy such a restriction; hence a good balance of Na +, Ca 2+ and Mg 2+ is present in the study area. This also indicated a good tilth condition of the soil of the study area with no permeability problem. At the same level of salinity and SAR, adsorption of Na + by soils and clay minerals was greater at higher Mg:Ca ratios. This was because the bonding energy of Mg 2+ was less than that of Ca 2+, allowing more Na + adsorption. This happened when the ratio exceeded 4.0 (Alagbe, 2006). In the study area, the ratio of Mg 2+ and Ca 2+ for all parameters was less than 1.0 (Table 4). Thus, it indicated a good proportion of Ca 2+ and Mg 2+, which maintains a good structure and tilth condition. The presence of excessive Na + in irrigation water promotes soil dispersion and structure breakdown when Na + to Ca 2+ ratio exceeds :1. Such a high Na:Ca ratio (>:1) results in severe water infiltration problems, mainly due to lack of sufficient Ca 2+ to oppose the dispersing effect of Na +. Excessive Na + also creates problems in crop water uptake, poor seedling emergence, lack of aeration, plant and root diseases etc. SAWAH irrigated rice field has no such problem (Table 4). 2 2

8 60 Int. Res. J. Agric. Food Sci. TABLE 1: SOIL NUTRIENTS FROM COMPOSOTE SOIL SAMPLES (2014) Label ph 1:1 P OM N Ca mg K Na Texture ppm % Cmol(+)/kg S Sandy loam S Sandy loam S Sandy loam S Loamy S Sandy loam S Sandy loam S Sandy loam S Sandy loam S Loamy S Loamy TABLE 2: REFERENCE EVAPOTRANSPIRATION AT CENTRAL AGRIC STATION, KWADASO (2014) Month Min Max Humidity Wind Sun Rad ETo Temp Temp C C % km/day hours MJ/m²/day mm/day January February March April May June July August September October November December Average ETo = Reference crop Evapotranspiration computed using FAO Penman-Monteith Method

9 Gaisie et al 61 TABLE : EVAPOTRANSPIRATION AND IRRIGATION REQUIREMENT FOR RICE (2014) Month Decade Stage Kc ETc ETc Eff rain Irr. Req. Irr. Req. coeff mm/day mm/dec mm/dec mm/dec mm/day Nov 2 LandPrep Nov LandPrep Dec 1 Init Dec 2 Init Dec Deve Jan 1 Deve Jan 2 Mid Jan Mid Feb 1 Mid Feb 2 Mid Feb Mid Mar 1 Late Mar 2 Late Mar Late Where N= Nursery, N/L= Nursery/Land preparation, Init= Initial stage, Development stage, Mid= Mid-Season stage, Late= Late season stage, IR= Irrigation Requirement (mm/day), IR= Irrigation Requirement (mm/dec), Kc= Crop Coefficient, ETc= Crop Evapotranspiration (mm/day), ETc= Crop Evapotranspiration (mm/dec). TABLE 4: LIMITS OF SOME IMPORTANT PARAMETER INDICES FOR RATING WATER QUALITY AND ITS SUITABILITY IN IRRIGATION USE Category Water quality indices * Suitable for ECiw (µs/cm SAR SSP irrigation I < 700 <10 <20 Excellent II Good III > Fair IV - >26 >80 Poor According to Ayers and Westcot (1985), Todd (1980) and Wilcox (1955) respectively TABLE 5: SELECTED IRRIGATION WATER QUALITY PARAMETERS (2014) Sample ph ECiw SAR SSP RSC KR Mg:Ca Na:Ca CO 2- HCO - µs/cm % meq/l mg/l mg/l UC MC LC RF RF Mean SE SAR: Sodium Adsorption Ratio, SSP: Soluble Sodium Percentage, RSC: Residual Sodium Concentration, KR: Kelly Ratio, UC: Upper Course, MC: Middle Course, LC: Lower Course, RF: Rice Field, SE: Standard Error

10 62 Int. Res. J. Agric. Food Sci. Figure : Hydrological balance of ETo and precipitation at Kwadaso CONCLUSION SAWAH irrigated rice project in the valley bottom site is primarily rainfed during the major season of the year, except minor and dry season which requires significant amount of irrigation water from the stream. From the results above, it could be concluded that the fertility level of the soil was very low and require management practices that promote accumulation of organic matter are recommended e.g. cover cropping, soil and water conservation, manure application etc. In the months of January and February, August and September and December and January irrigation water was required since no precipitation was experienced during that period. From February to August and September to December, no irrigation water was required since there was significant amount of rainfall. The study also indicated that in terms of water quality the stream is suitable for small-scale irrigation project. The levels of irrigation water quality parameters; ph, EC iw, CO 2-, HCO -, SAR, SSP, RSC and KR are within the acceptable limit which will not cause crop toxicity and salinity problem, unless under extremely poor drainage and or water management practices. CONFLICTS OF INTEREST The authors declare no conflict of interest. REFERENCES Adams S, Quansah GW, Issaka RN, Asamoah E, Nketia K A, Amfo-Otu R (2014). Water requirements of some selected crops in Tono irrigation area. J. of Biodivers. and Environ. Sci. 4(), pp Adams S, Issaka RN, Quansah GW, Amfo-Otu R and Bagna S (2014). Assessment of irrigation water quality of Tono dam in Navrongo, Ghana. J. of Biodivers. and Environ. Sci. 4() pp Adriana MV and Cuculeanu. (1999). Uses of a decision support system for agricultural management under different climate conditions, Abstracts Volume of the 4th European Conference on Applications of Meteorology (ECAM99), Norrköping, Sweden, pp Alagbe SA (2006). Preliminary evaluation of hydrochemistry of the Kalambaina formation, Sokoto Basin, Nigeria, Environmental Geology. 51(1) pp

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