BY

B. O. UKEMDEPT. 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 MethodStudy 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, 11/2 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, P2O5 and K2O respectively.

solid fertilizer levels were ¼NPK, ½NPK, ¾NPK and Full NPK at the rate 64:32:30kg ha-1 N, P2O5 and K2O representing (16, 8, 7.5, kg ha-1 N, P2 O5 and K2O); (32, 16, 15 kg ha-1 N, P2 O5 and K2O); (48, 24, 22.5, kg ha-1 N, P2 O5 and K2O) and (64, 32, 30 kg ha-1 N, P2 O5 and K2O). 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 Components Values

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 Property Values

Sand (g kg-1) 371

Silt (g kg-1) 400

Clay (g kg-1) 229

Textural Class Loam

pH (1:2.5 w/v H2O) 5.0

PH (1:2.5 w/v, 0.01M CaCl2) 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 DiscussionPlant 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 height Plant girth

cm

WAP

Trt rate 7 9 7 9

Control 218.06bc 335.05ef 6.43c 7.61f

½ Alg 338.09a 374.57b 6.66bc 8.39bcde

1 Alg 237.78abc 307.06g 7.05ab 8.90ab

1½ Alg 270.69ab 326.02f 6.47c 7.90def

2 Alg 222.93bc 333.09ef 6.99abc 8.77ab

¼ NPK 207.04bc 345.82de 6.88abc 7.89def

½ NPK 195.14bc 373.97b 7.16ab 8.02cdef

¾ NPK 220.35bc 329.05ef 7.05abc 7.85ef

Full NPK 196.28bc 362.78bc 6.97abc 9.02a

½ Alg + Full NPK 210.59bc 351.95cd 6.92abc 8.46bc

1 Alg + ¾ NPK 241.24abc 408.51a 6.98abc 7.94cdef

1½ Alg + ½ NPK 153.17c 283.82h 7.29a 9.24a

2 Alg + ¼ NPK 268.58ab 328.60f 6.97abc 8.42bcd

F ratio * ** * **

SE 33.78 5.33 0.17 0.17

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

Head Grain Stover

Trt rate Yield (kgha-1)

Control 2,480c 2,016c 10,000c

½ Alg 4,196abc 3,178abc 12,333bc

1 Alg 4,052abc 3,324abc 11,000bc

1½ Alg 4,535ab 3,691ab 9,667c

2 Alg 3,167bc 2,507bc 11,833bc

¼ NPK 3,496abc 3,034abc 12,667bc

½ NPK 2,994c 2,410bc 14,667bc

¾ NPK 4,504ab 3,379abc 13,333bc

Full NPK 5,023a 4,062a 15,667b

½ Alg + Full NPK 4,140abc 3,634ab 15,500b

1 Alg + ¾ NPK 4,083abc 3,155abc 20,333a

1½ Alg + ½ NPK 3,113bc 2,541bc 9,833c

2 Alg + ¼ NPK 3,283bc 2,694abc 12,667bc

F ratio * * **

SE + 514 418 1.53

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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