BY B. O. UKEM DEPT. OF SOIL SCIENCE, FACULTY OF AGRICULTURE/INSTITUTE FOR AGRICULTURAL RESEARCH, AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA Responses of Sorghum to Combined Application of A Nutrient Solution and Solid NPK Fertilizers in a Tropical Environment

Introduction  In the savanna soil of Nigeria, micronutrient deficiency was not noticed in the past but with the intensification of agriculture over the years, crop exploitation of soil available nutrients, crop removal and adverse cultural practices of farmers have led to the incidence of micronutrient deficiency with negative effect on growth, yield and quality of crops.  Sorghum (Sorghum bicolor) cultivation in Nigeria has continued to rise over the years particularly in the last decade with an estimated land area of about 6 – 6.5 million hectares cropped to sorghum annually and farmers yields have risen tremendously from about 3.8 – 6.8 million metric tons of dry grains from the land area under cultivation (NBS, 2010).  With limited land resources, the impact of continuous cultivation has contributed adversely to the rapid depletion and imbalances of soil plant nutrients which consequently poses a serious threat to the soil fertility status and thereby limiting sustainable crop production practices.  The micronutrients present in the NPK fertilizers are mainly as incidental elements. Also, their fixation with phosphate anions in the soil often renders them unavailable to plants which therefore necessitates foliar application of a nutrient solution to enhance micronutrients availability for crop use.

The objectives of the study are: 1. To test the effectiveness of Algifol nutrient solution as a single fertilizer and in combinations with solid NPK on growth and yield of sorghum under tropical conditions. 2. To test the effect of single and combined application rates of Algifol nutrient solution and NPK on growth and yield of sorghum. 3. To determine the optimum application rate of Algifol nutrient solution in the northern guinea savanna of Nigeria.

Materials and Method Study Area:  The experiment was conducted at the Institute for Experimental Res. Samaru Located in the Northern Guinea Sav. agro-ecological zone of Nigeria. Soil Characteristics:  Soil of the zone is classified as Alfisol Ojanuga (1979). The soil is low in organic matter content, total N and available P but moderate in exchangeable bases. Clay mineralogy is of low activity.  Soil is therefore low in fertility.  Soil data is in Table 1. nutrient composition of Algifol is in Table 2 Fertilizer Rates, Treatments and Design:  Algifol nutrient solution rates were 5, 10, 15 and 20ml/100ml of water( 1 / 2, 1, 1 1 / 2 and 2Alg) or 0.5, 1.0, 1.5 and 2.0 litres/ha Algifol and ¼, ½, ¾ and 1 or Full NPK at the rate of 150, 60, 60kg/ha N, P 2 O 5 and K 2 O respectively.  solid fertilizer levels were ¼NPK, ½NPK, ¾NPK and Full NPK at the rate 64:32:30kg ha -1 N, P 2 O 5 and K 2 O representing (16, 8, 7.5, kg ha -1 N, P 2 O 5 and K 2 O); (32, 16, 15 kg ha -1 N, P 2 O 5 and K 2 O); (48, 24, 22.5, kg ha -1 N, P 2 O 5 and K 2 O) and (64, 32, 30 kg ha -1 N, P 2 O 5 and K 2 O). Urea, Single Superphosphate (SSP) and Muriate of Potash (MOP) were the fertilizer materials used. Nitrogen was split applied in bands at 2WAP and 8WAP. SSP and MOP were band applied at planting.  The treatments were laid in a Randomized Completely Blocked Design (RCBD) with three replications.

 Table 2 Chemical composition of Algifol nutrient solution Chemical ComponentsValues Phosphorus (mg kg -1 )9.88 Potassium (cmol kg -1 )3,268 Calcium (cmol kg -1 )647 Sodium (cmol kg -1 )600 Zinc (mg kg -1 )3.75 Iron (mg kg -1 )20.00 Manganese (mg kg -1 )6.25 Copper (mg kg -1 )2.50

 Table 3 Physico-chemical characteristics of soil from the experimental site (20cm soil depth) Soil PropertyValues Sand (g kg -1 )371 Silt (g kg -1 )400 Clay (g kg -1 )229 Textural ClassLoam pH (1:2.5 w/v H 2 O)5.0 PH (1:2.5 w/v, 0.01M CaCl 2 )4.7 Organic Carbon (g kg -1 )5.4 Total N (g kg -1 )1.27 Bray - 1 Available P (mg kg -1 )2.69 Exchangeable Ca (cmol kg -1 )3.60 Exchangeable Mg (cmol kg -1 )0.39 Exchangeable K (cmol kg -1 )0.47 Exchangeable Na (cmol kg -1 )0.21 CEC (cmol kg -1 )4.67 Extractable Zn (mg kg -1 )6.8 Extractable Fe (mg kg -1 )18.0 Extractable Cu (mg kg -1 )2.0 Extractable Mn (mg kg -1 )18.0

Results and Discussion Plant Height  The response of plant height to treatments is presented in Table 4. The results show that the treatments had a significant effect(P=0.05) at 7WAP, but at 9WAP, the effect was highly significant (P=0.01). It is obvious from the result that the fertilizer treatments had a positive impact on the vegetative growth of the plant.  There was a positive response from the soil applied solid NPK doses at 9WAP though the trend of increase in height was not consistent with treatments. The complementary application of nutrient solution and NPK seemed to be nutritionally more effective as best result was recorded from 1Alg + ¾NPK at 9WAP (Table 4). This may be related to the rather low fertility conditions of the soil (Tarfa et al., 2001).  From the results, control consistently recorded the shortest height in relation to other treatments because of the low initial fertility level of the soil (Table 3). It is therefore expedient to apply inorganic fertilizers in suitable combinations to boost adequate vegetative growth.

 Table 4 Effect of the nutrient solution and NPK on plant height and girth Plant heightPlant girth cm WAP Trt rate7979 Control bc ef 6.43 c 7.61 f ½ Alg a b 6.66 bc 8.39 bcde 1 Alg abc g 7.05 ab 8.90 ab 1½ Alg ab f 6.47 c 7.90 def 2 Alg bc ef 6.99 abc 8.77 ab ¼ NPK bc de 6.88 abc 7.89 def ½ NPK bc b 7.16 ab 8.02 cdef ¾ NPK bc ef 7.05 abc 7.85 ef Full NPK bc bc 6.97 abc 9.02 a ½ Alg + Full NPK bc cd 6.92 abc 8.46 bc 1 Alg + ¾ NPK abc a 6.98 abc 7.94 cdef 1½ Alg + ½ NPK c h 7.29 a 9.24 a 2 Alg + ¼ NPK ab f 6.97 abc 8.42 bcd F ratio**** SE 

Stem Girth  Effect of the fertilizer treatments on stem girth was significant (P=0.05) at 7WAP and at 9WAP, the effect was highly significant (P=0.01) (Table 4). In both periods, the control had the lowest girth compared to the positive responses from the fertilizer treatments. The low response recorded from control is attributed to the low fertility conditions of the soil. And as such, amendments of the soil with either organic or inorganic sources of nutrients should improve its nutrient holding status for efficient crop performance.  Complementary application of both nutrient solution and NPK made a significant impact on the growth of sorghum in a tropical savanna soil having been able to furnish the desired plant nutrients and in their suitable ratios to meet crop requirements.

Grain Yield  Grain yield responded positively and significantly (P=0.05) to the treatments (Table 5). Response to nutrient solution levels alone showed a significant increase from ½ rate Alg up to 1½ rate Alg with yield increases ranging from 1162, 1308 to 1675kg ha -1 grains (37%, 39% to 45%) yield respectively over the control (Table 5). The decrease in grain yield recorded from 2 rate Alg may be due to leaf burning effect initiated by the higher level of the nutrient solution and thereby leading to the destruction of photosynthetic sites of the plant with a consequent yield reduction. A similar effect had already been reported (Effiong et al., 2006; Brady and Weil, 2005).  The response from the treatment combinations showed that low levels of nutrient solution in combination with higher levels of NPK were superior to higher levels of nutrient solution combining with reduced levels of NPK. It is therefore obvious that minimal levels of foliar solutions are more efficient than the higher doses in plant nutrition especially in combination with NPK doses.

Table 5 Effect of the nutrient solution and NPK on head, grain and stover yields HeadGrainStover Trt rateYield (kgha -1 ) Control2,480 c 2,016 c 10,000 c ½ Alg4,196 abc 3,178 abc 12,333 bc 1 Alg4,052 abc 3,324 abc 11,000 bc 1½ Alg4,535 ab 3,691 ab 9,667 c 2 Alg3,167 bc 2,507 bc 11,833 bc ¼ NPK3,496 abc 3,034 abc 12,667 bc ½ NPK2,994 c 2,410 bc 14,667 bc ¾ NPK4,504 ab 3,379 abc 13,333 bc Full NPK5,023 a 4,062 a 15,667 b ½ Alg + Full NPK4,140 abc 3,634 ab 15,500 b 1 Alg + ¾ NPK4,083 abc 3,155 abc 20,333 a 1½ Alg + ½ NPK3,113 bc 2,541 bc 9,833 c 2 Alg + ¼ NPK3,283 bc 2,694 abc 12,667 bc F ratio**** SE

Stover Yield  The effect of the fertilizer treatments on plant dry matter was highly significant (P=0.01). Highest yield was obtained from the combined application of 1Alg + ¾NPK while the least performance was obtained from 1½Alg dose though its treatment mean was not significantly different from the control (Table 5).  The result further shows that nutrient solution or NPK alone could not achieve the expected DMY that was achievable with NPK + nutrient solution, thus suggesting the need for an integrated system of crop production that combines foliarly applied nutrient solutions and soil applied NPK for the savanna soils.

Conclusion  The trial has revealed that in many parameters measured, control recorded the lowest performance relative to actual fertilizer treatments. It is evident from the results that fertilizer application improved the growth and yield of sorghum in the northern guinea savanna soil.  Even though full rate NPK recorded the highest grain yield, the complementary application of nutrient solution and NPK was more effective in achieving adequate plant height, girth and stover.  Such treatment combinations are optimum especially under tropical conditions in ensuring a healthy crop growth and sustainable yields.  In view of the effective performance of the complementary application of nutrient solution and NPK, there is therefore the need to explore such combinations for a wider use in tropical soils.

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