M. Ashrafuzzaman

Planting time and mulching effect on onion development and seed production

A field experiment was conducted to evaluate effects of planting time and mulches on bulb growth and seed production of onion (Allium cepa L.) cv. Taherpuri. Planting time and mulches had significant influence on almost all parameters studied. Onion planted on 21 November had better agronomic traits contributing towards yield formation. Growth and seed production was accelerated by black polythene. Seed yield (460.81 kgha-1) was highest in the plots planted on 21 Nov. Seed yield was 529.06 kgha-1 where black polythene mulch was used.

Effect of plastic mulch on growth and yield of chilli (Capsicum annuum L.)

In this work a field study was conducted to evaluate the effect of coloured plastic mulch on growth and yield of chilli from October 2005 to April 2006. The plastic mulches were transparent, blue, and black and bare soil was the control. Different mulches generated higher soil temperature and soil moisture under mulch over the control. Transparent and blue plastic mulches encouraged weed population which were suppressed under black plastic. Plant height, number of primary branches, stem base diameter, number of leaves and yield were better for the plants on plastic. At the mature green stage, fruits had the highest vitamin-C content on the black plastic. Mulching produced the fruits with the highest chlorophyll-a, chlorophyll-b and total chlorophyll contents and also increased the number of fruits per plant and yield. However, mulching did not affect the length and diameter of the fruits and number of seeds per fruit. Plants on black plastic mulch had the maximum number of fruits and highest yield. Thus, mulching appears to be a viable tool to increase the chilli production under tropical conditions.

Biomass accumulation and energy conversion efficiency in aromatic rice genotypes.

A field experiment was conducted to evaluate photosynthetic efficiency along with different growth parameters of aromatic rice genotypes. Forty genotypes including three non-aromatic checks exhibited enormous variations for leaf area index (LAI), crop growth rate (CGR), relative growth rate (RGR), net assimilation rate (NAR), grain yield, total dry matter, harvest index and photosynthetic efficiency or energy use efficiency (Emu) at panicle initiation and heading stages. Minimum LAI-value was 0.52 in Khazar at PI stage and maximum was 4.91 in Sakkor khora at heading stage. The CGR-value was in the range of 4.80-24.11 g m(-2) per day. The best yielder BR39 produced grain of 4.21 t ha(-1) and the worst yielder Khazar gave 1.42 t ha(-1). Total dry matter (TDM) yield varied from 4.04 to 12.26 t ha(-1) where genotypes proved their energy use efficiency a range between 0.58 to 1.65%. Emu showed a significant positive relation with TDM (r=0.80(**)), CGR (r=0.72(**)) and grain yield (r=0.66(**)). A negative correlation was established between TDM and harvest index and LAI and RGR. Path analysis result showed that NAR at heading stage exerted highest positive direct effect (0.70) on Emu.

Role of Accumulated Calcium in Alleviating Aluminum Injury in Wheat Plants

Aluminum (Al) sensitive wheat cultivar kalyansona was grown for 14 d in a range of Ca solution (125, 625, and 2500 μM) plus other nutrients without Al. At 14 d after Ca treatment, half of these plants were harvested (H1), and the rest of the plants were exposed to 100 μM Al for additional 6 d and harvested (H2). Severe Al injury was found only in the plants with the lowest supply of Ca before Al treatment. Aluminum concentration in the apoplastic fluid was very high at 125 μM Ca probably because the plasma membrane of some of the cells was destroyed due to the attack of 100 μM Al. Aluminum content in roots decreased with increasing supply of Ca before Al treatment. Calcium content decreased drastically at harvest (H2) in the plants with 100 μM Al. Under Al stress conditions, the plant responded to Al in different ways due to not only the different Ca supply but also the variation of Ca content in the plant tissues. Actually, the plants having the largest Ca content in the roots before Al treatment can receive less Al injury during Al treatment. To substantiate this idea, a companion study was conducted to investigate the effects of 2500 μM Ca supply during, before, and after 100 μM Al treatment on root growth. The results indicated clearly that exogenous Ca supply before Al treatment is able to alleviate Al injury but less effective than Ca supply during Al treatment.

Improvement of yield potential of rice through combined application of biofertilizer and chemical nitrogen

A field experiment was conducted to evaluate the su itable combination of plant growth promoting rhizobacteria ( Azospirillum biofertilizer strain BM9 and BM11) along with diff erent nitrogenous fertilizer levels (0, 20, 40, 60, 80 and 100% N) on rice varie ty Binadhan 4 at Bangladesh Institute of Nuclear Agriculture farm, Mymensingh in Aman season of 2006 . Roots of rice seedlings were dipped in broth culture of bacterial strains in Luria-Bertani (LB) medium for half an hour before transplanting. Data were recorded on plant growth, yield, yield components a nd nutrient uptake. Results showed a significant increase in growth parameter like plant height, sho ot dry weight, root length and dry weights, grain a nd straw yields, effective tillers/hill and panicle le ngth, and nitrogen, phosphorus and potassium uptake over uninoculated under most nitrogen levels except 100% N. Number of grains per panicle and 1000 grain weights were increased considerably compared to uninoculated control. Strains BM9 and BM 11 along with 80% N produced similar grain and straw y ield to that with 100% nitrogen fertilizer applied alone. Results revealed greater scope of Azospirillum biofertilizer application for supplementing fertil izer nitrogen for achieving optimum yield of rice in Ban gladesh soil and environmental condition.