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 infiltration 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.
Table 2
Effect of K, Zn, and B fertilizers on PH and HL of sorghum in Sekota district
| Fikreselam | | Rubariya | | Tiya | | Woleh | |
Trts. | PH.cm | HL.cm | PH.cm | HL.cm | PH.cm | HL.cm | PH.cm | HL.cm |
NPS | 157.97 | 18.56 | 164.07 | 18.4 | 134.65 | 17.33 | 147.8 | 21.07 |
NPSK | 152.17 | 17.88 | 160.07 | 18.46 | 142.05 | 16.81 | 155.48 | 19.87 |
NPSZnB | 158.22 | 18.24 | 166.17 | 20.4 | 141.2 | 17.46 | 150.4 | 21 |
NPSZnBK | 149.12 | 18.46 | 156.27 | 17.92 | 138.18 | 17.13 | 158.12 | 19.51 |
LSD 5% | NS | NS | NS | NS | NS | NS | NS | NS |
CV | 2.62 | 2.48 | 3.1 | 4.02 | 2.84 | 1.48 | 7.8 | 5.6 |
Where: Trts presents treatment, PH refers plant height, HL stands for head length, NS represents non significant |
Table 3
Effect of K, Zn, and B fertilizers on grain yield of sorghum in Sekota district
| Fikreselam | Rubriya | Tiya | Woleh |
Trts | GY Kg ha−1 | GY Kg ha−1 | GY Kg ha−1 | GY Kg ha−1 |
NPS | 1480 | 2670 | 1420 | 3230 |
NPSK | 1370 | 2560 | 1570 | 3070 |
NPSZnB | 1240 | 2610 | 1460 | 2910 |
NPSZnBK | 1230 | 2400 | 1450 | 3100 |
LSD 5% | NS | NS | NS | Ns |
CV | 5.87 | 4.5 | 4.01 | 4.8 |
Where: GY refers to grain yield |
Table 4
Effect of K, Zn, and B fertilizers on PH and the HL of sorghum in Lasta district.
| Genet Mariam | Qechn abeba 1 | Qechn abeba2 | Shumsha |
| PH.cm | HL.cm | PH.cm | HL.cm | PH.cm | HL.cm | PH.cm | HL.cm |
NPS | 159.39a | 18.83 | 140.47 | 18.82 | 131.1 | 17.4 | 158.4 | 21.26 |
NPSK | 146.27b | 17.93 | 146.47 | 20.16 | 131.3 | 16.16 | 171.31 | 22.53 |
NPSZnB | 146.47b | 17.33 | 143.27 | 17.36 | 126.36 | 17.4 | 164.91 | 22.26 |
NPSZnBK | 147.53b | 17 43 | 145.87 | 18.9 | 132.84 | 17.2 | 149.96 | 18.58 |
LSD 5% | 7.4 | NS | NS | NS | NS | NS | 16.05 | NS |
CV | 6.9 | 3.68 | 2.6 | 4.4 | 2.31 | 2.82 | 2.75 | 9.1 |
Table 5
Effect of K, Zn, and B fertilizers on grain yield of sorghum at Lasta district
Trts. | Genet Mariyam | Qechn abeba1 | Qechn abeba2 | Shumsha |
| GY kg ha−1 | GY kg ha−1 | GY kg ha−1 | GYkg ha−1 |
NPS | 1710a | 1080 | 1200 | 3300 |
NPSK | 1040b | 1240 | 860 | 4010 |
NPSZnB | 940b | 910 | 940 | 2860 |
NPSZnBK | 1406a | 1140 | 1090 | 3160 |
LSD 5% | 0.3 | NS | NS | NS |
CV | 8.4 | 11.75 | 14.16 | 8.43 |
Plant Height And Head Length
Potassium, zinc, and boron fertilizers had no significant effects, among and between treatments on plant height and head length of sorghum in Sekota and Lasta districts at (p ≤ 0.05) Table 2 and 4. Thus the resulting matched with soil analysis results as mentioned in Table 1. When the available K in the soil was deficient or not supplied adequately, the growth would be stunted. But the amount of readily available (exchangeable) potassium in the soil to provide the crop was high. This result was in line with (Amare et al., 2018; Hasanuzzaman et al., 2018). Furthermore, zinc and boron have a great role in plant growth and development. However, in the case of these experimental fields, it had no significant effect on plant height and head length. It might be due to the soil full filling the required amount of Zn, and B for sorghum. This result agreed with (Ayalew and Beyene, 2011; Amare et al., 2018; Kassie et al., 2019; G.Selassie et al., 2020) who reported that K fertilizer application had no significant effect on crop growth parameters of sorghum, maize, wheat, potato and tef in northwestern, southern, and northeastern, Ethiopia. Though, it was contradicted with (Markos et al., 2015; Berhe, 2017; Tesfaye et al., 2021) who reported that K had a response on maize and wheat agronomic parameters. Similarly, it disagreed with (Pholsen and Somsungnoen, 2004; Bayu et al., 2006) who reported that boron and potassium fertilizers had a significant effect on sorghum height.
Grain yield
The application of K, Zn, and B fertilizers did not significantly 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 fields. 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 finding positively correlated with soil analysis data of experimental fields as illustrated above in Table1. Although the overall yield except for Shumsha, Rubariya, and Woleh sites was low due to low soil fertility status and moisture deficit problems. But the yield was equal with (CSA, 2017; Assefa et al., 2020) results. Shumsha and Rubariya sites yield similar to Sebnie and Mengesha (2018) who found 3822 and 2959 kg ha−1 by using 23 kg N ha−1 and P2O5 for Shumsha, and 46 and 23 kg N ha−1 and P2O5 for Rubaria. There were yield variations among sites due to soil fertility variation.
K, Zn, and B has a role in growth, development, yield increment, diseases resistance, formation of different enzymes for crops (Brady and Weil, 2002), but in the wag-Lasta areas it had no yield advantage on sorghum, rather than the recommended rate of nitrogen and phosphorous fertilizers. This might be due to the soil having enough (high) amount of exchangeable potassium, the current result of this research was agreed to the diagnostic nutrient omission trial result of (SDARC, unpublished; Amare et al., 2010; Amare et al., 2018). Similarly, the current finding in line with Wag-Lasta areas results using 72 kg K2O, ha−1 had no significant effect on teff and wheat yield. Also, this finding is in line with G.selassie et al. (2007), who investigated potato tuber yield had no response for K fertilizer application in western Amhara Region, Ethiopia. Similarly, it was agreed with (Kassie et al., 2019) who reported that the application of 150 kg KCl ha−1 had no yield increment advantage on sorghum, bread wheat, and food barley crops in the north Shewa zone of Amhara region, Ethiopia. Simultaneously, (Ayalew and Beyene, 2011) reported that adding different rate levels of K fertilizer had no potato tuber yield increment in southern Ethiopia.
The finding of this research contradicted with soil fertility map of the Sekota and Lasta districts. The maps were developed by ATA and the ministry of Agriculture and Natural Resources (2016). It showed more than 98% of potassium deficiency and more than 80% NPSZnB deficiency. But, this study proves that K Zn and B nutrients are not a deficit in Wag-Lasta districts, rather they are inadequate amount to provide for crop optimum growth, development, and yield in the areas as shown in table 1. This study result was contrasting with Tilahun et al. (2015), who reported that Zn is optimal and B below the critical level in Alicho-Woriro, woreda, Siltie zone, Southern Ethiopia. Simultaneously, it was disagreed with (Berhe, 2017; Tesfaye et al., 2021) reported K fertilizer had a yield advantage on wheat in southern, Ethiopia. However, this finding disagreed with (Gebrekorkos et al., 2017; Redai et al., 2018), who reported that NPKSZn, NPK, and NPSZn had yield advantage by melkam variety of sorghum than NP fertilizer in Tigray Region, Ethiopia, and Bekele (2018) who found using 120 kg ha−1 K2O increases onion yield in Jimma, Southwestern Ethiopia. Similarly, (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.