Abstract
Decrease of agricultural land and declining of the natural resources lead the farmers to seek
ways for sustainable intensification of the existing cropping systems. The conservation
agriculture (CA) based production systems may achieve these with less labor and energy and
higher economical profit margins. CA systems under different cropping patterns need to be
evaluated in terms of productivity, energy efficiency and economic profitability. There is an
urgent need to fine tune and re-adjust the existing two-wheel tractor operated strip tillage
planters in reference to blade design and shape, rotational speed and furrow openers for
different soil types and agro-ecological zones. Three experiments were conducted at Regional
Agricultural Research Station in Jamalpur and Barisal represented the loam and clay loam soils,
respectively. Four blades designed with varying tip angles were evaluated comparing with existing C shape blade by changing five level of rotational speed. Five types of furrow openers
were also designed and evaluated for strip tillage. Six cropping patterns and three tillage
systems were also evaluated in permanent plots. Six cropping patterns were i) Long
duration(LD) T. aman- Boro (winter rice) (CP1), ii) LD T. aman- Mungbean (CP2), iii) LD T.
aman - Wheat (CP3), iv) Short duration (SD) T. aman - Wheat - Mungbean (CP4), v) LD T.
aman - Maize (CP5) and vi) SD T. aman - Maize - Mungbean (CP6). Tillage treatments included
i) CA, ii) Mixed tillage (MT) and iii) Conventional tillage (CT). Torque and power requirement
in strip tillage was gradually decreased with decrease in blade tip angle and rotational speed.
The best combination of blade design and rotational speed was found under 15° at 320 rpm
which resulted in higher furrow cross sectional area (cm²), more soil backfill (%), and better
seeding depth than C type and 45° tip angle at different speeds. Further, these characteristics
facilitated better and uniform mean emergence time, higher emergence rate index (ERI) and
higher emergence percentage in both loam and clay loam soils. Though higher percentage of
desired soil aggregate group was produced in C blade at higher speed 560 rpm but, with
maximum soil loss due to more throwing pattern outside the furrow which resulted in poor soil
backfill. The newly designed inverted T furrow openers was narrower than shoe type openers
with longer hollow shank and provided better options for adjustment to achieve desired
seeding depth and line spacing. The better seeding depth, uniformity and higher soil backfill
was recorded in inverted T furrow opener with 65° rake angle which resulted for better soil
coverage on seed, higher ERI and maximum emergence percentage of maize, mungbean and
wheat than shoe type openers. The higher system rice equivalent yield (SREY) was observed
with interaction of CA system and CP4 pattern which was 41% higher than CT in CP1 but,
similar to MT and CP5, MT and CP4, CA and CP5. The maximum weeding time and cost was
recorded from CP6 pattern with CA. Fuel consumption for tillage systems was 78% lower in CA
than CT whereas CP5 required maximum fuel. The penetration resistance and soil bulk density
remained unchanged after 3 years of experiment. The soil temperature in CA at morning were
higher by 1-3 °C and it was vice-versa at evening than CT. The cropping system energy
requirement was found minimum with CA (33.67 GJha-1) with higher energy input-output ratio
than CT (40.12 GJha-1) and in other hand CP6 was found highest energy expensive. The
maximum benefit and cost ratio (BCR) was achieved with CA in CP5 and lowest was with CР1.
However, modified blade with 15° tip angle at 320 rpm rotational speed and the inverted T
furrow opener with 65° rake angle behind the blades was the optimum combination for strip tillage. Considering SREY, soil physical properties, energy efficiency and BCR, Rice-Maize
pattern with CA systems was the best option. Further research is needed to understand
mechanisms and performance of CA based systems in different intensifying environments of Bangladesh.