Maize performance in a sandy loam ultisol amended with NPK 15-15-15 and poultry manure

Most of the soils in the tropics are known to be poor in fertility status and poor resource farmers do not often have the finance to procure adequate fertilizers needed for their crop. Hence, there is the need to supplement soil nutrients for optimal crop performance. A greenhouse study was carried out at the University of Nigeria, Nsukka to evaluate maize performance using different rates of poultry manure (PM) and NPK fertilizer. The treatments used were 400 kg/ha NPK fertilizer, 80 kg/ha NPK + 8 t/ha PM, 160 kg/ha NPK + 6 t/ha PM, 240 kg/ha NPK + 4 t/ha PM, 320 kg/ha NPK + 2 t/ha PM, 10 t/ha PM, and a control. The treatments had significant effect on dry matter yield, plant height and leaf area of the maize plant. Treatment 8 t/ha PM + 80 kg/ha NPK though was the best combination; there is need for a field evaluation of the trial to make proper recommendations for the optimal treatment application for maize production.


INTRODUCTION
Maize (Zea mays L.) is the third most important cereal crop in the world after wheat and rice with respect to area and productivity (Ranere et al., 2009).Maize is widely planted crop in most countries of the world and is among the most important common grain crop grown in Nigeria after rice.It has two growing seasons a year (early [March] and late [August] seasons).It is not only a source of food, feed but also utilized as a major ingredient of industrial product (Mohsin et al., 2012;Harris et al., 2007).
In the rainforest agro-ecology of southeastern Nigeria, intensive cropping has become more common and the primary function of soil productivity and fertility restoration has become less effective (Okigbo, 1989).However, bush fallow which had been an efficient, balanced and sustainable system for soil productivity and fertility restoration in the past is presently unsustainable due to high population pressure and other human activities which have resulted in reduced fallow period (Uwah et al., 2011).
Most of the soils in the tropics are known to be poor in fertility status (Okigbo, 1989); hence, there is the need to supplement the amount of nutrients for optimal crop performance.The poor fertility status is even more related to chemical than physical properties (Fernandez and Sanchez, 1990).Though the nutrients supplied by *Corresponding author.E-mail: benedictunagwu@yahoo.com.
Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License mineral fertilizers are usually specific and released rather fast, mineral fertilizer usually do not have significant residual effects after the year of application and have some times been reported to increase soil acidity and nutrient imbalance (Avery, 1995).
Complementary use of organic manures and mineral fertilizers has proved to be a very good management strategy in the tropics.It has a greater beneficial residual effect on the soil than that derived from the application of either inorganic fertilizers or organic manures.Eneji et al. (1997) reported that combined application of organic and inorganic fertilizers was the best for intercropping sweet potato and maize.Ayoola et al. (2008) in their work on the performance of high protein maize variety and soil nutrient changes with fortified organic fertilizer using municipal waste (MW) + cow dung (CD) at 5 t ha -1 , organic fertilizer + urea (that is, [2.5 t ha -1 MW + CD] + 100 kg ha -1 urea), inorganic NPK fertilizer and no fertilizer (control), reported significant (P = 0.05) increase in maize growth with treatment application.According to them, the unfertilized control plants had an average yield of 1.47 t ha -1 while yield (3.78 t ha -1 ) obtained from the organic fertilizer + urea was statistically the same with yield (3.70 t ha -1 ) got from inorganic fertilization.
Similarly, Satyanarayana et al. (2002) documented that application of farmyard manure at 10 t ha -1 and inorganic fertilizer at 120:60:45 kg N, P 2 O 5 and K 2 O ha -1 gave the highest rice grain yield which was 25% higher compared to no farmyard manure control.Also, Choudhary and Kumar (2013) reported that the growth, physiological parameters and yield attributes of maize were significantly influenced by the application of Vermicompost as compared to other organic fertilizer sources.According to IITA (1990) high and sustained crop yield can be obtained with judicious and balanced inorganic fertilization combined with organic manures.
Researchers have shown that complementary use of organic and inorganic fertilizers has proved a sound soil fertility restorative strategy in many countries of the world (Adeniyan and Ojeniyi, 2005;Unagwu et al., 2012).Much work on the complementary use of organic manures and mineral fertilizers has not been carried out in Nsukka series.The objective of this research was to determine the effects of combining different rates of organic and mineral fertilizer inputs on growth and dry matter yield of maize in Nsukka, southeastern Nigeria.

MATERIALS AND METHODS
A greenhouse experiment was carried out at University of Nigeria, Nsukka; located on latitude 06° 25'N and longitude 07° 24'E and is 400 m above sea level.Top soil samples (0-15 cm depth) were collected from the University Research Farm; air dried, crushed and sieved through 2 mm sieve.A 2 kg of the sieved soil was thoroughly mixed and poured into 28 perforated pots (85 cm 2 each) which were covered at the bottom with cotton wool to allow gradual water drainage.
Maize seed (var.Oba Super II) was planted two seeds per pot.The maize seedlings were later thinned to one per pot one week after germination.Inorganic fertilizer was applied as full application at three weeks after planting (WAP).Plant heights and leaf area were measured bi-weekly with measuring tape.Leaf area was estimated by multiplying the leaf length and the leaf width.Dry matter yield was determined on a balance after harvest by air drying for 3 days before oven drying to constant weight at 65°C.
The soil samples were analysed.Particle size determined using the Bouycous hydrometer method as described by Gee and Bauder (1986).Organic carbon was determined using Walkley and black dichromate method as described by Nelson and Sommer (1982).The percentage organic matter was obtained by multiplying the percentage of organic carbon content by the Van Bemmelen correction factor (1.724).Total N was determined by Kjeldahl method (Jackson, 1958).The exchangeable Na, K, Ca, Mg were extracted using ammonium acetate.Calcium and magnesium were determined by the Ethylene Diamine Tetraacetic Acid (EDTA) complexometric method.Sodium and potassium were determined by flame photometry.Available P was determined by Bray II method (Bray and Kurtz, 1945), soil pH was determined with a pH meter from a suspension soil: solution ratio of 1:25.Exchangeable acidity was gotten by titration method with NaOH.

Data analysis
The data obtained were subjected to the analysis of variance using GenStat software, 2003 Edition.Test of significance was done at 5% probability level.

RESULTS AND DISCUSSION
The chemical properties of the poultry manure used for the study is shown in Table 1.The poultry manure was alkaline (pH 9.5) and had high concentration of organic matter (47.41%) as well as high content of total N (2.83 g kg -1 ) and exchangeable bases.The physicochemical properties of the soil before the greenhouse trial are shown in Table 2.The soil is moderately acidic with a pH of 4.8.Texturally, the soil is a sandy loam with low values of organic matter (1.4%), total nitrogen (0.5 g kg - 1 ), low K + (0.07 g kg -1 ), Ca 2+ (1.3 g kg -1 ), Mg 2+ (0.8 g kg -1 ) and available P (9.7 mgkg -1 ).Due to the poor nutrient capacity of the soil and the usually high rainfall experienced in this zone, the application of inorganic fertilizers is usually lost to leaching (Agboola, 1998).Table 3 shows maize plant heights at different growth stages.Throughout the growing period, treatment T 2 (pots amended with 80 kg/ha NPK+ 8 t/ha PM) consistently had the tallest plants while treatment T 7 (control) consistently had the shortest plants.Plants grown in treatment T 1 to treatment T 6 were significantly (P < 0.05) taller than those grown in treatment T 7 (control).Although maize plant heights in treatment T 1 (400 kg/ha NPK fertilizer) amended pots were higher than those in treatment T 6 (10 t/ha PM) pots, both treatments showed statistically similarly plant heights.This could be due to the easily form of treatment T 1 for plant use.Maize heights recorded from treatment T 2 (80 kg/ha NPK + 8 t/ha PM) amended pots was significantly higher than that recorded from treatment T 1 amended pots by 29 and 20% at 2 and 4 WAP respectively.Also, maize height recorded from treatment T 2 (80 kg/ha NPK+ 8 t/ha PM) was significantly (p < 0.05) taller than that recorded from treatment T 6 (10 t/ha PM) by 20, 20.4 and 37.8% at 2, 4, and 6 weeks respectively.These results show that combine application of NPK fertilizer and poultry manure could have greater effect than sole application of either NPK fertilizer or poultry manure.This could be why maize performed better with the application of treatment T 2 (80 kg/ha NPK + 8 t/ha PM) compared to the application of either treatment T 6 (10 t/ha PM) or treatment T 1 (400 kg/ha NPK fertilizer).This result is in line with the findings of Murwira and Kurchman (1993) that nutrient use efficiency increased through the combination of manure and mineral fertilizer.
The effect of treatment application on the maize leaf area at different growth stages is shown in Table 4. Throughout the growing period, treatment T 7 (control) consistently had significantly (p < 0.05) lower leaf area compared with the other treatments while treatments T 2 (80 kg/ha NPK + 8 t/ha PM) consistently had significantly (p < 0.05) higher leaf area.
There was a significant (P < 0.05) effect on the maize dry matter yield with treatment application (Table 5).Among the treatments applied, treatment T 2 (80 kg/ha NPK + 8 t/ha PM) significantly (P < 0.05) had the highest dry matter yield (133.3 kg/ha) while treatment T 7 (control) had the least dry matter yield (35.4 kg/ha).This finding is

Table 1 .
Chemical properties of the poultry manure used for the experiment.

Table 2 .
Soil properties prior to the trials.

Table 3 .
Treatment effect on maize plant height during 2 to 6 WAP.

Table 4 .
Treatment effect on maize plant leaf area during 2 to 6 WAP.

Table 5 .
Mean treatments effects on dry matter yield at the end of greenhouse study.