Irrigation Water Productivity of Rice under Various Irrigation Schedules and Tillage Practices in Northern Guinea Savanna Region of Nigeria

The effect irrigation method and tillage on yield and irrigation water productivity of rice was conducted in split plot experiment with three replications during the dry seasons 2012 and 2013 in field conditions at the Lake Geriyo Irrigation scheme farms in Yola, Nigeria. 3 irrigation management: 3, 6 and 9 day interval with 3 tillage practices: zero, shallow and deep soil tillage were studied. Results showed that there were significant differences in paddy yield, harvest index and irrigation water productivity. 6 days interval irrigation management was placed to one group with 3 days irrigation interval on paddy yield and harvest index; higher water productivity of 3.58 and 3.51 kg ha mmwere recorded with 6 days irrigation interval in both seasons respectively. Therefore it can be recommended that 6 day interval irrigation which had better irrigation water productivity and saved up 29% irrigation water be adopted for rice cultivation under clay loam soils of guinea savanna zone of Nigeria.


Introduction
Rice (Oryza sativa L.) is one of the most important staple food crop around the globe and more than half of the world population depends on rice for food calories and protein especially in developing countries.In Nigeria, rice is the sixth major crop in cultivated land area after sorghum, millet, cowpea, cassava, and yam and it is the only crop grown nationwide and in all agro ecological zones from Sahel to the coastal swamps (Olaleye et al., 2004, Akinbile andSangadoyin, 2011).Tuong and Bouman (2003) estimated that by 2025, 2 million ha of irrigated dry season rice and 13 million ha of irrigated wet-season rice may experience water scarcity.Irrigated rice is a great and inefficient consumer of water and in recent years, worldwide, scarcity and competition for water have been increasing.This brought a need for irrigation strategies that produce rice with less water and at the same time improve Irrigation water productivity (IWP).In many places, irrigated agriculture consumes more than two thirds of the available water, as the demand for industrial, municipal and other uses rises, water for agriculture is becoming less available (Gani, 2001).Therefore if food security is to be maintained, ways of increasing the productivity of water must be found (Barker et al., 2000) and one of the ways of saving irrigation water is to use the alternate irrigation (irrigation at intervals) during the rice growing season (Tuong and Bouman, 2003).It should be noted that field water management that saves water often leads to increase in water

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productivity or water use efficiency (WUE) with slight reduction in rice yield (Clemmens et al., 2008) Tillage practices profoundly affect physical properties, it's therefore essential to select tillage practice that sustains physical and chemical requirement for successful growth of agricultural crops.Information is therefore needed on the effect of regulated irrigation and different tillage practices under irrigated rice production.
Reducing water input for rice will change the soil from submergence to greater aeration.These shifts may have profound effects on the suitability of the lowland rice ecosystem.It is important for farmers to know the tillage practice that best sustains soil properties and enhances water productivity.The essence of this study was therefore, to determine the appropriate irrigation intervals and tillage practices for optimal rice grain yield and water productivity in the study area.

Materials And Methods
The experiment was conducted at the Lake Geriyo Irrigation site in Yola North local government area of Adamawa State, Nigeria.The Irrigation Project Site is situated at the North Western part of Jimeta-Yola, North Eastern Nigeria.It lies between longitude 12 0 and 12 0 28' east of Greenwich and latitude 9 0 16' and 9 0 19' North of the equator.The area is between 150 and 180 meters above sea level.It is bounded in North East by River Benue, Jimeta in the South West and Namtari Forest Reserve on the West.It covers an area of 850 hectares.The annual rainfall of the area ranges from 700-1,000mm while, temperature ranges between 15.2 0 -39 0 C (Adebayo, 1999).Relative humidity follows the simple relationship with change of the season while, geological formations of the area include alluvium, basement complex, sedimentary and volcanic rocks (Usman, 2005).The soils of the area is clay loam in texture, moderate bulk density, slightly acidic, very low in organic carbon, total nitrogen, ECEC and available P. The water retention properties of the soils are moderate (Table 1).The rice variety used for this experiment was Faro-44.The experiment was laid out in a Split Plot Design and replicated three times.Each replication contains 9 plots giving a total of 27plots with each plot measuring 3 x 3m.The Main plot factor is Irrigation (I) which has three different levels of irrigation, viz; I0 = 3 days irrigation interval, I1 = 6days irrigation interval and I2 = 9days irrigation interval.The Sub plot factor is Tillage practice (T), which has three different tillage depths, T0 =zero tillage, T1 = shallow tillage (10cm) and T2 = Deep tillage (20cm).The experimental site was cleared of shrubs and stubbles and prepared manually into check basin measuring 3m x 3m with the use of hoe.In reduce tillage plots, seeds were sown without tilling the soil except for making bunds around the basins, and holes for sowing seeds, while shallow and deep tillage plots, were prepared to the required depth using hoe.The seeds were sown by direct seeding using hoe at a spacing of 20cm between rows and 20cm within rows.

Irrigation
Water was pumped from wells using water pump that supply water to the check basin through surface irrigation method.The flow or discharge rate was measured using velocity volume method.Each basin was ponded with equal volume of water at each irrigation period.Q=V/T Where: Q = discharge rate, V = Volume and T= time taken to fill known volume (Trimmer, 1994).
Fertilizer was applied as NPK at the rate of 80 Kg N, 30 Kg P2O and 30 Kg K2O per hectare.First application was carried out at sowing, another at three weeks after sowing (WAS), and the last application was done at six weeks (WAS).Weeds were controlled using paraquat at 25Kg per ha as a pre-emergence herbicide.Later 2-4D was use as selective herbicide to control weeds at the rate of 250ml in 20litres of water per ha (WARDA, 2008).Where obnoxious weeds exist, they were weeded by hoe and for reduce tillage plots weeds were uprooted using hands.

Laboratory analysis
Soil physical and chemical properties were determined using the methods suggested by Ryan et al. (2001).Bulk Density was determined using a short cylinder core of about 5cm long and 5cm diameter and calculated using the expression by Cassel (1982): Total Porosity was calculated by assuming a particle density of 2.65Mgm -3 and then using the expression as given by Childs and Bybord (1969).Available Phosphorus was determined by Bray-I procedure, described by Page et al. (1986).

Field study
The middle one square meter was sampled from each plot and harvested using cutting sickle for paddy yield analysis.The harvested portion was threshed, weighed and represented as paddy yield in kilogram per hectare.Straw of the sampled one meter square was left to dry on the field for about ten (10) days weighed and expressed in kilogram per hectare.Harvest Index was computed as the percentage of the ratio of the economic yield to that of the biological yield.

Data analysis
The data obtained was subjected to analysis of variance (ANOVA).The means of treatment found to be significantly different at p = ≤ 0.5 were separated using the least significant difference method (LSD) (CropStat, 2007).

Results and Discussion
The effect of irrigation interval on paddy and straw yield as well as harvest index was significant (P ≤ 0.01) but, tillage practices and interaction effects were no significant on these parameters in both seasons (Table 2). 3 days irrigation interval treatments produced the highest paddy yield, straw weight and harvest index which are statistically not different from 6 days irrigation interval in both cropping seasons.This is similar to the findings of Tantawi and Ghanem (2001) who reported higher rice yield with 3 days irrigation intervals but, reduced with increase in irrigation intervals.There was no significant difference among the tillage practice; this conforms to the findings of Mathew and Johnkutty (2003) and Gajri et al. (1999) who observed no significant difference in rice grain yield between different tillage treatments.Results for water use (mm) and irrigation water productivity (kg ha -1 mm -1 ) are presented in Table 3.The results reveal highly significant difference (P ≤ 0.01) in these parameters.The water use was higher with three days irrigation schedule (1422.25 and 1387.65 mm), while the least was with 9 days irrigation schedule (888.90 and 882.65 mm) respectively for the two seasons.The irrigation water productivity for the two cropping seasons was higher with the irrigation every 6 days (3.58 and 3.51) while the least (2.70) was recorded from 3 days irrigation schedule.Tillage practices did not affect both water used and irrigation water productivity significantly (P ≥ 0.05).The interaction effect between irrigation interval and tillage practices was significant on irrigation water productivity with 6 days irrigation interval treatments across all tillage practices having the highest IWP in both seasons (Table 4).Better water use efficiency was recorded in the 6 days irrigation interval treatments, while the least was from 3 days irrigation interval.Ghanem and Ebaid (2001) found that increasing irrigation intervals to 6 and 9 days from 3 days decreased the amount of water used.This indicated that highest saving of irrigation water was found when irrigation intervals increased from 3 days interval to irrigation every 9 days while, water productivity (IWP) was maximum when irrigation interval increased to 6 days.This conforms to Dahmardeh et al. (2015) who reported that reduction in irrigation water increased water productivity.Higher IWUE was achieved under interval irrigation with 7 days intervals over 3 days as reported by Hameed et al. (2013).
The interaction effect of irrigation frequencies and tillage practice on irrigation water productivity (IWP) was found to be significantly higher with the treatments combination involving 6 days irrigation interval.This shows that irrigation has more influence on the water productivity than the tillage practices.The increased in irrigation interval from the commonly practice (3 days irrigation interval) to 9 days has saved more irrigation water (37.50 and 36.36%)but this resulted in highest reduction in yield (36.39 and 36.98%) in both seasons respectively.The least reduction in yield of 5.39 and 6.09% were recorded with 6 days irrigation interval respectively in both years and saved 28.84 and 27.52% irrigation water respectively (Table 5).The water saved was higher than the studies of Tantawi and Ghanem (2001) who reported 16.7% water saved for 6 days irrigation interval for rice and a yield reduction of 4.2% and conforms to Hameed et al. (2003) observations that with longer intervals (7-days) the yield was reduced by about 6% on average, but water consumption was reduced by more than one third.That means reduction in yield in respect of water saved in 6 days irrigation interval which has the highest IWP is more economical and a better irrigation schedule for rice in the ecological zone.

Conclusion
Higher paddy, straw yield and harvest index were higher with 3 days irrigation interval but were placed in group with 6 days interval.In general higher irrigation water productivity and the least reduction in yield were recorded with 6 days irrigation intervals.Therefore 6 days interval irrigation is recommended and with this total rice production can be increased by using water saved to irrigate more paddy fields.

Table 4 : Interaction Effects of Different Irrigation Frequencies and Tillage Practices on Irrigation Water Productivity of Rice in 2012 and 2013 Seasons
Irrigation Water Productivity of Rice under Various Irrigation Schedules and Tillage Practices in Northern Guinea Savanna Region of Nigeria I0 = 3 Days irrigation, I1= 6 Days irrigation, I2 = 9 Days irrigation, T0= Zero tillage, 114 Freedom Timon et al.