INTRODUCTION

The use of organic fertilizers is required for sustainable agriculture to supply nutrients, improve soil organic matter, soil physical, chemical properties, and soil productivity [1] since soil organic matter is the key to soil fertility and productivity. However, using organic manure such as farmyard manure, animal manure (cattle manure, poultry manure) serves a better option in substitute for chemical fertilizer. Animal manure is an important source of nitrogen (N) that provides nutritional needs of growing crops [2]. Nutrients contained in organic manures are released slowly and stored for a longer time in the soil, thereby ensuring a long residual effect [3]. Nitrogen (N) is typically the nutrient of most concern because it has a strong influence on cereal crop yields [4]. Mineralization and N recycling begin as soon as the manure is incorporated into the soil. The rate of mineralization however, varies with N sources, but the highest rate is at application and the rate decreases with time [4]. However, an understanding of N mineralization from organic manure is required to predict both the short and long-term release of N, and to avoid high levels of soil N accumulation that may be subjected to nitrate leaching and denitrification losses.

Maize (Zea mays L.) is the most important cereal worldwide. It occupied the third place among cereal crops in Nigeria [5], right after sorghum and millet. Appropriate nitrogen fertilization serves as the principal factor of nutrient management in high-yielding maize production systems [6]. It is also the nutrient element applied for most annual crops, which usually has significant effect on growth, development and yield of maize [7]. The performance of Nigeria agricultural sector in maize production has become abated over the decade due to some factors that militate against sufficient crop yields and fertilizer use [8]. In Nigeria, soil nutrient leaching and low level of soil organic matter have made nitrogen a limited nutrient to maize production [9, 10]. [11] reported that application of higher dose of N fertilizer enhance days to emergence, delayed days to tasseling and maturity, improved vegetative growth and grain yield of maize.

The disposal of large volumes of animal manure waste can be an expensive and environmentally threatening operation as this contributes to environmental problems such as greenhouse gas release and contamination of streams and ground water. However, creating innovative processes and pathways would allow this resource to be properly utilized and simultaneously reduce environmental impacts. The potential contamination of applying fresh animal manure waste cannot be overlooked thus making drying of animal manure waste an important process before usage. Dried livestock manures can be applied directly to crop fields either spread directly as this reduce field application costs by increasing bulk density, reducing volume and weed seeds content.

Several researches have been carried out on the application of sole animal manure neglecting other manure that cause environmental nuisance in our society. There is still lack of information on effects of animal manure mixture on dynamics of nitrogen forms hence the need for this study. The objectives of the study were to determine the (1) effect of animal manure mixture on ammonium nitrogen, nitrate nitrogen (2) synergistic effect of animal manure mixture on growth and yield of maize.

MATERIALS AND METHODS

Location of the Experiment, Soil Sample and Manure Collection

This study was conducted at the Federal University of Agriculture, Abeokuta, Ogun State, Nigeria situated between latitude 7°12′ N and longitude 3°20′ E. Soil samples (0–20 cm) were collected from four locations in Ogun state: Two locations from basement complex (Alabata and Osiele) and the other two from sedimentary parent materials (Itori and Papalanto). Soil samples from each location were bulked, air-dried and sieved with 2 mm mesh sieve. Three animal manures: poultry, goat and cattle manures were collected from the University farm, the Federal University of Agriculture Abeokuta. The manures were air-dried to constant weight after which they were grinded using porcelain mortar and pestle to reduce the particle size.

Soil and Manure Analysis

Sub samples from the soils were collected and analyzed as follow: Soil pH was determined in a soil water ratio of 1:2 using glass electrode attached to a pH meter [12]. Particle size analysis was determined using the hydrometer method [13]. Organic carbon content was determined using the wet-oxidation method [14]. Total nitrogen (N) was determined by Kjeldahl method after material digestion [15]. Exchangeable bases were extracted with 1 N ammonium acetate buffered at pH 7. Potassium and sodium in the extract were determined using flame photometer. Calcium and magnesium were determined using Atomic Absorption Spectrophotometer (AAS). Dried animal manures were digested with acids and analysed for organic carbon, total nitrogen and exchangeable bases, the pH and electrical conductivity (EC) of the dried manures were determined using distilled water according to standard procedures [16].

Nitrogen Forms Analysis

Ammonium nitrogen (\({\text{NH}}_{4}^{ + }\)–N) and Nitrate nitrogen (\({\text{NO}}_{3}^{ - }\)–N) were determined by extracting from 10 g soil using 20 ml of 1M potassium sulphate. The extracts were analyzed for \({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{3}^{ - }\)–N according to method described by [17].

Experimental Design

The experiment consisted of incubation study, screen house and field experiments. Incubation study and screen house experiment were laid out in complete randomised design while field experiment was laid out in randomized complete block design with five treatments and three replications. The treatments were control, cattle-goat manure mixture, cattle-poultry manure mixture, poultry-goat manure mixture and NPK 15:15:15 at 90 kg P ha–1. The combined manure mixtures at 90 kg P ha–1 were halved into two at an application rate of 45 kg P ha–1 for each manure (cattle, goat and poultry manure). However, the manure was mix at ratio 1 : 1.

Incubation

Four soils were used for this experiment; two soil each from basement complex (Alabata and Osiele) and sedimentary parent materials (Itori and Papalanto). One hundred grams of air-dried soil were dispensed into 200 g capacity plastics and treatments were applied. The incubation plastics used were labelled and each treated soil was thoroughly mixed and moistened with water to field capacity. Soil and manure mixture were incubated in dark cupboard for eight weeks at an ambient temperature of 27.5°C. Soil samples were taken at 0, 2, 4, 6 and 8 weeks of incubation and analysed for ammonium nitrogen (\({\text{NH}}_{4}^{ + }\)–N) and nitrate nitrogen (\({\text{NO}}_{3}^{ - }\)–N) according to the method as mentioned earlier.

Screen House Experiment

Based on the result of the incubation experiment, two soils were used for this study; one soil each from basement complex (Alabata) and Sedimentary parent material (Papalanto). Five kilogrammes of soil sample were dispensed into perforated 7 kg capacity containers with saucers placed under to avoid nutrient leaching. Dried manure mixtures were applied 2 weeks before planting while NPK fertilizers were applied 2 weeks after planting. Maize seeds (BR-9928-DMR-S-Y) were sown at 3 seeds per pot and thinned to one plant per pot at two weeks after planting. Soil samples were taken at 0, 2, 4, 6 and 7 weeks from containers and analysed for \({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{3}^{ - }\)–N, maize agronomic parameter (plant height, stem girth) were measured at 2, 4, 6 and 7 weeks after planting. Similar procedure was carried out for another 6 weeks for the second cycle of maize growth though soil samples and agronomic data were only collected at 4 and 6 weeks after planting.

Field Experiment

One soil of the two soils from screen house experiment was used for the field experiment. Soil from Alabata which belonged to basement complex parent material was chosen for the field experiment, although the field location (FUNAAB) was used since it was analyzed as a separate soil based on the fact that soils characteristics usually vary with distance. The field experiment was carried out at the Directorate of teaching and research farm, the Federal University of Agriculture, Abeokuta. The field was cleared mechanically with tractor, ploughed and harrowed. Dried manure mixtures were applied 2 weeks before planting by spreading on the field manually while NPK fertilizers were applied 2 weeks after planting. Maize seeds (BR-9928-DMR-SR-Y) were sown at a spacing of 0.25 by 0.75 m. Maize plants that were representative of each plot were tagged within the net plot, plant height and stem girth of tagged plant were measured with meter ruler and venier calliper at 2, 4, 6, 8 and 10 weeks after planting, respectively. At 2, 4, 6, 8 and 10 weeks, soil samples were also taken and analysed for nitrogen forms. At 12 weeks after planting, maize shoot (above ground portion) from net plot was harvested, dried in an oven at 65°C to constant weight. Data on dry shoot weight were recorded.

Statistical Analysis

Experimental data for all parameters of treatment effects were analyzed using a one-way ANOVA implemented in PROC ANOVA in SAS [18] followed by mean comparisons using Duncan multiple range test at 5% level of probability.

RESULTS

Pre-Cropping Analysis of the Soil Samples

Some of the properties of soils used for the study are presented in Table 1. All the soils except soil from Papalanto were loamy sand. The pH of the soils varied from neutral to alkaline. The organic carbon and magnesium content of the soils was the lowest and highest in soils form Itori and Osiele, respectively. The highest total N was obtained in soil from Itori while the least value was found in soil from FUNAAB. There was variation in exchangeable cation. It was observed that soil from Papalanto had the least of Ca, K and Na while the highest value was recorded in FUNAAB.

Table 1.   Physical and Chemical properties of soils
Full size table

Characterization of Animal Manure Amendments

The pH of the manures ranged from 8.20 in poultry manure to 9.60 in goat manure (Table 2). The total nitrogen content of the manures ranged from 3.20 g kg–1 to 3.60 g kg–1. The order of organic carbon was goat manure > poultry manure > cattle manure while the carbon:nitrogen ratio was in the order of cattle manure > goat manure > poultry manure. Poultry manure was significantly higher in calcium when compared to other manures. The magnesium content was significantly higher in poultry manure, followed by goat manure and cattle manure. The order of sodium and potassium content of the manures were goat manure > poultry manure > cattle manure.

Table 2.   Characterization of animal manure
Full size table

Soil \(NH_{4}^{ + }\)–N and \(NO_{3}^{ - }\)–N Content of Unamended and Amended Soils in Incubation Experiment

Significant difference (P ≤ 0.05) was observed in the mineral N (\({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{3}^{ - }\)–N) with different treatment applied across the weeks (Table 3). A significant increase in \({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{3}^{ - }\)–N was observed in soil from Alabata. \({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{3}^{ - }\)–N increased from 2nd to 4th WAI (weeks after incubation) and decrease from 6th WAI to 8th WAI. Co-application of cattle-goat manure mixtures gave the highest value at 4th week for both \({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{3}^{ - }\)–N (207.20 mg N kg–1 and 69.52 mg N kg–1), respectively and the least value of \({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{3}^{ - }\)–N was observed with the application of NPK at 8th WAI. Similar trend was observed in soil from Osiele with \({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{3}^{ - }\)–N increasing from 2nd to 4th WAI and decreasing from 6th to 8th WAI. The application of poultry-goat manure mixture resulted in the highest value of \({\text{NH}}_{4}^{ + }\)–N (212.15 mg N kg–1) at 6th WAI and \({\text{NO}}_{3}^{ - }\)–N (98.23 mg N kg–1) at 4th WAI. The \({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{3}^{ - }\)–N in soil from Itori with the application of amendment significantly differed when compared with control at the 0th WAI of incorporation. \({\text{NH}}_{4}^{ + }\)–N decreased at 2nd WAI, increased at 4th WAI, decreased at 6th WAI and finally increased at 8th WAI while \({\text{NO}}_{3}^{ - }\)–N increased from 2nd to 6th WAI and later decreased at 8th WAI. Cattle-goat manure mixture gave the highest value in \({\text{NH}}_{4}^{ + }\)–N (188.51 mg N kg–1) at 4th WAI and \({\text{NO}}_{3}^{ - }\)–N (67.83 mg N kg–1) at 6th WAI. The least value in \({\text{NH}}_{4}^{ + }\)–N (100.38 mg N kg–1) and \({\text{NO}}_{3}^{ - }\)–N (10.74 mg N kg–1) was observed at 8th week with the application of NPK. Similar trend was observed in soil from Papalanto.

Table 3.   Effect of animal manure mixture on soil \({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{3}^{ - }\)–N in incubation study
Full size table

Table 4 shows that application of manure mixture produced higher amount of \({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{3}^{ - }\)–N in soil compared to NPK fertilizer and control in cycle 1 and 2. \({\text{NH}}_{4}^{ + }\)–N in soil from Alabata decreased significantly at 4th and 7th WAP (weeks after planting) in the first cycle while significant increase in \({\text{NH}}_{4}^{ + }\)–N was observed in second cycle at 4th and 6th WAP. The least amount of \({\text{NH}}_{4}^{ + }\)–N was observed in NPK treatment for both cycles. The application of amendment also had significant effect on \({\text{NO}}_{3}^{ - }\)–N of soil from Alabata in both cycles. \({\text{NO}}_{3}^{ - }\)–N increased at 4th WAP and decreased at 7th WAP in cycle1, similar trend was also observed in cycle 2. The highest value of \({\text{NO}}_{3}^{ - }\)–N was recorded as 165.39 mg N kg–1 and 64.13 mg N kg–1 with application of cattle-poultry manure mixture in cycle 1 and cycle 2 respectively while the least value was observed in NPK amended soil. Treatment application had a significant effect on soil from Papalanto. \({\text{NH}}_{4}^{ + }\)–N in cycle 1 decreased at 4th WAP and increased at 7th WAP. The highest \({\text{NH}}_{4}^{ + }\)–N was observed with poultry-goat manure mixture (250.62 mg N kg–1) at 6th week after planting. Similar trend was observed in cycle 2. A significant increase in \({\text{NO}}_{3}^{ - }\)–N was observed at 4th WAP while a decrease was recorded at 7th WAP. Poultry—goat manure amended soil had the highest \({\text{NO}}_{3}^{ - }\)–N value at 4WAP while the least value of \({\text{NO}}_{3}^{ - }\)–N was recorded in NPK amended soil at 7 WAP. Similar trend was observed for \({\text{NO}}_{3}^{ - }\)–N in cycle 2. Comparing both cycle in the screen house experiment based on the treatment applied, Soil from Alabata had significantly higher amount of \({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{3}^{ - }\)–N than soil from Papalanto. It was observed that poultry-goat manure and cattle-goat manure had positive effect at increasing the \({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{3}^{ - }\)–N. The values observed were higher with poultry-goat manure mixtures in comparison with other manure mixtures in both cycles.

Table 4. Effects of animal manures mixture on \({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{3}^{ - }\)–N of soils in screen house experiment for two cycles
Full size table

Application of animal manure mixture had significant effect on \({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{3}^{ - }\)–N in the field experiment (Table 5). An increase in the value of \({\text{NH}}_{4}^{ + }\)–N from 2nd WAP till 6th WAP, decrease at 8th WAP and final increase at 10th WAP was observed with the addition of manure amendment and NPK fertilizer. The highest concentration of \({\text{NH}}_{4}^{ + }\)–N was recorded with the application of cattle-poultry manure mixture (171.48 mg N kg–1) at 8th week and the least value was obtained in NPK amended soil as 95.63 mg N kg–1. \({\text{NO}}_{3}^{ - }\)–N significantly increased at 4th WAP, decreased at 6th WAP and later increased from 8th to 10th WAP. The highest value of \({\text{NO}}_{3}^{ - }\)–N was recorded with cattle-poultry manure mixture (96.98 mg N kg–1) at 4th WAP and the least value was obtained for NPK (20.05 mg N kg–1) at 6th WAP.

Table 5.   Effects of animal manures mixture on soil \({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{3}^{ - }\)–N in field experiment for ten weeks
Full size table

Effect of Animal Manure Mixture on Plant Height and Stem Girth of Maize

Table 6 shows that a significant increase was recorded at 7th week when compared with 4th week for plant height. At 4th week, plant height gave the highest value with the application of poultry-goat manure followed by cattle-poultry manure and cattle-goat manure. Manure amendments increased increase the plant height than in NPK and control. Similar trend was observed at 7th week except that the highest value was observed in cattle-goat manure and cattle-poultry manure (113.33 cm). Significant increased was observed in the second cycle of the experiment for soil from Alabata. At 4th week, plant height increased significantly across the manure mixture applied. However, in the first and second cycles in soil from Papalanto, significant difference was observed across the weeks and within the treatment. At 4th week, plant height gave the highest value with manure amendments in comparison with the control and NPK. Similar trend was observed at 7th week, the order of increase was cattle-goat manure > poultry-goat manure > cattle-poultry manure > NPK > control. The highest value of plant height was recorded in soil amended with cattle-goat manure at 4th week and 7th week (52.00 cm) and (126.33 cm) respectively with the least value observed in NPK.

Table 6.   Effects of animal manures mixture on plant height of maize in screen house experiment for two cycles of two soils
Full size table

Effect of treatment application on stem girth in soil from Alabata was not significant throughout the planting week in first cycle (Table 6). In the second cycle, stem girth was significantly different across the weeks and within the treatment applied at 6th week. Effect of treatment application in soil from Papalanto led to significant increase in stem girth in first cycle. At 4th week, increase was observed across the treatment used, with cattle-goat manure resulting in highest value (0.70 cm). At 7th week, increase was observed in different treatment used over control with the highest value obtained with co-application of cattle and goat manure (0.90 cm). For the second cycle, stem girth was significantly different across the weeks and within the treatment applied. Increase was observed in the treatments applied at 4th week with the highest value obtained with cattle-poultry manure mixture (0.25 cm).

The result showed the effect of animal manure mixture application and NPK fertilizer on plant height and stem girth of maize in field experiment on Table 7. There was no significant difference in plant height during the experiment. At 2nd week, the plant height obtained with cattle poultry manure was higher than poultry-goat manure followed by cattle-goat manure. Increase in plant height was observed at the 4th weeks in comparison to the 2nd week. There was continuing increase in plant height from 6th week to the 10th week. The stem girth of maize did not differ within treatment from 2nd week to 8th week. At 2nd week, the stem girth obtained with poultry-goat manure was higher than cattle-poultry manure followed by cattle-goat manure, NPK and control. At the 10th week, application of cattle-poultry manure significantly increased the stem girth than other manure amendments, NPK and control. Shoot dry weight of maize grown in screen house experiment on soil from Alabata did not differ in the first cycle (Table 8). Shoot dry weight of maize across the treatment in the second cycle was greater with cattle-goat manure while the least was recorded with NPK. Significant difference (P ≤ 0.05) in shoot dry weight was observed in both cycle of screen house study for papalanto soil. Significant increase in shoot dry weight across the treatment applied in first cycle and second cycle was recorded. Cattle-goat manure gave the highest value in shoot dry weight for both cycles though the value did was similar to those recorded with the application of cattle-poultry manure and poultry-goat manure. Comparing the two cycles, shoot dry weight was heavier in the first cycle than the second cycle.

Table 7.   Effects of animal manures mixture on plant height and stem girth of maize in field experiment for ten weeks
Full size table
Table 8. Effect of animal manures mixture on shoot dry weight of maize in screen house and field experiments
Full size table

There was no significant difference (P ≤ 0.05) observed in shoot dry weight across the treatment applied in field experiment. Cattle-poultry manure had the highest value, while the control had the least according to the treatment applied. The trend of increase for shoot dry weight for the amendments were cattle-poultry manure > cattle-goat manure > poultry-goat manure > NPK > control.

DISCUSSION

Result of pre cropping soil analysis showed that the soils varied in physicochemical properties. The soils have low natural fertility due to nutrient depletion resulting from continuous cultivation of the soil. Major constraint in crop production in south western Nigeria and indeed the tropics have been identified as having problems relating to nutrient deficiencies and imbalances as reported by [19]. The soils were loamy sand to sandy. They were generally low in nutrient content and hence would respond to nutrient application making them suitable for the study. The low nutrient status of most of these soils were similar to observations of [20] who reported that low nutrient status of most tropical soils necessitates the use of fertilizers for intensive cultivation, since they are not able to support sustainable crop production over a long time.

The pH of the pure poultry manure was considered moderately alkaline, while that of pure cattle and goat manure was strongly alkaline [21]. The alkaline pH in the three manures indicates the presence of basic cations at the expense of acidic ones. This would allow for nutrients availability in the soil after mineralization. The variation in manure nutrient content is an indication that manure quality varies in relation to animal type, age, diet and management system as reported by [22]. Goat manure is richer in organic carbon, sodium and potassium while poultry manure is richer in calcium and magnesium. The high content of calcium and magnesium in poultry manure could be as result of calcium and magnesium salts which are specifically added to poultry diets for body osmotic balance, building of bones and egg production (for layers). This is in agreement with the findings of [16] who observed that Ca and Mg content of poultry litter was seen to be significantly higher than other manures. The high sodium content of goat manure shows that application of this manure to soils should be done with caution, in order to avoid the problem of soil salinity; the salt content of application rates of goat manure should be considered especially when it is to be applied to non-tolerant crops. The C/N ratios of the manures are potential indicators of faster mineralization and high nutrient availability. Similar results were observed from previous research by some authors [22, 23] that poultry manure is expected to mineralize faster compare to goat manure and cattle manure. [16] also reported that immobilization of applied nutrients is likely to occur in cattle and goat manure when compared to poultry manure because of their higher C:N ratios.

The changes in nutrient release patterns during the first few weeks after applying organic amendments are important since it has implications on crop growth. The type of amendment added differently affected the nutrient releasing pattern from amended soils in the study. This rapid rise of \({\text{NH}}_{4}^{ + }\)–N content is attributable to the decomposition of the easily decomposable nitrogenous substances present in the organic materials. The application of cattle-goat manure mixture (CGM) produced the highest amount of mineral N in soil from Alabata and Papalanto, in which increase was observed in the \({\text{NH}}_{4}^{ + }\)–N across the incubation weeks with the application of poultry goat manure. The manure treatments significantly increased \({\text{NH}}_{4}^{ + }\)–N over the control treatment. The differences in N mineralization among the manures studied were larger as expected from their initial characterization. Manure amendment added a sharp decline in soil N mineralization after 8th weeks of field experiment. Subsequently, there was a gradual increase in N mineralization as it reaches the end of the field experiment. Adding manure amendment to soil is sometimes followed by an extended period where N immobilization limits N availability [24]. Other workers have found that laboratory incubations of manure soil lasting for weeks may result in negative N mineralization values [25], while longer incubations resulted in positive values [26]. Comparing the incubation weeks, \({\text{NO}}_{3}^{ - }\)–N increased at 2nd week and later decreased at 4th week while increase was also observed at 6th week, decreased at 8th week. The result indicated that application of treatment significantly increased and later decreased \({\text{NO}}_{3}^{ - }\)–N mineralization content at different weeks of incubation. Increase in the concentration of \({\text{NO}}_{3}^{ - }\)–N was observed with the treatments after incubation as a result of the activity of nitrifying bacteria which converts \({\text{NH}}_{4}^{ + }\)–N into \({\text{NO}}_{3}^{ - }\)–N. It was observed from the study that the amount of \({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{3}^{ - }\)–N mineralized significantly differed among the treatments. On average, the effect of cattle-goat manure was seen to cause the increase in \({\text{NO}}_{3}^{ - }\)–N in incubation study, poultry-goat manure in screen house and cattle-poultry manure in field experiment study. [27] reported that the mineralization of N is influenced by incubation period, moisture regime, type of soil and the rate of organic materials applied.

Considering plant height, it was observed that cattle poultry manure treatment increased plant height, compared to other manure amendment and control. These responses may be attributed to its high content of nitrogen, phosphorus and potassium [28]. Another explanation might be due to the effect of poultry manure on soil fertility (poultry manure restored soil fertility). On the other hand, [29] reported that poultry litter contains, a considerable amount of organic matter, hence have an impact on soil pH and liming due to varying amount of calcium carbonate in poultry feed. The source of nitrogen from poultry manure resulted in taller plants because nitrogen was found to increase plant height. This is agreement with [30] who reported that chicken manure fertilizer significantly increased plant height. The increase in vegetative growth parameters such as plant height, stem girth and others resulted from improved soil nutrient, as a result of animal manure mixture (cattle poultry manure). [31] reported that nitrogen and phosphorus uptake, as a function of chicken manure application rate, increased progressively with increasing manure rates.

Stem girth of maize was highest with the application of cattle poultry manure in the field experiment even though no manure amendment differed from each other. This could be attributed to losses of plant available nitrogen making all the manure amendment to behave the same way. The experiment studied showed that manure mixture ratio 1:1 gave good maize growth and performance. This was an indication of higher availability of nutrients from poultry manure, relative to other manure and NPK. All manures and NPK used in the study showed that six weeks is the optimum for peak of growth. By eight weeks, growth was marginal. This means that nutrients from applied manure amendment must be available for plant growth by the sixth week.

CONCLUSIONS

The findings in this study showed that manure amendment increased chemical properties of the soil and agronomic performance of maize. An increase in \({\text{NH}}_{4}^{ + }\)–N and \({\text{NO}}_{3}^{ - }\)–N was observed from the 2nd week to the 4th week after incorporation in incubation experiment. Application of poultry-goat manure and cattle-poultry manure had significant effect on increasing soil nitrate nitrogen and ammonium nitrogen in screen house and field experiments, respectively. Cattle-poultry manure mixture had interacting effect on agronomic performance of maize. Therefore, the inclusion of poultry manure is recommended for use in manure mixture.