The Response Of Amaranth us cruentus L.:

Abstract

Prince's feather Amaranthus cruentus, a staple leafy vegetable grown in the humid region of sub-SaharanAfrica is widely known for its nutritional and medicinal importance. Its cultivation is however mostly limited to the wet seasons of the year. This is largely due to: inadequate water supply and rapid depletion of moisture from soil during dry seasons, and lack of reliable and relevant data on crop water requirement at the different stages of development and their relationship to yield. Dearth of knowledge about appropriate use of modern irrigation systems has also hindered successes that would have been made at improving Amaranth production during off seasons. Dry season farmers (mostly Fadama farmers) often use intuition and other non-scientific methods to apply water to crop and this often leads to under-irrigation or over-irrigation of crops. Therefore, this study was aimed at determining the response of Amaranthus cruentus to different water application levels using sprinkler and drip irrigation systems and as well determine the water-yield relationship for the crop with a view to proposing the most effective irrigation method for its optimum yield under a controlled moisture supply in the study area. A two (2) year field experiment was carried out to investigate the growth, yield and water use pattern of Amaranthus cruentus under limited water supply. The experiment was carried out at the Research and training Farm site of the Department of Agricultural Engineering, Federal university of Technology, Akure. A preliminary investigation was carried out on the soil physical and chemical characteristics, climate variations and water resource of the study site to determine its potentials for dry season farming. A 2 x 3 x 3 combination of two irrigation methods (Drip and sprinkler systems), three (3) crop phenological stages (Emergence, vegetative/fruiting, maturity) and three water stress levels (50-59,60-69 and 70 KPa). The treatments were twice replicated using a randomized complete block design (RCBD). Measurements taken on the field during experiment include soil moisture content using the gravimetric method, soil bulk density, the soil hydraulic change using mercury tensiometers, overland flow during occasional rainfalls in the field by use of developed and celebrated runoff meter, deep drainage from the field using hydraulic lysimeter. Measured crop parameters include the plant height, the leaf area and leaf area index (LAI), the number of leaves and Amaranthus cruentus yield. Weather variables such as solar radiation, minimum and maximum relative humidity, minimum and maximum temperature and wind speed from the field were measured with the aid of automatic mini-meteorological station installed some 200m away from the site of experiment. Soil, crop and meteorological data collected were subjected to statistical analysis such as Analysis of variance (ANOV A), mean, standard deviation and linear and multiple regression analysis. Results obtained from the experiment showed that the soil hydraulic charge (9) is higher during the dry season experiment of 2005 than 2006. Soil moisture depletion during the wet season experiment was close to zero most times at the different soil depths; hence no irrigation was necessary during the wet season experiment. Also, the variations in volumetric moisture content showed an increase in moisture regime down the soil profile. Moisture was readily available for crop use in the treatments that was well watered (STI and DTI). However, as crop reaches maturity and senescence, soil moisture storage for all treatments is reduced due to reduction in canopy at full crop maturity. Consumptive use of crop (Evapotranspiration) was highest (9.96 mm/day) in drip plots DTl and DT2 at the peak of the dry season (57-64 DOY). Reduced radiation at the onset of raining season brought about reduced evapotranspiration to as low as 0.30 mm1day. The value of crop factor k, for Amaranthus cruentus on function of day of the year reduced marginally at the earlier stage of crop growth but rose sharply during the productive stage of the crop. At late season during crop senescence, crop factor kc maintained nearly constant values. The coefficient of correlation between crop consumptive use and the growth stage of Amaranthus (emergence to maturity) was highest (0.94) in sprinkler plot ST6. Crop yield model based on equation calibrated on Amaranthus cruentus yield showed good agreement with the field data. The correlation coefficient (R) of the model output and the measured yield was significantly high (0.86). Linear regression analysis carried out on yield on function of cumulative moisture stored at the vegetative stage of the crop showed that the coefficient of determination between crop yield and soil moisture stored was higher (R=O.84) on drip plots than on sprinkler plots (R=0.74) at P<0.05. Simulated crop growth and soil water balance showed a significantly high agreement with field determined growth and actual evapotranspiration of Amaranthus cruenthus. The WaSim model simulated crop growth and crop cover adequately well, the coefficient of determination (R2 = 9.9) is high. Findings from this research are useful for careful planning of irrigation to meet crop water demand during off seasons most especially in areas of limited rainfall occurrences.