Iris Publishers - World Journal of Agriculture and Soil Science (WJASS)

Growth, Yield and Yield Components Response of Local Sorghum Varieties to Nitrogenous Fertilizer Rates in Northern Ghana

Authored by Joseph Xorse Kugbe

The economic importance of Sorghum (sorghum bicolor L. Moench) to rural households and household food security in northern Ghana, remains a key reason for the continues cultivation of the crop, though average yield (700 kg/ha) is below that of maize and rice. The low yield, however, implies that sorghum could contribute more to food supplies than at present, especially in resource-constrained regions and people in greatest need. The crop has been referred to as one with vast untapped potential [1,2].

Across northern Ghana the crop is preferred by farmers because of the relatively dry agricultural environment. Sorghum is an extremely drought tolerant crop and has an ability to survive and yield grain during continuous or intermittent drought stress [3]. As a result, the crop has been and is still an important staple in most Semi-Arid Tropics (SAT) of Asia and Africa [4]. In Africa, sorghum has wider geographical adaptation than any other cereal growing from lowlands to highlands [5].

Though adapted to the arid climates of northern Ghana, productivity is by far below its potential. In areas where sorghum is commonly grown, yields of more than 3000 to 4000 kg ha-1 are obtained under better conditions, dropping down to 300 to 1000 kg ha-1 as moisture, soil fertility and other biotic and abiotic factors become limiting [6].

In northern Ghana, sorghum is cultivated principally by smallholder, resource-poor farmers under rain-fed conditions. Mostly, fertilizers are not available for purchases. In some cases where fertilizers are available the farmers have no means to purchase them or lack access to fertilizer through lack of transportation to cart fertilizers to the field. Judicious use of fertilizers is paramount to sorghum production.

Despite being one of the most important staple food for many livelihoods and its adaptation to draught, research results reveal that yield levels achieved by small-scale farmers remained stagnant despite farmer’s effort to improve and increase production. Across northern Ghana, poor soils and lack of knowledge on fertilizer application rates remain key factors to the reduced yield. Though a number of local varieties have been introduced to increase the yield of the crop, knowledge on best performing sorghum variety is also limited.

In order to increase sorghum production, there is a need therefore to evaluate the effect of N fertilizer rates on local sorghum varieties to determine the optimum N rate and variety. Appropriate N fertilization rates have been noted to increase sorghum yields. Olugbemi et al. [7], observed that application of N up to 150 kg/ha increased grain number, grain yield, and harvest index. It has also been observed by Melaku et al. (2018), that sorghum varieties has responded differently to N application rates and that sweet sorghum varieties gives higher grain yield, biomass, plant height, leaf number and quality stalks due to its ability to respond effectively to increasing N application rates. In 2018 an evaluation research was conducted by Al-salim et al. [8] on local sorghum (keafer, Al-khyaer, Rabeh and Enqadh) genotypes to evaluate their response to nitrogen fertilizer application rates and it was established that the local sorghum genotypes respond well to nitrogen fertilizer rates. Sorghum genotypes have been reported to be good efficient responders or users of N fertilizer levels [9,10]. Across northern Ghana, however, knowledge on varietal response to N fertilization is limited. Necessitating the need for a research to develop knowledge to help improve the crops production. This research was aimed to assess the effect of N fertilizer rates on growth, yield and yield parameters of local sorghum varieties in northern Ghana with the objective to help identify the best local sorghum variety that responds effectively to the most economic N fertilizer rate for resource-poor farmers of northern Ghana.

Materials and Methods

Description of the study area

The experiment was conducted at Vea during the 2014 and the 2017 cropping seasons.

The area lies within the interior Guinea Savannah agro-ecological zone of Ghana, located in the Bolgatanga municipality of the upper east region between latitude 90ʺ 25 N, longitude 00ʺ 58W. The climatic condition of the area is warm, semiarid with an annual average rainfall of 1200 mm between May and September, followed by a dry windy season (harmattan) from September to April. Temperature distribution is moderately uniform with mean monthly minimum value of 31°C and maximum of 38 °C [11]. The relative humidity varies greatly during the wet season with monthly minimum of 25% and maximum value of 50% during the wet season [12]. The soil types include Lixisols, and Ferric Lixisols [13].

Growth parameters:

• Variety name: Varieties of local sorghum used for the field experiment were named and recorded.

• Fresh weight of biomass (FWOB): Data recording started a month after emergence and was taken every two weeks.

• Dry weight of biomass (DWOB): Data recording started a month after emergence and was taken every two weeks interval.

• Leaf number: This was recorded a week after emergence and continued every two weeks till the flag leaf stage. This was determined by counting. Five plants that were sampled randomly and tag from the middle rows of each plot were used for this purpose.

• Plant height (cm): Plant height of sorghum was measured every two weeks from a week after emergence in centimeters. It was measured as the distances from ground level to the growth point where the panicle starts to branch. Five plants were sampled randomly from each plot in the middle rows and used for this purpose. The mean was recorded as plant height.

Yield and yield components

• Final total biomass (above ground biomass): This was recorded at the time when the sorghum plants were fully matured and ready for harvest. The plants were cut from the net rows and weighed from each net plot. The weighed biomass was then converted to kg/ha.

• Panicle weight: This was determined by randomly selecting five panicles and weighing the panicle with grain attached. Panicle weight was then recorded by dividing the total weight by the number of panicles.

• Panicle length and width: This was determined by selecting five panicles and measuring the panicle length and width of the panicle with grain attached.

• Number of spikelet’s and florets: This was determined by selecting five panicles and counting the number of spikelet’s and florets in the panicle.

• Two hundred seeds weight: This was determined by selecting five panicles randomly. Two hundred (200) seeds from these panicles were carefully counted after which the weight of the 200 seeds was recorded.

• Grain Yield: Grain yield was measured by weighing the grain that was threshed from the panicles obtained from the harvest area within each plot and expressed into kg/ha.

Data analysis

The data collected were subjected to analysis of variance (ANOVA) using the GenStat statistical software. The differences between treatment means were compared using Least Significant Difference (LSD) test at 5% level of significance.

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