The study locations were (site-1, site-2 and site-3) under the agro ecological zone AEZ-13 (Ganges Tidal Floodplain). The experimental site-1 was at Patuakhali sadar under Patuakhali. The site-2 was at Borguna sadar under Borguna. The site-3 was at Barisal sadar under Barisal. One farmer from each site was selected to conduct the field experiment. Each crop of the experiment comprised one treatment. Three treatments were imposed: T1= No biomass incorporation + Recommended fertilizer (RF) for T. aman, T2= Mungbean biomass incorporation + 50% of RF for T. aman, T3= Cowpea biomass incorporation+ 50% of RF for T. aman. The experiment was laid out in a randomized complete block design (RCBD) with five replications. Each replication represented a block which was divided into three unit plots. The size of the individual unit plot was 2.5 decimal. Plot to plot distance was maintained 0.5 m. A boarder area of 1m around the experimental field was also maintained.
The first crop in the cropping pattern was mungbean (var. BARI mung-6, about 1.2-1.5 t ha-1 yield potential) and cowpea (var. BARI felon-1, about 1.3-1.7 t ha-1 yield potential). After land preparation mungbean seeds of BARI mung-6 were sown in line maintaining line to line distance 30 cm and plant to plant distance 5 cm. And cowpea seeds of BARI felon-1 were sown in line maintaining line to line distance 30-40 cm and plant to plant distance 10 cm. The unit plot size was 10 m x 10 m for both crops. Seed sowing dates are presented in the following table:
|
Location
|
Mungbean
|
Cowpea
|
|
2012-13
|
2013-14
|
2012-13
|
2013-14
|
|
Patuakhali sadar
|
25 January 2013
|
02 February 2014
|
21 December 2012
|
30 December 2013
|
|
Borguna sadar
|
30 January 2013
|
07 February 2014
|
31 December 2012
|
26 December 2013
|
|
Barisal sadar
|
25 January 2013
|
03 February 2014
|
25 December 2012
|
15 December 2013
|
The second crop was T.aman rice (Yield potentially: 3.00-5.00 t ha-1). After pod harvesting of mungbean/cowpea, biomass of BARI Mung-6 and BARI Felon-1 were incorporated to soil. Afterwards, experimental plots were ploughed 3-4 times to cultivate T.aman crop. Plots were surrounded by raised bunds to limit fertilizers within the plots. Seedlings of Local/HYV were raised in well prepared seedbeds. The unit plot size was 10 m x 10 m with spacing of 25 cm x 20 cm for both varieties (Local/HYV). Thirty five-forty five days old seedlings were transplanted in the main field. Sowing and transplanting dates are presented in the following table:
|
Location
|
Variety name
|
Year
|
Seed sowing date
|
Transplanting date
|
|
Patuakhali sadar
|
Local (Mota dhan)
|
2012-13
|
21 July 2013
|
29 August 2013
|
|
Local (Moulota dhan)
|
2013-14
|
09 July 2014
|
17 August 2014
|
|
Borguna sadar
|
Local (White Mota dhan)
|
2012-13
|
16 July 2013
|
29 August 2013
|
|
Local (White Mota dhan)
|
2013-14
|
10 July 2014
|
23 August 2014
|
|
Barisal sadar
|
BRRI dhan 41
|
2012-13
|
19 July 2013
|
22 August 2013
|
|
BRRI dhan 41
|
2013-14
|
11 July 2014
|
14 August 2014
|
In case of mungbean/cowpea full amount of urea, TSP and MoP as per treatments were applied at the time of final land preparation. In case of mungbean, fertilizers were applied in plot at the rate of 40-80-30 kg/ha as urea, TSP and MoP, respectively. In case of cowpea, fertilizers were applied in plot at the rate of 20-40-20 kg/ha urea, TSP and MoP, respectively. In case of T.aman rice, the amount of TSP and MoP and one-third of urea were applied during final land preparation according to treatment dose. Rest of the urea was top dressed in two equal installments at tillering stage and panicle initiation stage. Urea, TSP, MoP, Gypsum was applied @ 130, 50, 80, 50 kg ha-1 (FRG-2012) in plot, respectively. But in case of T1, 100% of recommended fertilizers were applied and in case of T2 and T3, 50% of recommended fertilizers were applied.
After germination of seedlings, thinning was done to maintain optimum plant population in the experimental plots. Weeding was done at 20 days after sowing (DAS) and at 45 DAS to keep the experimental plots weed free for the whole period of the crop growth. Insecticide Admire was applied twice- before flowering and during flowering with an interval of 10 days to protect from thrips. No hill was missed, so there was no need to gap filling. Weeding was done at 15 days after transplanting (DAT) and at 45 DAT to keep the experimental plots weed free for the whole period of the crop growth. In case of HYV, no insect or disease was infected, so there was no need to use any pesticide. In case of Local variety, stem borer infestation was observed and was controlled by spraying Vittaco. Top dressing of urea was done according to recommendation mentioned above.
Mungbean (BARI mung-6) and Cowpea (BARI felon-1) was harvested twice. First only ripen pods were harvested. After first picking, flowering appeared and pod formation occurred second time. These pods were harvested second time after ripening. Only ripen pods were harvested. After picking the pods, the remaining biomass of mungbean/cowpea was incorporated in the soil. Harvesting dates are presented in the following table:
|
Location
|
No. of harvest
|
Mungbean
|
Cowpea
|
|
2012-13
|
2013-14
|
2012-13
|
2013-14
|
|
Patuakhali sadar
|
1st harvest
|
02 April 2013
|
08 April 2014
|
12 April 2013
|
18 April 2014
|
|
2nd harvest
|
14 April 2013
|
19 April 2014
|
24 April 2013
|
30 April 2014
|
|
Borguna sadar
|
1st harvest
|
08 April 2013
|
12 April 2014
|
19 April 2013
|
14 April 2014
|
|
2nd harvest
|
22 April 2013
|
22 April 2014
|
30 April 2013
|
28 April 2014
|
|
Barisal sadar
|
1st harvest
|
01 April 2013
|
10 April 2014
|
11 April 2013
|
10 April 2014
|
|
2nd harvest
|
12 April 2013
|
22 April 2014
|
26 April 2013
|
25 April 2014
|
T. aman (Local/HYV) was harvested when 80% grain were ripen. In experiment, data on yield and yield contributing characters were collected from 10 (ten) randomly selected hills from each per plot and then converted into yield per hactare. Threshing, cleaning and drying of grain were done separately plot-wise. The weights of grain were recorded plot-wise. Harvesting dates are presented in the following table:
|
Location
|
Harvesting date
|
|
2012-13
|
2013-14
|
|
Patuakhali sadar
|
21 December 2013
|
09 December 2014
|
|
Borguna sadar
|
17 December 2013
|
08 December 2014
|
|
Barisal sadar
|
15 December 2014
|
08 December 2014
|
At harvest, yield and yield components data were recorded and analyzed statistically. Computation and preparation of graphs were done using Microsoft Excel 2003 Program.