Response of Sorghum (Sorghum Bicolor L. Moench) To Potassium, Zinc, and Boron Fertilizers in Wag-Lasta, Northern, Ethiopia

In Ethiopia using fertilizer started in the early 1960. But it still depended solely on urea and DAP. Today, according to ATA and Ministry of Agriculture and Natural Resources K, Zn, B, S, and Cu are in decit in Ethiopia and Amhara Region as well as in Wag-Lasta areas. But some studies conducted in Wag-Lasta and throughout the region in different crops indicate that these nutrients had no response on crop yields. So, this experiment was conducted in 2017 rain feed cropping season on ve farmers’ parcels per location to verify the response of sorghum to potassium, zinc, and boron fertilizers.


Conclusions
Therefore, currently to increase production and productivity of crops in Wag-Lasta areas using of recommended rate of nitrogen and phosphorous with organic fertilizer sources for each district is the best option rather than using K, Zn, and B fertilizers.

Background
Agriculture is the master king of Ethiopia's economy, accounting for 34% of GDP and 85% of employment (Baye, 2017). However, the sector is not effective due to low soil fertility and inappropriate nutrient management practice. Sorghum (Sorghum bicolor (L.) Moench) is a viable food grain for many of the World's most food-insecure people who live in marginal areas with poor and erratic rains and poor soils (Onyango et al., 1998). In Ethiopia, sorghum is a major staple food crop, ranking second after maize in total production. It ranks third after wheat and maize in productivity per hectare, and after teff and maize in area cultivated. It is grown in almost all regions of Ethiopia, In Sekota and Lasta districts the crop is dominant. Sorghum production and productivity have been far below the potential. Currently, the average regional productivity is 2448 kg ha −1 , but, in the Waghimera zone, it was 1520 kg ha −1 , (CSA, 2017). The reasons were poor soil fertility, moisture stress, and inappropriate inorganic fertilizer rate (Amelework et al., 2016;Sebnie and Mengesha, 2018).
In Ethiopia, fertilizer use had been started since the early 1960s (Murphy, 1968). In the past three decades, Ethiopian agriculture depended solely on imported fertilizer products of urea and di-ammonium phosphate (DAP), sources of N and P. Today, according to the Agricultural Transformation Agency (ATA) and ministry of agriculture and natural resources (2016), soil fertility inventory conducted in some woredas of the country and the region from 2012-13 not only N, and P but also K, S, B, Cu, and Zn de ciencies are widespread. The fertility map of Wag-Lasta indicates that nearly 80% NPSZnB, 47% NPSB, and 98% K were de cit in the area. But the result of diagnostic nutrient omission trial conducted in Potassium, zinc, and boron nutrients are required and indispensable for crop optimum growth, development, and production (Hasanuzzaman et al., 2018), however, in Wag-Lasta these nutrients had no signi cant effect on crop yield due to the areas' soil had a high amount of exchangeable potassium amount. But the extension agent widely distributes NPSB, SPSZnB fertilizers to the farmers, which expose users to extra cost. Therefore, the study was conducted to verify the response of sorghum to potassium, zinc, and boron fertilizers application and to validate the soil fertility map developed by the Ethiopian soil information system (EthioSIS).

Experimental design and treatments
The treatments were NPS, NPSK, NPSZnB, and NPSZnBK. N and P fertilizers amount adjusted by the recommendation rate of 46 and 23 kg ha −1 N and P 2 O 5 for Sekota respectively, and 23 kg ha −1 for both N and P 2 O 5 for Lasta district, murite potash applied by blanket recommendation of 150 kg ha −1 KCl, Zn, and B uniformly applied 0.7 and 1.47 kg ha −1 for all trial sites respectively. NPS, NPSZnB, and murite potash fertilizer were added at planting time while urea was added in split application half at planting and the remains half after 30 -45 days planting at knee height. The experiment was laid out in randomized complete block design (RCBD) with three replications. The plot size was 18.75m 2 (3.75 m X 5 m) and consisted of 5 rows. 1m distance was left for both between plots and blocks. Spacing of 75 and 15 cm was used between rows and plants respectively. The tested variety was Misker. All recommended agronomic crop managements were done for all treatments uniformly at their own appropriate time.

Data collection
The average plant height taking representative ten samples from each plot randomly and measured by tape meter from ground to tip of the head, length of sorghum head, grain yield was collected from central rows, while excluding border rows from each plot separately.

Data analysis
The data obtained from this research were subjected to analysis of variance using SAS software version 9.0 (SAS, 2003) and treatment effects were compared using the Fisher's Least Signi cant Differences test at a 5% signi cance level. Soil reaction (pH) was measured from ltered suspension of 1:2.5 soil to water ratio using a glass electrode attached to a digital pH meter. Soil organic carbon was determined following the wet digestion method as described by Walkley and Black (1934 . Sulfur is also determined by the Turbidity method and soil texture was determined by the bouyoucos hydrometer method (Bouyoucos, 1962;Beverwijk, 1967).

Result And Discussion
Soil analysis result at planting The soil analysis data was important to identify the level of nutrients in the soil and to determine suitable rates and types of fertilizer for the recommendation. The average soil pH of the trial sites was 5.92, according to Tadesse (1991) it was moderately acidic. Based on the results of soil analysis as shown above in Tablec1, the average total nitrogen (%TN) ranges from 0.02-0.05, based on Tadesse (1991) it was categorized under very low and low. Besides, the available phosphorus (Av. P) was ranged from 4.79-23.24 PPM, based on Cottenie (1980); which grouped under very low, low, medium, and high class. Moreover, soil organic carbon (%OC) of the trial site was ranging from 0.37 -0.8, as Tadesse (1991), it was very low and low, so improving soil organic amount needs immediate actions through applying organic fertilizers sources like organic manure, compost, crop residue retention, and crop rotation (Tulema, 2005; Araya, 2010). Soil textural class was also sandy loam, sandy clay loam, and loamy sand both of them were good for crop production activities but due to its high capacity of in ltration rate, it couldn't store water for a long time in dryland areas. The exchangeable potassium of the trial site ranged from 0.84-1.35, according to FAO, (2006) it is very high and high.

Grain yield
The application of K, Zn, and B fertilizers did not signi cantly affect grain yield in Sekota and Lasta districts (Tables 3 and 5). The highest grain yield was obtained from the application of NPS fertilizer in most experimental elds. Whereas the lowest yield was recorded from K, Zn, and B combined with NPS. This might be due to the overdose applications of these nutrients. This nding positively correlated with soil analysis data of experimental elds as illustrated above in Table1 (Anjum, 2017;Nadim et al., 2012), examined that Foliar application of 1% Zn and 0.5% B had to pronounce results on maize yield and boron 2 kg ha −1 recorded more grains spike −1 , higher grain weight, and increased grain yield of wheat.

Conclusion And Recommendations
Application of K Zn and B fertilizers had an insigni cant effect on plant height, head length, and grain yield of sorghum, in Sekota and Lasta districts. In most trial sites yields obtained from NPS fertilizer are better than NPSK NPSZnB and NPSZnBK, as a result, these fertilizers had no yield advantage in the districts because the districts' soil has a su cient amount of exchangeable potassium for optimum crop production. Soil fertility maps of Sekota and Lasta district are unrelated to the current soil status of potassium zinc and boron nutrient content. Currently to increase production and productivity of sorghum in Wag-Lasta areas using of recommended rate of nitrogen and phosphorous with organic fertilizer sources for each district is the best option rather than using K Zn and B fertilizers, and the effect of K Zn Cu B and other essential nutrients should be checked as they will be expected de cit from the soil in the long run. Figure 1 Soil fertility map of Sekota district developed by ATA Figure 2 Soil fertility map of Lasta district developed by ATA.