Muhammad Aslam Ali
Department of Environmental Science, BangladeshAgricultural University, Mymensingh 2202, Bangladesh
M. A. Sattar
Department of Environmental Science, BangladeshAgricultural University, Mymensingh 2202, Bangladesh
M. Nazmul Islam
Department of Environmental Science, BangladeshAgricultural University, Mymensingh 2202, Bangladesh
K. Inubushi
Soil Science Lab., Graduate School of Horticulture, ChibaUniversity, Matsudo, Chiba 271-8510, Japan
Azolla, Cyanobacteria, Compost, Silicateslag, CH4flux, Paddy ecosystem
Crop-Soil-Water Management
Soil quality, Rice
The experiment was conducted in Bangladesh Agricultural University farm, Mymensingh, during the two consecutive rice growing seasons from December-May, 2010–2011 to December-May, 2011–2012. The experimental site was located 24.75° N latitude and 90.50° E longitude at an elevation of 18 m above sea level, under the Old Brahmaputra flood plain zone (Brammer et al.1988) (Agro-Ecological Zone-9, UNDP and FAO, 1988). The soil of the experimental field was clay loam with 1.78 % organic matter content, pH 5.9, available SiO2 58.5 mg kg−1, available P2O5 47.9 mg kg−1. The experimental field was a medium-high land and well-drained condition. Rice cultivar BRRI dhan29 was used as the test crop, which was developed by BRRI (Bangladesh Rice Research Institute). The experiment was laid out in a randomized complete block design (RCBD) with five treatments and three replications. Thus the total number of unit plots was 15. Each plot was separated by raising muddy and/ail from all sides. The effective area of each plot was 20 square meters (5 × 4 m). Between the blocks/replications, an irrigation sub-channel was constructed from where irrigation water was supplied to the plots. The sub-channel was connected with the main irrigation channel. The treatment combinations were randomly distributed to unit plots. The experimental treatments were: urea (220 kg ha−1) + rice straw compost incorporation (2 t ha−1) as a control (farmers practice), urea(170 kg ha−1) + rice straw compost incorporation(2 t ha−1) + silicate fertilizer (300 kg ha−1), urea(170 kg ha−1) + sesbania biomass incorporation(2 t ha−1) + silicate fertilizer (300 kg ha−1), urea(170 kg ha−1) + azolla biomass (2 t ha−1) incorporation+ cyanobacterial mixture (15 kg ha−1) inoculation in rice field + silicate fertilizer (300 kg ha−1);urea(170 kg ha−1) + silicate fertilizer (300 kg ha−1) + cattle manure compost incorporation (2 t ha−1). Well decomposed rice straw compost (2 t ha−1) and cattle manure compost (2 t ha−1) were uniformly spread over the experimental plots before flooding and incorporated immediately into the soil by harrowing.Sesbaniarostratawas grew in situ in the field and after 35 days above ground soft biomass (green leaves and soft twigs)was harvested and incorporated into the soil (2 t ha−1)1 day before rice transplanting. Azolla (2 t ha−1) was incorporated into field plots 1 day before rice transplanting. Cyanobacteria algal mixture (15 kg ha−1) was inoculated in field plots after 1 week of rice transplanting and allowed to grow with rice plant as a dual crop. The selected silicate fertilizer was in granular form, with pH 9.5 and was applied in the selected field plots 3 days before final land preparation and rice transplanting. The main components of the silicate fertilizer was CaO (41.8 %), SiO2(33.5 %), and Fe2O3 (5.4 %). The basal fertilizers triple superphosphate and muriate of potash (KCl) were applied according to the recommendation (P2O5:K2O=40:30Kgha−1) after the final land preparation and before rice transplanting. One-third of the recommended rate of nitrogenous urea fertilizer was applied before rice seedlings transplanting and the rest amount was applied through two equal splits at tillering stage (4 weeks after transplanting) and panicle initiation stage (6 weeks after transplanting). Twenty-one days old seedlings were transplanted in the main field at 25 × 20 cm row and hill spacing. Irrigation water was supplied in the rice field to keep the standing water level at around 5 cm during the transplanting to tillering stage, then 1-week drainage was followed at the productive tillering stage, thereafter, again flood water was maintained at 5 cm during the reproductive stage and intermittent flooding was followed during the grain filling stage. Finally, irrigation water was drained out from the plots 2 weeks before harvest to enhance the maturity of the crop.Soil physical and bio-chemical properties soil redox potential (Eh), water pH and dissolved oxygen concentration at the soil-flood water interface were measured every week interval by portable Eh meter (PRN-41, DKK-TOA Corporation), portable pH meter (Orion 3star, Thermo electron corporation) and portable DOMeter (Orion STAR A329, Thermo Scientific) respectively, during rice cultivation. Changes in the soil organic carbon content (Walkley and Black method; Allison1965) and labile organic carbon pool (0.333 M KMnO4 oxidation; Blair et al.1995), available silicate (1 M Na-acetate pH 4.0, UV spectrometer) and available phosphate(Molybdate blue colorimetry), ferrous iron (2 M Na-acetate solution;1,10 Phenanthroline method), exchange-able Ca2+, Mg2+, and K+(1 M NH4+-acetate pH 7.0, AA, Shimadzu 660) concentrations were determined through standard analytical methods. For mineral N measurements, 15 g fresh soils were extracted with 50 mL of1mol L–1 potassium chloride (KCl). Rice plant growth and yield characteristics Rice plant growth parameters and yield components were recorded from different treatment plots. Ten hills were selected at random from each unit plot excluding border rows to record the data on crop parameters. Yield components such as panicle number per hill, the number of grains per panicle, ripened grains, 1000 grain weight, harvest index and grain yield/unit area were determined at the harvesting stage.
Plant Soil (2014) 378:239–252
Journal