INFLUENCE OF PIG MANURE , UREA AND COMBINATIONS OF THEIR REDUCED LEVELS ON THE PERFORMANCE OF AMARANTHUS CRUENTUS IN A RAIN 0 FOREST ULTISOL

The influence of sole and combined application of pig manure and urea on the performance of Amaranthus cruentus at Umudike in a rainforest Ultisol was investigated for two years. The study was laid out in a randomized complete block design with four replications. There were six treatments consisting of pig manure applied at 90 kg N/ha (full dose of manure), urea applied at 60 kg N/ha (full dose of urea), 1⁄2 dose of manure (45 kg N/ha) + 1⁄2 dose of urea (30 kg N/ha), 1⁄4 dose of manure (22.5 kg N/ha) + 3⁄4 dose of dose of dose of urea (45 kg N/ha), 3⁄4dose of manure (67.5 kg N/ha) + 1⁄4 dose of urea (15 kg N/ha), and control (no manure, no urea). Amaranthus height was not significantly affected by the treatments when compared with the control, though the tallest plant height of 76.30 cm was obtained from the combination of 1⁄2 manure + 1⁄2 urea treatments. The overall results showed that the combination, 1⁄2 manure + 1⁄2 urea (i.e. 45 kg N/ha of pig manure + 30 kg N/ha of urea) gave significant (P < 0.05) increases in stem girth (17.42), number of leaves per plant (44.76), fresh yield (41.51 t/ha) and in the dry matter yield (3.49 t/ha) of Amaranthus than sole application of either of them, and is therefore recommended as the best for optimum production of Amaranthus in the study area.


INTRODUCTION
The maintenance of soil fertility is essential in achieving and sustaining high crop yields over a period of time.Use of inorganic fertilizers has proven to be more convenient and impactful than the use of organic fertilizers, but the resulting soil physical degradation, increased soil acidity and soil nutrient imbalance have drawn the attention of researchers back to the use of organic manure.Application of organic materials as fertilizers provides growthregulating substances and improves the physical, chemical and microbial properties of the soil (Belay et al., 2001).Sole use of organic fertilizers to sustain cropping has, however, been reported to be inadequate, as they are required in rather large quantities to meet crops' nutrient requirements because of their relatively low nutrient content (Palm et al., 1997).
It has been reported by several researchers (Satyanarayana et al., 2002;Adeniyan and Ojeniyi, 2005;Obasi et al., 2006) that high and sustainable crop yields are only possible with integrated use of inorganic fertilizers with organic manure.Complementary application of inorganic and organic fertilizers increases nutrient availability and reduces losses by converting inorganic nitrogen into organic forms (Chand et al., 2006;Chen, 2008).It enhances the efficiency of the fertilizers and also reduces environmental problems that may arise from their use (Zublena et al., 1996;Hoffman et al., 2001).
This research was therefore, conducted to determine the combined effects of inorganic and organic fertilizers on the performance of Amaranthus and also to know the best combination of inorganic and organic fertilizers for Amaranthus production in a rainforest ultisol.

MATERIALS AND METHODS
The experiments were conducted at the Research Farm of Michael Okpara University of Agriculture, Umudike to determine the combined effects of organic and inorganic fertilizers on the performance of Amaranthus and also to establish the best combination of DOI : http://dx.doi.org/10.4314/as.v12i1.4organic and inorganic fertilizers for Amaranthus production for two consecutive years.
The experimental design used was a randomized complete block design.The experimental area in each cropping season was slashed manually, ploughed and harrowed mechanically while the field was manually marked out with pegs.Flat beds were also manually made using a spade.Each plot measured 3 m x 1.5 m (4.5 m 2 ).An alley of 1.2 m was left between blocks and 0.6 m between plots.
The various rates of pig manure were applied one week before planting (1 WBP) by broadcast with incorporation method, while urea fertilizer treatments were applied two weeks after planting (2 WAP) by band placement method.Amaranthus seeds were mixed with dried river sand first before sowing so as to ensure that the seeds were not planted too close together for proper management of the seed rate desired.The mixture was about 70 % sand and 30 % Amaranthus seeds.These were evenly distributed directly on drills at a distance of 10 cm between each row.The seedlings were later thinned down to one plant per stand few days after emergence at a spacing of 10 cm between plants.Therefore, the planting distance was 10 cm x 10 cm giving a plant population of 450 plants per bed (450/4.5 m 2 ) and 1,000,000 plants per hectare.The plots were kept weed free throughout the crop growing period by hand pulling because of the closeness of the plants.Plots were irrigated manually using watering cans before planting and immediately after planting to ensure and enhance sprouting.Watering was done 2 times a day (morning and evening) at the initial stage of development, and was reduced to once (evening only) every day at the later stage.During this time there was a good canopy development that shaded the ground and reduced soil moisture loss.

Agronomic
parameters measured included plant height (cm), number of leaves per plant, stem girth, fresh yield and dry matter yield (kg/ha). Plant height was measured with a meter rule as the height from the base of the crop (ground level) to the tip of ten tagged plants, while the number of leaves was taken by counting the fully opened leaves per plant.These measurements commenced 3 WAP and continued at weekly interval until the end of the experiment.Harvesting was done at 5 WAP by uprooting the entire plant from an area of 100 cm x 100 cm per plot and the fresh yield determined after rinsing the roots free of sand.For dry matter determination, the ten tagged plants were uprooted, rinsed, and oven-dried at 65 0 C to constant weight (Maerere et al., 2001) and the weight determined.Stem girth was measured at harvest using a venier calliper.The data collected were subjected to analysis of variance (ANOVA) using the general linear models (GLM) procedures of the Statistical Analysis Systems programme (SAS, 1989) to determine treatment effects.Means were separated using the Fisher's Least Significant Difference (FLSD) at 5 % level of probability.

Growth parameters
Plant height of Amaranthus was not significantly affected by the sole and combined use of pig manure and urea in the first and second cropping seasons as indicated in Table 1, although the tallest plant of 76.30 cm (5 WAP) was obtained from the ½ manure + ½ urea treatment .There was no significant difference in the number of leaves per plant at 3 WAP from either the sole or combined use of the treatments in the first and second cropping seasons as presented in Table 2, but the treatments significantly increased the number of leaves per plant relative to the control at 4 and 5 WAP.The highest number of leaves per plant was obtained from the ½ manure + ½ urea treatment combinations.The highest stem girth value of 17.42 was also obtained from the ½ manure + ½ urea treatment (Table 3).Generally, the best result was obtained from combined use of organic and inorganic fertilizers.This supports the findings of Akande et al. (1998) and Adediran et al. (2005) indicating a better effect of organic materials on Amaranthus when applied in combination with inorganic fertilizer.