Identification of Yield-Limiting Nutrients for Sorghum ( Sorghum bicolor (L.) Moench) Yield, Nutrient Uptake and Use Efficiency on Vertisols of Raya Kobo District, Northeastern Ethiopia

. Agricultural productivity was negatively impacted by low soil fertility and uneven fertilizer application during crop cultivation in Ethiopia. Because of this, important crops frequently respond to fertilizer applications signifcantly below their achievable and potential yields. Tis study was carried out to determine the most sorghum yield-limiting nutrients in the Raya Kobo area of the Amhara Region in the 2020/21 crop season. Sorghum variety Girana-One was used as the test crop. Control, NPS, PSBZn, NPBZn, NSBZn, NPSB, NPSZn, NPSBZn, recommended NP, and NPSKBZn were treatments. Tree replications of the experiment were used in a randomized complete block design. Before treatment application, a composite soil sample was collected at a depth of 0–20 cm to determine the soil’s physicochemical properties. To evaluate N and P uptakes, samples of sorghum stalk and grain were collected. SAS software was used to analyze the data. Results showed that, NPKSZnB produced a considerably greater grain yield (4620 kg · ha − 1 ), whereas the control and N omitted plots produced the lowest grain yields (2759 kg · ha − 1 ) and 2805kg · ha − 1 , respectively. Nitrogen fertilizer missing plots showed a statistically signifcant yield drop compared to the other plots, and there was no statistically signifcant yield diference between the prescribed NP plots and the potassium, sulfur, boron, or zinc omitted plots. Te plots treated with NPKSZnB had the highest agronomic efciency for N (19.7 kg grain kg − 1 · N) and P (10.6kg grain kg − 1 P 2 O 5 ). Terefore, research and development should therefore concentrate on nitrogen to achieve the best sorghum yield for the study location. Phosphorus might also be used to keep the fertility level within the ideal range.


Introduction
1.1.Background and Justifcation.Depletion of soil fertility is among the key barriers to agricultural growth in Ethiopia.As a result of high erosion rates, the removal of biomass and animal manure from farmland, and the limited application of inorganic and organic fertilizers nutrient diminution rates are aggravated in the country like many East African countries [1].In addition, abandoning the traditional practices with natural fallow or uncultivated systems to repair soil fertility and inadequate supply of nutrients are the key constraints and challenges to crop production faced by smallholder growers in Ethiopia [2].Tis shows that interventions targeting soil fertility evaluation must be designed to improve the success of crop productivity.
Fertilizers have a signifcant role in raising crop output, and the careful application of mineral fertilizers is credited with a signifcant portion of the rise in global food production [3].In Ethiopia, fertilizer recommendations are based on extremely generic standards for each type of crop, or more frequently, a single recommendation for all crops, which is 100 kg DAP and 100 kg urea [4].Ignorance of nutrients other than N and P may reduce crop productivity.
Unbalanced fertilizer use during crop cultivation will deplete soil nutrients, resulting in a drop in crop productivity and deterioration of soil nutrients [8].To maintain agricultural productivity, it is crucial to apply the right amount of balanced fertilizer to maintain the soil's nutrients.An omission trial shows the crop's response to nutrient availability in a visible order [9].Estimates of the crop's capacity to deliver nutrients based on its need as per the target yield from the omission trial revealed an improvement in yields [10].
Productivity is increased with the help of advice for the right fertilizer applications depending on the local climate, soil, and management techniques.However, the need for additional nutrients varies greatly between felds, seasons, and years [11].In general, fertilizer doses cannot be applied to all crops and felds.Terefore, to boost the productivity of sorghum, it is necessary to quantify the nutrient supply of soils for macronutrients such as nitrogen (N), phosphorus (P), potassium (K), and sulfur (S), as well as micronutrients such as zinc (Zn) and boron (B), and the response of crops to these nutrients.Terefore, it is necessary to determine the nutrients that are most likely to limit yield in the vertisols type of soil in the Raya Kobo district to boost sorghum yield.

Description of the Study Area.
Te trial was conducted on the vertisols type of soil, of the Raya Kobo district, located at 12 °09′N latitude and 39 °38′E longitude and has a 1468 masl elevation (Figure 1).
Te principal feature of rainfall (RF) in the district is bimodal, with two distinct rainfall seasons.Based on the data from Kobo meteorological station during the last twenty years (2001-2020) (Figure 2) rainfall pattern is characterized by seasonal, poor distribution, and erratic.

Experimental Materials.
Te experiment was carried out over the key crop seasons of 2020/21 on the farmers' land at Raya-Kobo district.High yielding and early maturing sorghum variety (Girana-One) was used as a test crop.

Experimental Design and Treatments.
Te experiment consists of ten treatments, as described in Tables 1 and 2 and organized in a randomized complete block design (RCBD) with three replications.Te spacing among plots and replication was 1 m.Planting was made at the onset of the short rain in mid-July 2020 in a row by drilling.Te gross sizes of the plots were 4.5 m × 3 m (13.5 m 2 ) in six rows per plot.Te spacing between plants was 15 cm, and the distance between rows was 75 cm.Two weeks after germination and emergence, one seedling per hill was thinned out.

Nutrient Source and Application Method.
Phosphorus, potassium, boron, sulfur, and zinc were applied at planting as triple super phosphate (TSP), potassium chloride (KCl), borax, calcium sulfate, and zinc oxide, respectively.For all N containing treatments half of N contain fertilizer (Urea) was applied at planting and the remaining half of N fertilizers were applied at 45 days after planting just after weeding with the presence of small rainfall.All recommended practices were done during the development period of sorghum.Beginning in the frst week of November and continuing until mid-November, harvesting and threshing took place.

Collection of Soil Samples and Analyzes.
After clearing the soil surface of any debris and plant litter, soil samples were collected from representative experimental plots before planting.Using a soil auger, soil samples were taken in a zigzag pattern from 0 to 20 cm deep.Each soil sample taken from the test plots was bulked to create a single composite soil sample weighing one kilogram.To evaluate the soil bulk density, additional undisturbed soil core samples with known volumes were taken from all plots.
Te bulk density of the soil was calculated after drying of the soil sample at 105 °C in an oven until a constant weight was recorded [12] and calculated as follows: where ρb � bulk density; Ms � mass of solid (oven dry weight of soil); Vt � volume of total soil sample.Potentiometric analysis was used to determine the pH of the soils in water suspension at a ratio of 1 : 2.5 (soil to liquid) [13].Te micro-Kjeldahl digestion method was used to calculate total nitrogen (TN) [14].Olsen et al. [15] was used for the determination of available P from the soil sample.Using the wet digestion method, the soil's organic carbon content was examined [16].Titrimetrically, CEC was determined by distilling the ammonia that sodium replaced [17].Ajwa and Tabatabai [18] used the FAO-turbidimetric approach to analyze the available S and a fame photometer to assess the exchangeable K + .Diethylene triamine pentaacetic acid (DTPA) extraction was used to quantify zinc using the method created by Lindsay and Norvell and described by Sertus and Bekelye [19].Berger and Truog [20] method of hot water extraction of soil was used to determine the amount of available boron.

Data Collection and Measurements on Yield and Yield
Components.Soil plant analysis development (SPAD) value, plant height, above ground biomass, and Grain yield were collected as follow: 2 International Journal of Agronomy SPAD value: SPAD-502 chlorophyll portable meter (Minolta, Osaka, Japan) was used to measure the SPAD value of sorghum by taking fully developed leaves, and then three places were selected from fve plants to take the average from a stage of fower initiation.All chlorophyll meter readings were taken midway between the stalk and the tip of the leaf.Plant height: Te height of the plants was measured at harvest from the base of the plant to the top.Average values of randomly selected plants were measured and expressed as mean plant height in centimeters.Above ground biomass: It was measured by taking the weight of the above ground biomass of plants in a plot at maturity and converting it to kg per hectare.It was adjusted by drying a sample of plants until a constant weight is attained with oven (at 105 °C).Grain yield: It was measured by taking the weight of the grains for plants in a plot at harvest and converting it to kg per hectare after adjusting the grain to 12.5% moisture content.

Grain and Stalk Sampling Analyzes.
Te above ground parts of sorghum were cut at ground level at the harvesting stage, and representative stands were taken in each central plot randomly for both grain and stalk nutrient content analysis.Te stalk and grain samples were analyzed for nutrient for total N and P from each plot separately.Te wet-oxidation procedure of the Kjeldahl methods and dry ashing method were used for N and P content determination.

Estimation of Total N and P Uptake. Nitrogen uptake:
It was calculated by multiplying the respective stalk and grain yields by the N concentration.Te N and P uptake of the grain and the stalk were added to determine the total N and P uptake.International Journal of Agronomy Te following empirical formula was used for nutrient uptake determination: as stated by Weldegebriel et al. [21].

Nutrient uptake by Grain or Stalk
where GY is grain yield and SY is stalk yield.

Nutrient Use Efciency.
Te yield increase per applied unit of nutrient is used to calculate agronomic efciency (AE).Agronomic use efciencies of N or P fertilizer nutrient (AEN) are calculated using the procedure designated by Dobermann [22] as cited by [23] AE kg grain kg nutrient where F is fertilized treatment; and io is the treatment i nutrient omitted.

Statistical Analysis.
To fnd diferences across treatments, the collected data on yield, yield metrics, and nutrient uptake and use efciency were subjected to an ANOVA analysis using SAS software (version 9.3).Te Duncan Multiple Range Test (DMRT) was used to distinguish between signifcant treatments means, with a 5% level of signifcance.Te Gomez and Gomez [24] method was used to calculate the correlation between the parameters in order to determine the association between yield and yield components.

Initial Soil Property of the Trial Site
3.1.1.Selected Physical Properties of the Soil.Te result of the soil particle size distribution analysis of the study site (Table 3) indicated that the soil has 47.5% clay, 25% sand, and 27.5% silt fractions, which are categorized under the clay textural class [25].Tis textural class is one of the most important soil characteristics and has a signifcant efect on crop production [26].High water holding capacity is the characteristics of such type of soil.Te average bulk density was 1.26 g/cm 3 which are relatively low.Tis implies that the soil is good for plant growth and seed germination [27].For 4 International Journal of Agronomy International Journal of Agronomy clay soils, 1.4 g•cm −3 is the threshold value of bulk for plant growth at which root penetration is expected to be severely constrained [28].Following this critical value for clay texture, the stated bulk density value of the trial site is in the favorable soil textural class.

Selected Soil Chemical Properties.
Te experimental site's soil response (pH) was 6.3 (Table 3).Based on Tadese [29], the soil was slightly acidic.According to Hamza [30], the pH range of 5.5 to 7.0 appears to be ideal for enhancing plant nutrient availability.In addition, according to Horneck et al. [31] micronutrient defciencies rarely occur when the soil pH is below 6.5.According to Tadese [29] rating, the total nitrogen content was rated as low (0.09%).Tus, to replenish the leftover nitrogen that the soil was unable to provide to the crop in the study region, nitrogen-containing fertilizer must be applied.Te lower N content might be due to the continuous and intensive cultivation system in the district.Hamza [30] also reported that if organic matter is relatively low (1-2%), then there may not be enough nitrogen in the soil.Te SOM content of the experimental site was 1.96%, which can be considered medium/moderate as per the ratings of Tadese [29].Tis level of OM may be the result of ongoing agriculture without adding leftover material to the soil.Te OM content of Ethiopian vertisols was low [32].
According to Olsen et al. [15] rating, the experimental site's available phosphorus content was 11.8 ppm, which is categorized in the high range.Te exchangeable potassium for the experimental site was 1.2 cmol ( + ) kg −1 soil, which is classifed as very high according to FAO [33].Tus, the nutrient potassium is considered more than the adequate level in the study site and will not limit crop yield.
Te CEC of the experimental site was 17 cmol ( + ) kg −1 which is rated as medium based on Hazelton and Murphy [28] rating.According to those authors, a CEC value between 12 and 25 cmol ( + ) kg −1 is rated as a medium.Tis amount of CEC in soils of the trial area could be associated with moderate levels of clay and the OM content of the soil.Te analysis of the preplanting soil (pH, total N., avail.P, OM, and textural class) result (Table 3) is in line with the soil test outcomes of Getu et al. [34] and Bayu et al. [16] in the same district.
Te available sulfur content of the experimental site was 5.7 ppm.According to Horneck et al. [31] rating soils with 5-20 ppm content of sulfur are grouped as medium.Te DTPA extractable Zn content was 1.42 mg•kg −1 (Table 3).
Te greater levels of Zn in the soil than the average (0.9 mg•kg −1 ) was reported by Asgelil et al. [35].Te greater levels of Zn in vertisols type of soil in Ethiopia were also observed by Yifru and Mesfn.
According to FAO [36], the soil of the present experimental area was grouped as a medium, which is between 1 and 3 mg•kg −1 .According to Horneck et al. [31]; for most crops, a soil test with zinc levels above 1.5 ppm using the DTPA extraction method is sufcient.Te available boron recorded at the trial site was 0.77 ppm.Based on Horneck et al. [31], the availability of soil boron content of the present experimental site was categorized under moderate class.Te treatment of various fertilizers had a substantial (P ≤ 0.05) impact on SPAD value.Te SPAD reading was not signifcantly diferent in N containing plots, where the highest SPAD value (46.2) was recorded from S omitted plots while the lowest chlorophyll content (37.1) was obtained from unfertilized treatments (Table 4).N omitted plots had a signifcantly lower SPAD value than K, S, Zn, and both Zn and B omitted plots and from plots that received RNP and NPSKZnB.Increasing the SPAD value due to N would be associated with the higher nitrogen accumulation of sorghum leaves that ultimately donated to the synthesis of chlorophyll.According to this fnding, Ajeigbe et al. [37] indicated that the maximum SPAD value was discovered to be between 80 and 100 kg•N•ha −1 in the Nigerian BUK and Minjibir.Tose authors relate SPAD value with the nutrient supply capacity of the soil.Rostami et al. [38]; stated the SPAD measurements were signifcantly increased with N application in maize crop.

Plant Height.
Plant height varied signifcantly (P ≤ 0.05) between treatments.Te longest height of the plant (245.4 cm) was obtained from the application of NPS fertilizer, which showed a signifcant diference between nitrogen omitted and control (unfertilized) plots.Tese plots had the lowest plant height than the other N-containing treatments (Table 4).Tus the plant height reduction was observed in plots where nitrogen fertilizer was omitted.On average nitrogen omitted plots had a 15.9% height reduction as compared with NPS fertilized plots.Plant height in the plots of P, K, S, Zn, and B and both Zn and B omitted treatments were not signifcantly varied.Te highest plant height in all the treatments except in the N omitted and control plots was the result of the application of nitrogen.While the reduction in plant height under the control and N omitted plots might be associated with the defciency of nitrogen or inaccessibility of the nutrient to the plant.In line with these results, Gebrekorkos et al. [39] described that the application of fertilizer increases plant height of sorghum in Raya valley Ethiopia.In line with this result, Sebnie and Mengesha, [40] also stated that nitrogen and phosphorus fertilizers signifcantly afect the plant height of sorghum in the Wag-Lasta area of Ethiopia.In addition, Gebremariam and Assefa [41] also informed that the lowest and the maximum plant height of sorghum was attained from plots without nitrogen application and from 150 kg•ha −1 nitrogen, respectively.

Above Ground Biomass Yield. Te statistical analysis
showed that the application of diferent nutrients had a signifcant impact on the biomass yield of sorghum.Te lowest biomass yield (8892 kg•ha −1 and 9449 kg•ha −1 ) was attained from the unfertilized plots and N omitted plots, respectively (Table 5).Te omission of P, K, S, Zn, B, Zn, and B and the recommended NP didn't show a signifcant reduction in biomass yield of sorghum as compared with the fully fertilized plot (NPKSZnB).Tis similar or nonsignifcant output of sorghum biomass was the result of the nutrient nitrogen as it is responsible for vegetative growth and medium to high initial soil nutrients except nitrogen (Table 3) in the study site.However, the biomass yield decline was detected only from N omitted plots and unfertilized (control) plots.Te omission of nitrogen reduces biomass yield by 50.7% and 47.5% from boron omitted and fully fertilized (NPKSZnB) plots, respectively.However, compared to the control (unfertilized) plot, the application of NPSKZnB fertilizer boosted the sorghum biomass output by 50.5%.Tis outcome was consistent with the fndings of Robe and Ibsa [42], who showed the highest biomass yield (11,666 kg•ha −1 ) of sorghum was recorded after NPSZn application in the Sof district of Eastern Ethiopia.Similarly, Gebrekorkos, et al. [39] stated the most elevated sorghum biomass yield was obtained after the application of NPSZn in the irrigated agriculture of Raya valley, Northern Ethiopia.

Grain Yield.
Te results of the analysis of variance revealed that nutrient omission had a substantial impact on the grain production of sorghum.Reduced grain yield  Where AE N and AE P � nitrogen and phosphorus agronomic efciency respectively.
International Journal of Agronomy (2759 kg•ha −1 ) on control plots was noted, which was statically diferent from the N and P omitted plots (Table 5).
In addition to unfertilized plots, grain yields obtained from N omitted treatments were lower than any other fertilized treatments.Te Grain yield obtained from recommended NP treatment was at par with P, K, S, Zn, B, both Zn and B omitted plots, and NPSKZnB treated plots (Table 5).Te omission of N resulted in a 39.3% decrease in sorghum grain yield as compared to NPSKZnB treated plots.Te maximum decrease in crop growth and productivity owing to the omission of N emphasized the importance of N nutrient to sorghum, which is the most limiting nutrient for sorghum production over other nutrients [43].But, the omission of phosphorus, potassium, sulfur, zinc, boron, and both zinc and boron fertilizers did not show a clear and statistically signifcant impact on grain yield with site-specifc recommended rates of fertilizer.Te lowest yield in N omitted plots indicates that the application of nitrogen cannot be replaced by other nutrients in terms of sorghum yield.Tis could be associated with the efects of N in the synthesis of chlorophyll, photosynthesis, and assimilated production.In comparison with the other treatments, the higher yield loss was recorded in the unfertilized plots and omitted N plots.Tese results were expected since that they could be the result of poor nutrient supply in the soil, which did not satisfy the N demand of the sorghum crop.Te results of this research are associated with Haile-Selassie et al. [44], the nonsignifcant efect of phosphate fertilizer in felds having a higher inherent level of soil phosphorus.Tis might be the outcome of the excess application of phosphate fertilizer by farmers in the study area used to, which can lead to phosphorus build-up in the soil [45].
Tis outcome was consistent with Selassie's [46] fndings, which elucidated nitrogen as the supreme yield limiting nutrient for maize productivity on Alfsol of Northwestern Ethiopia.Te result also corroborated with Fageria [47], who explained nitrogen as one of the minerals that most severely restrict crop yields worldwide.Tis result is in line with other previous studies at Raya Kobo district (Getu et al. [34]).Tese fndings are also in accordance with Abera and Kassa [48].

Agronomic Efciency of Nitrogen (AEN).
Te mean agronomic efciency of N ranged between 11.8 and 19.7 kg grain kg −1 •N applied, depending on the quantity of fertilizer provided (Table 6).Te highest mean agronomic efciency (19.7 kg grain kg −1 •N) of N was attained from fully fertilized plots (NPKSZnB) with 34% increments over the lowest agronomic efciency of N (P omitted plot) (Table 6).Similarly, the agronomic efciency of N obtained from the recommended NP was higher than the agronomic efciency recorded by omitting P, K, S, Zn, B, and both Zn and B plots.Tis increment might be due to the lower rate of N in the recommended NP rate.Te result of this work also indicates that the agronomic efciency of nitrogen was reduced in the order of omission of P > S > both Zn and B > Zn > B > K by 34%, 28%, 21%, 18%, 8%, 6%, and 5%, respectively, as compared with the fully fertilized plots.As demonstrated in the current work, the omission of one of these nutrients which is P greatly decreases the agronomic efciency of nitrogen.Tus, the supply of P is essential to increase the AEN.
Te AEN recorded lies under an optimum range of agronomic efciency of cereal grain per unit of nitrogen which is 10-30 kg grain kg −1 nitrogen described by Dobermann [22].Tis author also stated that nitrogen use efciency decreases with increasing N rate.

Agronomic Efciency of phosphorus (AEP).
Te mean AEP ranged from −15.7-10.6 kg grain kg −1 P 2 O 5 (Table 6).Te maximum mean agronomic efciencies of Phosphorus were obtained from the application of macro and micro nutrients, with agronomic efciency increments over the N omitted plot by 97.6%.Similar fndings on the agronomic efciency of P for maize by Balemi et al. [49] confrmed the higher reduction of AEP in nitrogen omitted nitisols of Southwestern Ethiopia.

Nutrient Uptake
3.4.1.Nitrogen Uptake.Te present results indicated a substantial (P ≤ 0.01) diference in N uptake by nutrient omission (Table 7).Among the omitted nutrients, B omitted treatment had a higher total N uptake (174.8 kg•ha −1 ) without signifcantly diferent from the application of NPS, NPSKZnB, and NPZnB.Te lowest value of total N uptake was recorded with the control treatment (79.4 kg•ha −1 ).Tis work implies that the application of macronutrients in combination with micronutrients improves N uptake.Tis result inlines with Weldegebriel et al. [21] reported that total nutrient uptake had a signifcant response to the nutrient application and low nutrient uptake was obtained from control, P and N alone.Te same author stated that the application of NPKSZn fertilizer, considerably improved sorghum's ability to absorb nutrients.As a result, increasing nutrient uptake meant that there would be enough nutrients [50], who found that the application of micronutrients along with NPK fertilizers increases the concentration of nutrients in grain as well as stalk and so increases the total uptake of nutrients.

Phosphorus Uptake.
A wide variation in P uptake among treatments (P ≤ 0.01) was observed by the fertilizer treatments and control.Among the treatments, the highest overall P uptake (15.5 kg•ha −1 ) was recorded in a plot treated by NPSB (Zn omitted) and the lowest total P uptake (6.7 kg•ha −1 ) was recorded from unfertilized plots (Table 7).Tis study found that fertilization with N and P considerably boosted P absorption, indicating that these nutrients were more readily available or accessible in the soil [51].Tis indicates applied nitrogen may give an increased phosphorus uptake by plants.
Te present result conformed to that of Sharif et al. [52] in salt-afected soil.Sharif et al. [52] found that [52] plant P uptake by sorghum signifcantly increased over control.In addition, Haile Selassie et al. [44] confrmed N fertilizer gave considerably higher total P uptake.Fosu-Mensah and Mensah [51] also reported application of N and P considerably improved P grain absorption for maize due to their interaction with Haplic Lixisol.

Correlation of Yield and Yield Components of Sorghum.
According to an investigation of the association between yield components and grain yield, all of the yield components are signifcantly linked with grain yield (Table 8).Te present data showed that there was a very important (P ≤ 0.01) positive and linear correlation among yield and yield components of sorghum (Table 8).In view of that, grain yield was desirable and signifcantly positive correlated with biomass yield (r � 0.95 * * ), plant height (r � 0.89 * * ) and SPAD reading (r � 0.91 * * ) at P ≤ 0.01.A comparison of the correlation coefcient indicates that biomass gave a superior correlation coefcient (r � 0.95 * * ) to other yield components and plant height gave the lowest correlation coefcient (r � 0.85 * * ) than others.Te biomass yield of sorghum was substantially linked with plant height and SPAD reading at P ≤ 0.01.Te positive correlation of all possible pairs of characteristics indicated the prospect of a correlated response, such that the other positively correlated characteristic would increase with the improvement of one characteristic.Te outcomes of this investigation are consistent with Muhidin [53], who revealed that Grain yield showed highly [54] substantial and favorable connections with yield components mainly for leaf area index, plant height and biomass yield.

Conclusion and Recommendation
Considering the fndings of the current investigation, it is conceivable to conclude that nitrogen is the most yieldlimiting nutrient for sorghum production.Te nitrogen and phosphorous uptake of sorghum were considerably improved by the combined application of phosphorus and nitrogen at the study site.Te results showed that the mean agronomic efciency of nitrogen and phosphorus is reduced when N and P are omitted.
In addition, these fndings confrmed that omission of K, S, Zn, and B-containing fertilizer did not result in sorghum yield penalty, decreased agronomic N and P use efciency and nitrogen and phosphorus nutrient uptake from the recommended NP.Terefore, the fertility status of the soil must be monitored and those nutrients would be yieldlimiting in the future.Terefore, the target must be on only N containing fertilizers with phosphorus fertilizer (for soil fertility maintenance) to boost sorghum production and productivity.
Overall, the fndings showed that omitting of N results in a sizable yield penalty followed by omitting P and the application of nutrients using site specifc nutrient management technique should be used to increase sorghum production and proftability.As a result, to achieve the best sorghum yield for the study location, intensive research towards nitrogen fertilizer has to be done to determine the appropriate rates of nitrogen to meet the biological and economic optimum, while phosphorus could be used to keep fertility levels within a desirable range.International Journal of Agronomy 9

Figure 2 :
Figure 2: Mean monthly temperature and rainfall of Raya Kobo district in 2020 cropping season (source: Kobo meteorological station).

Table 1 :
Description of treatments and its purpose.

Table 2 :
Description of fertilizer rate applied in trial.

Table 3 :
Selected physicochemical property of the soil (before planting).

Table 4 :
Efect of nutrient omission on sorghum SPAD value and plant height.

Table 5 :
Efects of omission of nutrient on grain yield and above ground biomass yield of sorghum..B: means in the columns that are denoted by the same letter do not difer substantially at P ≤ 0.05.Where * * � signifcant at P ≤ 0.01, N* � signifcant at P ≤ 0.05.

Table 6 :
Agronomic nitrogen and phosphorus efciency of sorghum as infuenced by omission of nutrients.

Table 7 :
Nutrient uptake of sorghum as infuenced by nutrient omission.