The experiment was conducted in the research field of the department of agroforestry and environment, Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU) from June 2009 to March 2011. The university is located in Gazipur district; 50 km away from the capital city Dhaka of Bangladesh. The study area belongs to the agro-ecological zone 28 i.e. the Madhupur tract which lies between 24.09o N latitude and 90.26o ’ E longitude with a mean elevation of 8.5 m above sea level (FAO/UNDP, 1988). The climate of the area is sub-tropical, characterized by a heavy rainfall during the period from July to September and scanty rainfall during the period of October to March. The premonsoon or hot season with scanty rainfall was observed from March to June. The soil of the experimental field was terrace soil, which is nearly equivalent to Ustocharepts suborder under the order Inceptisol of USDA Soil Taxonomy and belongs to the locally termed Salna Series of Shallow Red-Brown Terrace Soil (Brammer, 1971; Shaheed, 1984). The soil at the study site is silty clay loam in texture being acidic in nature, poor in fertility status, and impeded by internal drainage.
South-Western part. South-Eastern three rows of aonla were free from middle storied trees (no carambola and lemon). In North-Western side only carambola plants were planted just in the middle of the two aonla trees. Only lemon plants were planted in North western part of the orchard. The variety of aonla was local race, carambola was BARI Kamranga-1 and lemon was seedless BARI lebu. Three open pollinated cotton varieties (CB 9, CB 10 and CB 11) were tested in the alley of the aonla trees.
The research was done for the sustainable and productive aonla based multistoried agroforestry practices. With these aims in mind an aonla orchard was developed with middle storied tree species namely, carambola (Averrhoa carambola) and lemon plant (Citrus limon). Three cotton (Gossypium hirsutum) varieties were tested in two successive seasons in aonla orchard. At aonla based multistoried agroforestry system, aonla was used as the upper storied tree species and carambola and lemon were used as middle storied; cotton was the lower storied crop. The experiment was laid out in a two factors Randomized Complete Block Design (RCBD) with three replications. The plot size for each treatment was 6 m X 7 m. Adjacent plots were separated by 1 m distance and neighboring blocks were separated by aonla and middle storied trees. Open field was adjacent to the south of aonla orchard. The experiment consisted of two factors, which were: Factor A: Tree combinations T1 = Aonla only, T2 = Aonla + Middle storied tree species (Carambola and Lemon) and T3 = Open Field (control), factor B: cotton varieties were used for the study- Variety 1- CB 9, Variety 2 - CB 10 and Variety 3- CB 11.
Decomposed cow dung @ 5000 kg per ha was applied before land preparation. All chemical fertilizers were applied @ 92.2 kg per ha N, 34.5 kg per ha P, 125 kg per ha K, 18 kg per ha S, 7.3 kg per ha Zn, 3.4 kg per ha B and 9.5 kg per ha Mg in the form of urea, TSP, MoP, Gypsum, Zinc sulfate, Boric acid and Magnesium sulfate, respectively. Nitrogen was also applied at the rate of 92.2 kg per ha three times as side dressing 30, 50 and 75 day after sowing and also 125 kg per ha K was applied during third side dressing in the form of urea and MP respectively. Different necessary management practices were followed during the crop growing period. Gap filling was done at 7 and 10 DAS, respectively for getting optimum crop stand. Thinning was done twice 10 and 20 DAS, respectively. Three weeding were done at 20, 40 and 75 DAS. Earthing up was done at the time of last weeding (75 DAS). Insect and diseases were controlled by using insecticides and fungicides. Asataf 75 sp was applied @ 3 g/lit water at 30 and 45 DAS for controlling aphid and jassid. Mixture of Asataf 75 sp @ 3 g/ lit and Desis @ 2 ml/lit mixture were applied at 60, 75, 90, and 110 DAS to control aphid, jassid, bollworm and other lepidopteran larvae. Fungicide (Bevistine) was applied @ 2 g/lit water at 40 and 70 DAS to control fungal disease and boll rot, respectively.
Harvesting was done from the last week of December at an interval of 15 days. The yield of cotton genotypes was determined and converted to kg ha-1. After full maturation of bolls, seed cottons were collected by handpicking and they were dried under sunlight. Total three-hand pickings were done. After drying of seed cotton, lint and seed of cotton were separated by ginning. Cotton lint and seeds were weighed and lint was examined in the laboratory of Cotton Development Board, Khamarbari, Dhaka to analyze fiber quality. The performances of the cotton crop on various morphological, physiological; seed cotton yield and fiber quality parameters were analyzed using the statistical program of MSTAT–C to find out the statistical significance of the treatment effects. The means for all the treatments were calculated, and analysis of variance for all the characters was done. The mean differences among the treatments were evaluated by Duncan’s Multiple Range Test (DMRT) at a 1% and 5% level of significance (Gomez and Gomez, 1984).