The experiments were conducted over three growing seasons (2016-2018) at two locations within the Sudan savanna agroecological zone of Nigeria. The first location was the ICRISAT research field situated within the Institute for Agricultural Research (IAR) Station, Wasai, Minjibir (Latitude 12.17° N and Longitude 8.65° E). The second location was the ICRISAT research field situated within Bayero University Kano (BUK) (Latitude 12.98° N and Longitude 9.75° E). Weather data was collected from Campbell Scientific Automated Weather Stations installed within a 2 km radius of the experiment sites.

The experimental design was a split-split plot with four replications. The year of the experiment was taken as the main plot, fertilizer application strategy as the sub-plot and the sorghum varieties tested the sub-sub-plot. The years of the experiment considered as the main plot were Year 1 (2016), Year 2 (2017), and Year 3 (2018), respectively. The fertilizer sources (organic and inorganic), application strategies (sole and combination), and varying quantities considered as sub-plots are nine fertilizer application strategies and a control (no fertilizer) applied using micro-dossing techniques. The fertilization treatments (Table 1a) include F1 (Control); F2 (Cattle manure 50 g/hill + Poultry manure 50 g/hill); F3 (Cattle manure 100 g/hill); F4 (NPK 80:60:60); F5 (NPK 3 g/hill); F6 (NPK 3 g/hill + Cattle manure 100 g/hill); F7 (Poultry 100 g/hill); F8 (Poultry manure 100 g/hill + NPK 3 g/hill); F9 (Poultry manure 150 g/hill) and F10 (Poultry manure 50 g/hill).The three sorghum varieties tested as sub-sub-plot included: CSR 01, Improved Deko, and Local Kaura. The gross size of each sub-sub plot was 15 m², (4 rows of 5 m long and rows spaced at 75 cm apart). Sowing was done at 30 cm between hills, having a total plant population of 44,444 hills ha^-1.

Soil samples were taken annually at random before the establishment of the experiment at three different depths of 0-20 cm, 20-40 cm, and 40-60 cm, respectively, and analyzed for soil Physico-chemical properties. Organic manure (cattle and poultry) used in the experiment was also analyzed annually for their chemical properties such as total N, available P, exchangeable cations, percentage of organic carbon, and pH before being used for the experiment. The fields were ploughed, disc-harrowed, and ridged at 75 cm inter-row spacing. Sowing was done during the first cropping season on the 18^th and 21^st of June 2016 at BUK and Minjibir, respectively. In the second cropping season, it was done on the 28^th of June at BUK and the 20^th of June at Minjibir in 2017. The third cropping season was sown on the 27^th of June at BUK and the 20^th of June at Minjibir in 2018. Seeds were sown at 5-7 seeds per hole at a depth of 3 cm to 5 cm and thinned to 2 plants per hill at 2-3 weeks after sowing (WAS). To maintain optimum plant population, where necessary, gap filling was done 3 to 4 days after sowing. For the plots with organic fertilizers, all the fertilizers were applied in full at 5 cm from the seed at sowing. For those plots with inorganic fertilizer, micro-doses were applied 5 cm away from the seed at sowing, except for the plots with NPK at the rate of 80:60:60 on which the full doses of P and K together with 60 kg N ha^-1 were applied through drilling at sowing, while the balance of 20 kg N ha^-1 was applied as Urea at 5 WAS. Weeding was done manually to keep the field weed-free. At both experimental locations, grain and stalk yields were measured from two harvested rows (net plot) at the center of each plot [7.5 m² area (5 m × 1.5 m)]. Panicles, grain, and stalk were sun-dried for two weeks before threshing. Grain yield (kg ha⁻¹) and 1000 seed weight (g) were determined. All the data were subjected to analysis of variance (ANOVA) using the GENSTAT analytical tool (19^th edition). Year; fertilizer type, combination, quantities; and variety were taken as factors to determine the level of significance at 5% probability. Fisher s least-significant difference (LSD) was computed where the p values were significant at the p = 0.05 level of probability 22.

Water use efficiencies of grain for the years of experiment, fertilizer micro-dose application strategies, and the tested varieties between sowing and physiological maturity were calculated. Firstly, we compute daily reference crop evapotranspiration (ET_o) using the daily records of minimum temperature. The recommended crop coefficient (K_c) for sorghum was calculated using the methods described by 14 and was multiplied by the computed daily reference evapotranspiration (ET_o) using the methods described by 5 to compute crop evapotranspiration (ET_c) using equation (1). Therefore, ET_c was calculated using the equation below:

ET_c = K_c ET_o (1)

where,

ET_c crop evapotranspiration (mm),

K_c crop coefficient (dimensionless),

ET_o reference crop evapotranspiration (mm d^-1).

WUE was calculated using the following equations by 28 and was reported as kg grain mm^-1 of rain received.

WUE = (2)

where,

GY is grain yield (kg ha⁻¹),

ET_c is crop evapotranspiration (mm).

The nitrogen use efficiency (NUE) was calculated as per the following formula described by 35 and reported as kg grain kg^-1 of N applied.

NUE= (3)

where,

Y_f is grain yield (kg ha⁻¹) in the fertilized plot,

Y_c is grain yield (kg ha⁻¹) in the control plot,

N_a is nitrogen applied (kg ha^-1).

For the benefit-cost ratio, the methods described by 16 were adopted, in which the financial concepts are defined by equations (4) and (5), given that total revenue refers to the sum of unit price multiplied by the quantity of grain and stalk yields produced.

Total Revenue (TR) = (4)

where

Rg is the revenue generated from grain,

Rs is the revenue generated from the stalk.

Total Cost of Production (CP) is the sum of the costs incurred during the production of the sorghum, such as tillage, planting, crop treatments, herbicides, seeds, and labor, among others.

Net economic returns (NERs) are the difference between TR and TCP.

The benefit-cost ratio was therefore calculated using the below formula:

B:C = (5)where,

TR is the total revenue generated from grain and stalk (Naira ha^-1),

TCP is the total cost of production of the sorghum (Naira ha^-1).

The soil types in the experimental sites (Table 1b and Table 1c) were classified as sandy loam in texture for the depths of 0-20 cm and 20-40 cm in both locations. The texture was documented as being loamy sand to loamy clay sand for a depth of 40-60 cm in both locations. This soil textural class falls within the recommended textural classes suitable for producing sorghum. The soil's pH of the locations was between 5.78 and 7.07, with a depth of 40-60 cm in 2016 and 2018 in the same BUK. These pH values are slightly basic to slightly alkaline, which is appropriate to produce sorghum as documented by 27. The experimental areas had low to medium concentrations of soil organic carbon, low concentrations of total nitrogen, and available phosphorus was varied.

The cattle manure employed (Table 1d) had a pH that was between 6.2 and 8.4, which is indicative of acidic to basic conditions, while the poultry manure had a pH that was between 8.2 and 9.8, which is indicative of basic to acidic conditions. The pH of the manure was primarily affected by the degree of fermentation or digestion. The higher pH of the poultry manure is also beneficial to soil health in acidic soil, this is of great importance in the maintenance of soil fertility. Also, higher percentages of N were observed in poultry manure, which was between 1.2% and 1.6%, the highest percentage of N was observed in 2018 in cattle manure. The percentage of N in poultry manure was over twice the amount in cattle manure. The poultry's excretion contains both pee and urine, this makes it different than the cattle's manure regarding the N composition. However, the concentration of cattle manure was higher in P and K than that of poultry manure. The chemical composition of the analysis demonstrated the value of poultry manure as a soil enhancer of fertility and would be of great importance in organic farming and the recycling of nutrients. The amount of N per season was determined by analyzing the cattle and poultry manure as well as the inorganic fertilizer (Table 2). The high concentration of poultry manure (150 g per hill) was comparable to about 6 t ha^-1, this produced the highest application rate of 95 kgNha^-1, which was higher than the recommended rate of 80 kgNha^-1. This was followed by hybridization of medium application rates of poultry manure F8 (average of 83 kgNha^-1), followed by F10 (average of 32 kg ha^-1), F3 (average of 31 kg ha^-1), and F5 (average of 20 kg ha^-1) had the lowest N application of any fertilizer application.

The rainfall was highly variable and followed a single-modal pattern, but a slight drop was observed in July due to a long dry spell in 2016 and 2018 at BUK in 2018 and an early pick of rainfall observed in 2016 and 2017 in Minjibir. More precipitation was received in 2016 and 2017 at Minjibir than it was in BUK, except for 2018 when the precipitation recorded at BUK was higher than at Minjibir. Despite the volume of precipitation received in both experimental sites, most of the precipitation was of short duration and high intensity between June and August, with over 70% of the total precipitation in BUK and 77%-82% of the total precipitation in Minjibir. The total annual rainfall volume received during the experimental periods at the BUK and Minjibir sites was between 439 mm and 573 mm, which is greater than the water requirement for optimal yield of sorghum in the semi-arid region 26. The total volume of rainfall was split between 36 and 53 days. Temperature is another significant weather component that affects crop growth, development, and productivity because of its role in the physical and chemical processes within the plants. These processes, in turn, affect the chemical reactions in the plants. Every plant species has a specific maximum, optimal, and minimum temperature range for its typical growth and development at a particular stage of its life cycle. During the 3-year growing season, the average monthly minimum temperatures ranged from 15.1 to 23.7 °C in the BUK site and 14.5 to 24.4 °C in the Minjibir site (Table 3a and Table 3b). The maximum temperature was between 30.4 and 36.4 °C in BUK, and between 30.4 and 37 °C in Minjibir. The temperature was situated within the reported range of sorghum by 4. This implies that the current study concurred with both higher and lower temperatures and base thresholds for sorghum in both experimental areas.

Table 4 presents the effect of year, fertilizer treatment, and variety on the 1000 seed weight, grain, and stalk yields of sorghum. Significant differences (p = 0.002) were observed between the years of the experiment regarding the weight of 1000 seeds and the yield of grain (p = 0.001) in BUK. However, the years had no significant effect on the stalk yield in BUK or the weight of 1000 seeds, nor the yield of grain or stalk in Minjibir. Local variety had a higher average weight of seeds than improved varieties (30.4 g and 31.5 g at BUK and Minjibir, respectively). The lowest 1000-seed weight (28.6 g and 26.9 g at BUK and Minjibir, respectively) was achieved by improved Deko. The application of fertilizer had no significant impact on the weight of the seed. These outcomes agreed with the findings of 3 reported no significant differences in the 1000-seed weight of sorghums due to the utilization of fertilizer in BUK and Minjibir, Local Kaura sorghum had a higher 1000-seed weight than other varieties from experimental locations. Years, strategies for fertilization, and varieties of sorghum have a significant impact on yields of grain (Table 4). In BUK. In Minjibir, the years had no significant impact on the mean yield of grain crops, but there were significant differences (p < 0.001) between the treatments of fertilizer as well as between the varieties of sorghum. The interaction between the year and the application strategy for fertilizers, as well as the sorghum varieties, was not significant in BUK but was significant in Minjibir. The highest average yield of grain in 2017 was 2.05 million kg ha^-1, which increased by 32 percent compared to 2018 and increased by 40 percent compared to 2016, respectively. These findings could be attributed to environmental effects like the soil and weather patterns, particularly the distribution of rainfall that was more beneficial in 2017 than in 2016 and 2018. For example, in the 2017 experimental year, the soil's pH ranges were 6.1- 6.3 (Table 2) across the sampling depths, which are in the appropriate range of soil pH for releasing nutrients that are fast in the soil system 20. Additionally, 70% of the precipitation total was received in 53 days of rain during the experimental period, which was lower in 2016 and 2018, respectively. The volume of rainfall received during the experimental years was found adequate to produce high grain yields, previous findings by 3 reported that the distribution of the rainfall supersedes its total seasonal volume in ensuring higher grain yield is produced.

Highly significant differences (p < 0.001) in the grain yield were observed between applications of fertilizer in both locations. The application of 100 g of poultry manure plus 3 g of NPK per hill (F8) resulted in the highest average yield of 2243 kg ha^-1 and 2250 kg ha^-1 in BUK and Minjibir, respectively. 31 showed that the micro-dosing of P fertilizers on pearl millet in soil with an acidic composition, in a sandy area, at a rate of 3-5 kg ha^-1 produced almost the same yield as the broadcasting of P fertilizer at a rate of 15-20 kg ha^-1, which is the typical rate in the Sahel 8. Greater success was observed in the present study's microdosing of NPK 3 g per hill, this produced a higher yield of grain in both locations than the recommended amount of fertilizer applied. The treatment F8 increased the mean yield of grain by 12%-86% in BUK and 29%-132 in Minjibir. The application of 100 g of poultry manure plus 3 g of NPK per hill was equivalent to the utilization of 80 kg N ha^-1. This concords with the findings of 3, in a similar environment, who documented that sorghum had the greatest yield at the application of 80 kg N ha^-1. The application of 100 g of poultry manure per hill produced significantly greater yields than the utilization of 100 g of cattle manure per hill, with 20 and 30 percent higher yields in BUK and Minjibir, respectively. This demonstrates the superiority of poultry manure over cattle manure as a form of organic fertilizer. Conversely, the combination of 100 g poultry manure with 3 g NPK per hill increased the yield significantly (13 and 55 percent for BUK and Minjibir, respectively) compared to sole poultry manure. This is of special significance to farmers who may not have the capacity to apply 150 g of poultry manure per hill (about 6000 kg ha^-1). A mixture of poultry manure and inorganic fertilizer should be considered for the high productivity of sorghum. Among the varieties of sorghum, the Improved Deko had the highest average yield of 2548 kg ha^-1 and 2096 kg ha^-1 at BUK and Minjibir, respectively. The capacity of Improved Deko to produce higher than CSR 01 and local Kaura in both locations can be attributed to its earlier flowering behaviour, this behaviour occurred while the rain was stopped. However, the local Kaura's used in the experiment had been observed to adapt to the area and had a high degree of drought tolerance, this helped it to complete its growth cycle despite the lack of rainfall.

Additionally, the effect of the year was not significant in BUK, but Minjibir had a significant interaction with the year (Table 5). The highest average grain yield on all varieties was achieved in F8 (100 g of poultry manure plus 3 g of NPK per hill). The highest average grain yield for CSR 01 was documented as 1952 kg ha^-1, which was obtained in 2017; 2950 kg ha^-1 was the highest yield for Improved Deko in the same year, and 3238 kg ha^-1 was the highest yield for local Kaura in 2018. Table 5 demonstrated that the fertilizers affected the stalk yield, the strategy of applying fertilizers increased the stalk yield compared to the zero-fertilizer strategy in both locations. The highest average yield of stalks was achieved with the application of 100 g of poultry manure plus 3 g of NPK per hill, this produced 11,688 kg ha^-1 and 10,239 kg ha^-1, which were 39% and 48 % greater than the control that produced the least value in both locations. Among the varieties of sorghum, CSR 01 had the highest yield of stalks with a mean value of 9970 kg ha^-1, while the lowest value was observed to be 8219 kg ha^-1 and was derived from Improved Deko at BUK, while in Minjibir, Improved Deko produced the highest yield of stalks with a mean value of 11,965 kg ha^-1, and the lowest value was 7857 kg ha^-1 from local Kaura.

Table 6 depicts the contrast analysis that compares the mean grain yields of selected block fertilizer strategies. The application of sole poultry manure increased the average yield of grain by over 100%, from 1593 kg ha^-1 to 2428 kg ha^-1. Similarly, significant differences between sole poultry manure (1911 kg ha-1) and the combination of poultry manure 100 g plus 3 g NPK per hill (2302 kg ha^-1) were observed, which indicated a 17% increase in yield for a 3 g NPK per hill applied to sole poultry. In both locations, significant differences were observed between the means of sole poultry manure applications and controls (no fertilizer). In BUK, significant differences were observed between the application of sole poultry manure (average of 1911 kg ha^-1) and zero fertilizer (1208 kg ha^-1) which indicated a 37% increase in yield.

Table 8 revealed significant differences among the fertilizer application strategies, and sorghum varieties forTotal Cost of Production (TCP), Total Revenue Generated (TR), Net Profit (NP), and Benefit: Cost Ratio (B: C), in both locations. The application of NPK at 3 g per hill (F5) produced the highest mean net profit (N246,888 and N276,522) and benefit-cost (3.21 and 3.58) ratio while the poultry manure (F9) estimated the least net profit (N 104,779 and N 114,786) and benefit-cost (1.4 and 1.5) ratio, both at BUK and Minjibir, respectively. The results further revealed that the application of poultry manure (100 g per hill) plus 3 g per hill of NPK (F8) had the highest mean total revenue (TR) generated while the lowest TR was obtained from control (zero fertilizer treatment). It was observed that F8 (poultry manure (100 g per hill) plus 3 g per hill of NPK) produced the highest mean grain and stalk yields and estimated the highest mean TR in both experimental sites but did not proportionate to higher NP and B: C ratio. These results were attributed to the high cost of production, precisely the high cost of fertilizers and poultry manure in the area, and agreed with the findings by 25 who also reported less profit gained on sorghum when produced at a higher cost.

Among the varieties, Improved Deko had the highest mean net profit and benefit-cost ratio while CSR 01 had the lowest. In BUK, Improved Deko had a mean NP of N241,578 and B: C of 2.6 while CSR 01 had a mean NP of N154,818, and B: C of 2.0. Similarly, at Minjibir, Improved Deko had a mean NP of N280,287 and B: C of 3.0 while the lowest mean values were produced by CSR 01 with an NP of N114,920, and B: C of 2.1. This suggests a higher return on investment by cultivating Improved Deko than other varieties (CSR 01 and local Kaura). This was attributed to the high mean grain yield produced by Improved Deko. This agrees with the findings of 19 who reported higher benefit-cost ratios on sorghum varieties with high grain yields.