INTRODUCTION:

Many consumers consider organically produced fruits and vegetables to be healthier and safer than conventionally grown fruits. Because of this, consumers are willing to pay more for organically grown crop (Whole food market, 2000). What is perhaps most surprising is just what a healthy food watermelon actually is. Sweet, juicy watermelon is actually packed with some of the most important antioxidants in nature. Watermelon is an excellent source of vitamin C and a very good source of vitamin A, notably due to its high concentration of beta-carotene. Pink watermelon is also a source of potent carotenoid antioxidant and lycopene. These powerful antioxidants move through the body and neutralize free radicals. Free radicals are substances in the body that can cause a great deal of damage. They are able to oxidize cholesterol, making it stick to the walls of blood-vessel, where it can lead to heart attacks or strokes. They can add to the severity of asthma attacks by causing the airways to clamp down and close. They can increase the inflammation that occurs in osteoarthritis and rheumatoid arthritis and cause most of the joint damage that occurs in these conditions and they can damage cells lining the colon, turning them into cancer cells. Fortunately, vitamin C and beta-carotene are very good at getting rid of these harmful molecules and can prevent the damage they would otherwise cause. (http://en.academic.ru ).Watermelon is currently grown in all continents throughout the warm regions of the world (http://www.nda.agric.za) Watermelon made its first appearance in an English dictionary in 1615(Sabo et al, 2012).

A one-cup serving (only 45 calories by the way), contains the following:

· Vitamin A – 17% of the recommended daily requirement.

· Vitamin B1 (thiamine) – 3% of the recommended daily requirement.

· Vitamin B6 – 3% of the recommended daily requirement.

· Vitamin C – 20% of the recommended daily requirement.

· Potassium – 5% of the recommended daily requirement.

· Magnesium – 4% of the recommended daily requirement.

It also contains a substantial amount of lycopene, a very powerful antioxidant that play a role in prevention of both heart disease and some types of cancer. The levels of lycopene found in a pink and red watermelon are actually even higher than, those found in tomatoes! www.watermelon.org. Watermelon is recommended in weight loss diets because of its 93% water content, fiber, low calories and carbohydrates. Watermelons contain Vitamins: pro-vitamin A and C. Minerals: potassium, magnesium, calcium, phosphorus, iron and sodium. Others: folic acid, beta-carotenes, lycopene (antioxidant), ascorbic acid, riboflavin, thiamine and niamine. Watermelon has beneficial properties for bone, tissue and nervous system grown in children, liquid retention problems (diuretic), Intestinal transit and constipation problems (strong laxative properties). Blood pressure, Kidney stones, Prostatitis and Cystitis, Kidney deficiency. Bladder cancer, Expels uric acid, Nervous system, Anti-carcinogenic, Detoxing and purifying. Preventing cardiovascular and degenerative problems and strengthening the immune system. (Grupo roseger 2014)

However, advocation for an integral use of inorganic fertilizer and organic manure for supply of adequate quantities of plant nutrient is required to sustain maximum crop productivity and profitability while minimizing environmental impact from nutrient use (Taylor et al., 2006). Watermelon is one of the commercial crops used for many purposes and by many people but the production is restricted to some areas in Nigeria due to climatic condition and geographical location of the area, which favor their production. Most savannah soils are poorer in terms of fertility (Abdel et al., 2005). Ideas of the optimum fertility level needed for vegetative production can be gain from the quantities of nutrient removed by the crop. The removal may vary according to the soil nutrient content and their availability as affected by soil moisture and temperature (Donard and Escor, 1988; Ifitihar, et al., 2004). Watermelon responds positively to the fertilizer application, the dose defend on the soil type, climate and system of planting. In general, high Nitrogen under high temperature condition promote maleness in flowering and lower the number of females or perfect flowers, resulting in low fruit set (Chadha et al., 2006). A significant increase in vine length, number of leaves, leaf area and number of branches was recorded with increase in fertilizer application (Lawal, 2000). Similarly, a remarkable increase in vine length with increase in Nitrogen application was reported (Abdel et al., 2005). Manure from livestock is commonly use as a fertilizer in arable field as a source of nutrients. Cowdung has traditionally been an important source of nitrogen (N) and other nutrients. Where possible, joint applications of manure and inorganic fertilizers to make Nitrogen available in the soil for uptake by crop plants is important. Continuous cultivation of land has resulted in accelerated soil nutrients depletions, decline in soil organic matter content, destruction of physical structure and reduction in crop productivity. Manure from cattle was traditionally used as fertilizer to ameliorate many of problems of soil fertility either alone or in combination with inorganic inputs. Manure and urine of herbivores mammals, often featured as a key ecosystem component linking the livestock and arable components Ewulo (2005). Soil in northern guinea and sub-saharan savannah of Nigeria are poor in native nutrient and low amount of organic matter content (Dauda et at., 2009). Apart from the above mentioned shortcoming in production, areas that favor the production in both climatic and geographical are also facing problems of fertilization. Because of this, production of watermelon is not optimal in areas of production in Nigeria. To produce an optimum yield of watermelon there is need to use both organic and inorganic fertilizer. Since farmyard manure or organic manure (cowdung) and NPK fertilizer has been known to enhance productivity of crops. To note that extensive use of inorganic fertilizer has a depressing effect on yield. This causes reduction in number of fruits, delays and reduces fruits setting, which subsequently delay ripening, and leads to heavy vegetative growth. Moreover, the growth and yield of watermelon should not be overlooking, from this direction. The main aim of the experiment was to determine the effect of Different Levels of cowdung and NPK fertilizer on the growth and yield of watermelon.

MATERIALS AND METHODS:

The field experiment was conducted at Deda,Yamaltu-Deba local government, Gombe State, during the rainy season of 2012. Gombe state is located at approximately latitude 10° - 18 N and longitudes 11⁰3 East at the altitude of 830 M above the Sea level in the Northern Guinea Savannah ecological Zone of Nigeria. The treatments comprised of four levels of compound fertilizer (NPK 20:10:10) at 0, 100, 150 and 200 kg/ha, four levels of organic fertilizer (cow dung) at 2.5, 5, 7.5 and 10 tons/ha with three combinations of cowdung and NPK at 1.25 t + 50 kg, 2.5 t + 75 kg and 3.75 t + 100 kg/ha, factorially combined into a total of eleven (11) treatments combination and laid out in a randomized complete block design (R C B D) with three replications. The variety used was sugar baby early mature within 70-75 days. The different levels of cowdung were incorporated into the soil 7 days before planting and NPK fertilizer was applied at 2-3 weeks after planting. Data was collected on plant height, number of leaves, number of males and female flowers, number of fruits and weight of fruits at harvest. All the data collected were subjected to analysis of variance (ANOVA) and Duncan´s multiple range test (DMRT) was adopted in separating significantly difference means.

RESULTS:

Plant height

The result as presented in table 1 shows the effect of different Level of cow dung and NPK fertilizer on plant height of watermelon. The result revealed that, there was an increase in plant height in each of the treatments throughout the study period. Statistical analysis showed that there was a significant difference (P<0.05) at 2, 4, 6, 8 and 10 weeks after sowing in plant height. At 2 weeks after sowing, cowdung 2.5 t + NPK 150 kg/ha gave the tallest plants, while cowdung 10 t and NPK 150 kg/ha gave statistically same result. The control treatment at the other hand produced the shortest plants. At 4 weeks after sowing, the rate of 150 kg NPK/ha gave the tallest plants while treatment 2.5 tons +NPK 75 kg/ha and 1.25 tons +NPK 50 kg/ha has statistically the same heights. NPK 150 kg/ha gave the greatest mean height while cow dung 10 tons and cow dung 1.25 tons +NPK 50 kg/ha gave statistically the same height and control was found to be the least at 6 weeks after sowing. The treatment combination of cow dung’s 1.25 tons + NPK 50 kg/ha was observe statistically the highest plant at 8 weeks after sowing and control was least. Cow dung 10 kg/ha gave statistically the highest result at 10 weeks after sowing while cow dung 2.5 tons + NPK 75 kg/ha, cow dung 1.25 tons + NPK 50 kg/ha, cow dung 7.5 tons and NPK 100 kg/ha gave statistically the same heights, ranked second among the treatments and control was the least.

Table 1: Effect of Different Level of Cow dung and NPK Fertilizer on Plant height (cm) of watermelon

	Weeks After Sowing (WAS)
Treatments	2	4	6	8	10
Control	6.27^f	12.97^e	40.10^f	36.14^g	78.53^e
NPK 100 kg/ha	9.97^e	27.43^e	98.27^a	101^d	132^b
NPK 150 kg/ha	13.7^b	36.53^a	81.87^b	140^ab	119^bc
NPK 200 kg/ha	10.77^d	20.73^d	54.43^d	80.93^f	101^d
Cow dung 2.5 tons/ha	7.97^e	20.90^d	57.33^d	87.33^e	96.3^d
Cow dung 5.0 tons/ha	9.70^e	20.67^d	56.43^d	77.60^f	107^d
Cow dung 7.5 tons/ha	10.2^d	25.97^e	70.33^b	90.43^e	135^b
Cow dung 10.0 tons/ha	13.8^b	29.73^bc	96.13^ab	120^e	157^a
Cow dung 1.25 tons +NPK 50 kg/ha	12.37^bc	32.66^b	85.03^ab	140^a	153.8^b
Cow dung 2.5 tons +NPK 75 kg/ha	16.63^a	34.50^b	75.10^c	133.8^b	134^b
Cow dung 3.75 tons +NPK 100 kg/ha	11.87^c	20.63^d	46.43^e	105^d	101^d
LS	***	***	*	***	**
SE ±	1.008	1.663	13.753	2.113	18.219
Means in same column followed by the same letter are not significant different. LS= Level of significance, SE±=Standard Error, =Significant at 5%, =Significant at 1%, **=Significant at 0.01%.

Number of flowers:

The number of male and female flowers ware significantly affected by the different levels of treatment in table 2. The result of the treatment which shows, cow dung 1.25 t +NPK 50 kg/ha gave the highest mean number of male and females flowers per plants while NPK 150 kg/ha for male was found to ranks second and control was the least. Cow dung 10 t/ha, NPK 150 kg/ha NPK 100 kg/ha gave statistically the same number of female flowers per plant. A significant different was also observed in the percentage of female to male flowers in which cow dung 5 t/ha give the highest percentage of female flower.

Table 2: Effect of Different Levels of Cow dung, NPK fertilizer on Number of Male and Female flowers at 50% flowering of Watermelon

Treatments	Number of Male Flowers	Number of female flowers	Percentage of Female Flowers
Control	3.33^f	2.33^d	40.97^ab
NPK 100 kg/ha	8.00^c	3.67^ab	31.73^b
NPK 150 kg/ha	10.67^b	4.67^ab	30.73^b
NPK 200 kg/ha	5.33^d	3.00^c	36.80^ab
Cow dung 2.5 tons/ha	4.67^de	3.00^c	39.70^ab
Cow dung 5.0 tons/ha	4.33^e	3.33^b	43.40^a
Cow dung 7.5 tons/ha	6.67^d	4.00^b	38.40^ab
Cow dung 10.0 tons/h	8.33^c	4.67^ab	35.67^ab
Cow dung 1.25 tons +NPK 50 kg/ha	11.33^a	5.67^a	33.77^ab
Cow dung 2.5 tons +NPK 75 kg/ha	7.67^cd	4.00^b	34.20^ab
Cow dung 3.75 tons +NPK 100 kg/ha	7.00^d	3.69^b	35.00^ab
LS	***	**	*
SE ±	1.320	0.631	4.490

Means in same column followed by the same letter are not significant different. LS= Level of significance, SE±=Standard Error, *=Significant at 5%, **=Significant at 1%, ***=Significant at 0.01%.

The results obtain in table 3, shows statistically that there is no significant in number of fruits per plant. Cow dung 1.25 t + NPK 50 kg/ha observed to have highest number of fruits, cow dung 10 t/ha, NPK 150 kg/ha are statistically the same and ranks second. Average fruit weight statistically shows a significant different as affected by the application of different level of treatments. Do, cow dung 1.25 t/ha +NPK 50 kg/ha give the highest mean weight fruit per plant in which NPK 150 kg/ha ranks second. Furthermore, yield of watermelon per plots statistically shows a significant different between the treatments. cow dung 1.25 t + NPK 50 kg/ha ,cow dung 2.5 t +NPK 75 kg/ha and cow dung 10 t/ha statistically are the same but highest means was obtain under cow dung 1.25 t/ha +NPK 50 kg/ha (110.13) and the least was found to be control in all the treatments.

Yield parameter:

Table 3: Effect of Different Level of Cow dung, NPK Fertilizer on the Number of Fruits, Average Weight of and Yield per plot of Watermelon

	Number of Fruits/plant	Average Fruits Weight (kg)	Yield/plot (kg)
Control	1.67	1.23^e	17.07^c
NPK 100 kg/ha	3.00	3.33^c	78.43^ab
NPK 150 kg/ha	3.00	4.00^ab	96.80^ab
NPK 200 kg/ha	3.33	3.07^c	86.13^ab
Cow dung 2.5 tons/ha	2.33	2.20^d	39.20^b
Cow dung 5.0 tons/ha	2.33	2.37^d	41.87^b
Cow dung 7.5 tons/ha	3.67	3.17^c	92.80^ab
Cow dung 10.0 tons/h	3.67	3.73^b	109.07^a
Cow dung 1.25 tons +NPK 50 kg/ha	3.33	4.10^a	110.13^a
Cow dung 2.5 tons +NPK 75 kg/ha	3.67	3.50^b	101.87^a
Cow dung 3.75 tons +NPK 100 kg/ha	3.33	3.27^c	87.07^ab
LS	NS	***	***
SE ±		0.306	24.487
Means in same column followed by the same letter are not significant different. LS= Level of significance, SE±=Standard Error, ***=Significant at 0.01%, NS=Non Significant.

Total yield

Effects of different nutrient on the total yield of watermelon tons per hectare are present in table 4. A significant (p<0.01) different were observed among the treatments. The Combination of cow dung 2, 5 t/ha +NPK 75 kg/ha (50.93 t/ha), cow dung 1, 25 t/ha +NPK 50 kg/ha (55.07) and cow dung 10 t/ha (54.53 t/ha) were statistically the same. Highest yield was obtain by cow dung 1.25 t/ha +NPK 50 kg/ha and was able to increase yield of watermelon by 47 which is 85%, then followed by cow dung manure 10 t/ha with 46 increased in yield with 84%.

Table 4: Effect of Different Level of Cow dung, NPK Fertilizer on the total Yield per tons of Watermelon

	Yield/ha(tons) Deviations from control
		Tons/ha	%
Control	8.53^c	-	-
NPK 100 kg/ha	39.20^ab	30.67	78
NPK 150 kg/ha	48.40^ab	39.87	82
NPK 200 kg/ha	43.07^ab	34.54	80
Cow dung 2.5 tons/ha	19.93^b	11.4	57
Cow dung 5.0 tons/ha	20.93 ^b	12.4	59
Cow dung 7.5 tons/ha	46.40^ab	37.87	82
Cow dung 10.0 tons/h	54.53^a	46	84
Cow dung 1.25 tons +NPK 50 kg/ha	55.07^a	46.54	85
Cow dung 2.5 tons +NPK 75 kg/ha	50.93^a	42.4	83
Cow dung 3.75 tons +NPK 100 kg/ha	43.20^ab	34.67	80
LS	***
SE ±	12.24

Means in same column followed by the same letter are not significant different. LS= Level of significance, SE±=Standard Error, ***=Significant at 0.01%.

DISCUSSION:

The result of the study revealed that, growth and yield of water melon can be enhanced by the application of NPK fertilizer. The plant height was found to increase significantly with increasing level of NPK fertilizer (up to 200kg/ha) at 6WAS, this is inconformity with the result of Lawal (2000) and Agba et al (2005) who reported increase in growth and yield component of water melon in respond to increased level of fertilizer application. Similarly, Lawal (2000) reported that improved supply of nutrient to cucumber will lead to better utilization of carbon and subsequent synthesis of assimilate. The number of leaves increased significantly with fertilizer application at 4 and 6WAS, though statistically the same among the various levels used but significantly better than the control. This confirm the result of Abdel et al (2005) and Ahmed et al (2007) who reported increase in vine length and leaf number of water melon with increase in Nitrogen application. The study further revealed that, the number of flowers was also affected by the fertilizer application. This may be attributed to increase in vegetative growth as affected by fertilizer application. This is in accordance with the findings of Efediyi (2009) who reported a response of water melon flowering to fertilizer application. The result shows that, the application of cow dung has a significant effect on plant height. This is in conformity with the findings of Dean (2004), who reported that, vegetative growth and yield parameters shows a good responds to application of organic manure. It was also observed that, a significant difference exist on the number of fruits per plant with respect to application of cow dung. This is in line with the result of Walters et al (2000) who reported that, with increase in organic fertilizer, number of fruit per hectre increases. The result also revealed that, there is a significant interaction between the NPK fertilizer and various level of cow dung used. It was found that, the combination of Cow dung 1.25 tons +NPK 50 kg/ha gave the highest yield per hectare. This is in conformity with the findings of Borosic et al (2000) and Welters et al (2000), who reported that, there is an interaction between NPK fertilizer level and cow dung manure on the yield of water melon.

CONCLUSION:

Based on the result obtained, it should be concluded that the combination of 1.25 t cowdung/ha + 50 kg NPK/ha shows a significant increase in plant height, number of flowers, weight of fruits and final yield of Water melon in the study area. Considering the result of this findings, the combination of cow dung and NPK fertilizer at the rate of 1.25 t/ha + 50 kg/ha is recommended for farmers in the study area for profitable production of watermelon.

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Received on 18.12.2014 Accepted on 20.02.2015

Int. J. Tech. 5(1): Jan.-June 2015; Page 63-68