Influence of Different Moisture Conservation Practices and Crop Sequence on Direct Seeded Rice based Cropping System in Rainfed Ecosystem of Assam, India

Land configuration is one of the most critical factors for optimizing production potentials of crops and based on weather conditions, it acted as a management practices for crops (Deshmukh et al., 2016). During kharif season, Assam experiences heavy rainfall due to monsoon and there is records of complete failures of kharif crops particularly pulses due to water stagnation in the standing crop at vegetative stage. Therefore draining of water from the field is important for saving the crop from water stagnation. Broad Bed Furrow (BBF) method is an emerging practice of land configuration in rainfed farming system which acts as in-situ moisture conservation during dry periods as well as draining of water in furrows during heavy rainfall. Transplanting of rice is the traditional method of establishment of rice crop in Assam which requires high labour cost (Sharma et al., 2008). The direct seeding avoids some basic operations like nursery raising, uprooting of seedlings, puddling, transplanting, maintaining standing water and thereby reduces labour requirement (Pepsico International, 2011). Direct seeding can also be profitable and can increase the net return if production is more or less comparable with the transplanted rice. Greengram is a popular pulse crop among the farmers of Assam and it is grown mostly in kharif season (Mid August-first of September) although in some pockets it is also grown in February-March as summer greengram. In the rabi season toria, linseed, niger, buckwheat, potato, lentil, pea are some of the crops that are grown under rainfed situation of Assam and among them, linseed, niger, buckwheat are well suited in limited water supply. Therefore considering the importance of direct seeded rice as compared to sali rice to save time and cost in a cropping system approach to have 300% cropping intensity, in-situ conservation of moisture in kharif season and residual effect of land configuration coupled with residue incorporation, a trial was conducted at BN College of Agriculture, Assam Agricultural University, Biswanath Chariali, Assam during summer, kharif and rabi season of 2016-17 and 2017-2018 under rainfed condition.

The field experiments was conducted for two years (2016 -17 and 2017-18) in sequence starting with direct seeded rice (summer season) followed by greengram (kharif season) and four rabi crops (toria, linseed, niger and buckwheat) in rabi season The experiment was conducted at BN College of Agriculture, Biswanath Chariali of Assam Agricultural University, Assam The weather condition at Biswanath chariali is hot and humid during summer and cold and moist during winter. During 2016, in ahu rice growing season (March-July, 12^th SMW to 29^th SMW) total rainfall was 1112.5 mm distributed over 67 numbers of rainy days and in 2017, total rainfall was 1308.1 mm during the same period distributed over 63 rainy days. Average maximum temperature range was 24.9°C to 33.6°C during 2016 and 25.4°C to 33.2°C during 2017 and the minimum temperature range was 17.0°C to 26.7°C and 15.8°C to 26.3°C during 2016 and 2017, respectively. During growing period of greengram in the year 2016 and 2017 (33^rd SMW to 43^rd SMW), total rainfall received was 480.4 mm and 526.4 mm against the total evaporation of 226.6 mm and 207.8, respectively. During 2016, the mean maximum and minimum temperature ranged between 29.9°C to 34.3°C and 21.2°C to 26.9°C, respectively while in 2017, the mean maximum temperature ranged between 27.7°C to 34.1°C and minimum temperature ranged between 19.1°C to 25.9°C. The number of rainy days during greengram growing period was 25 and 27 in 2016 and 2017, respectively.  During the crop growing period of rabi crops in 2016-17 (45^th SMW to 11^th SMW) and 2017-18 (45^th SMW to 10^th SMW) total rainfall received were 83.4 mm and 120.7 mm against the total evaporation of 264.0 mm and 261.7 mm, respectively. The mean maximum and minimum temperature ranged between 20.4°C to 30.4°C and 9.2°C to 18.7°C during 2016 and during 2017, it ranged between 24.2°C to 28.8oC and 8.67°C to 18.9°C. The number of rainy days was 9 in 2016 and 10 days in 2017.
       
The soil of the experimental site was sandy loam in texture with an initial pH of 5.2 and 5.4 in 2016 and 2017, respectively. The organic carbon content was 0.59% and the initial available soil nitrogen, phosphorus and potash were in the range of low (259.10 kg ha^-1), medium (25.65 kg ha^-1) and low (112.30 kg ha^-1). The treatments consisted of 6 moisture conservation practices consisting land configuration of Flat bed and Broad Bed Furrow (BBF) along with crop residue incorporation. Two different sizes of BBF were studied consisting 60 cm and 120 cm width with a gap of 30 cm furrowsize in between beds. The treatments were Flat bed with crop residue incorporation (M₁), Flat bed with no residue incorporation (M₂), BBF 60-30 cm with residue incorporation (M₃), BBF 60-30 cm without residue incorporation (M₄), BBF 120-30 cm with crop residue incorporation (M₅) and BBF 60-30 cm without crop residue incorporation (M₆).
       
The experimental plot was ploughed by tractor drawn plough followed by one harrowing. Laddering was done properly to retain water uniformly in the field. After final land preparation the experimental field was divided into four blocks and each block was divided in to six main plots to allocate the six soil moisture conservation practices randomly, for growing summer (direct seeded ahu rice) and kharif (greengram) crops in sequence. The layout of the experiment consisting of the broad bed furrows at 60 cm and 120 cm apart, with 30 cm width furrow in between them were constructed manually along with the flatbeds, before sowing of rice crop. The main plots were again divided in to four sub-plots to allocate the rabi crops randomly following a split-plot design. Rice crop was sown accordingly with a spacing of 20 cm in both broad bed and flatbed surface of the soil. There were 3 rows of rice crop in one 60 cm bed and 6 rows of rice in 120 cm bed, while in flatbeds seeds were sown in usual lines of 20 cm apart.
       
For incorporation of crop residues the straw weight was recorded after harvesting the crop at the ground level followed by threshing. Then the rice straw (residue) was incorporated in the plots as per treatments by spreading them as uniformly as possible after the first opening of the plots to grow greengram in succession. The remaining plots were kept as such without crop residues. The follow up land preparation was carried out by hoeing manually without breaking the beds and furrows and greengram was also sown in all the sub-plots similar to that of direct seeded ahu rice.
       
In rabi season, after harvest of greengram by uprooting the plant, the remaining pods that left after field pickings were separated, weighed and incorporated in the plots as per treatments, similar to that of rice and greengram. The entire plots in each block were prepared manually, retained the broad bed furrows and four rabi crops viz. toria, linseed, niger and buckwheat were allocated randomly following split-plot design. Due to dis-similarity in biometric observations on different rabi crop parameters, RBD was followed for analyses of variance. The rabi crops were sown in lines at the recommended spacing of the crops. The fertilizer application and all other cultural practices were also performed as per recommendations of the crop.
       
The rice crop was sown in line with 20 cm spacing and in 60-30 cm bed, 3 rows of rice was allocated and in 120-30 cm bed, 6 rows of rice were allocated. The greengram crop was sown in 30 cm spacing in all the BBF and flat beds. The variety used for direct seeded rice was “Inglongkiri” which was developed by Regional Agricultural Research Station, Assam Agricultural University Diphu, having a average duration of 115-120 days. For greengram the variety SG-1 (Pratap) was selected for the study. In the first year rice crop was sown on 23.03.16 and in second year the rice was sown on 22.03.17 and harvested on 18.07.16 and 16.07.17, respectively. The second crop greengram crop was sown in 15.08.16 in the first year and 16.08.17 in second year and harvested on 24.10.16 and 22.10.17, respectively. The rabi crops were sown in the 2^nd week of November and harvested in Feb (toria, linseed and niger) and march (linseed).
       
For all the crops, yield attributes and yield were recorded and analyzed statistically for interpretation of the data. The individual crops were analyzed in RBD and system parameters were analyzed in split plot design.

Yield attributes of rice
 
The panicle sm^-2 under BBF 60-30 cm with residue (113.00 and 117.69 in 2016 and 2017 and without residue (112.69 and 113.75 in 2016 and 2017 which was equal to BBF 120-30 cm with residue (109.56 and 113.63 in 2016 and 2017, respectively. The BBF 60-30 cm with residue incorporation resulted in significantly higher values of grains panicle^-1 over both flatbeds with or without residue incorporation (Table 1).


       
The higher number of effective panicles m^-2 and grains panicle^-1 under BBF may be due to better growth of the crop resulting from more retention and conservation of water in the furrows which was utilised during rainless periods. Higher number of grains panicle^-1 (Kaur and Dhaliwal, 2015) and grains panicle^-1 (Hobbs and Gupta, 2003) of rice due to better growth of the crop under raised bed sowing method than the flatbed method was also reported.
 
Grain and straw yield
 
In 2016, the grain yield under the treatments BBF 60-30 cm with (23.43 q ha^-1) and without residue (22.72 q ha^-1) and BBF 120-30 cm with residue (22.81 q ha^-1) were at par and BBF 60-30 cm with residue produced significantly higher grain yield over rest of the treatments. In 2017, BBF 60-30cm with residue (25.70 q ha^-1) significantly out yielded all other treatments (Table 1). The pooled data over the years revealed that BBF 60-30 cm with residue (24.56 q ha^-1) produced significantly higher grain yield over rest of the treatments. In rice-wheat cropping system, the increase of rice yield by 33% and wheat yield by 60% in the permanent bed sowing method was reported by Singh et al., (2011).
 
Yield attributes of kharif greengram
 
The treatment BBF 60-30 cm both with and without residue incorporation produced significantly higher number of clusters plant^-1 over rest of the treatments during both 2016 and 2017 (Table 2). In respect to number of pods cluster^-1, in 2016, BBF 60-30 cm and BBF 120-30 cm with and without residue incorporation showed at par effect but significantly higher over both flatbed methods. While in 2017, the effect of BBF 60-30 cm with and without residue incorporation and BBF 120-30 cm without residue incorporation on number of pod cluster^-1 were significantly higher over rest of the treatments. In case of number of seeds pod^-1 and 1000 seed weight, higher values were recorded under BBF 60-30 cm with residue incorporation. The optimum moisture availability due to the adequate drainage of excess rain water through the furrows in BBF methods might have resulted in better yield attributing characters compared to flatbed sowing. A similar result of increased yield attributes of kharif greengram viz., number of clusters plant^-1 and pod cluster^-1 due to the land configuration of BBF compared to flatbed method was also reported by Tomar (2013).


 
Seed and stover yield
 
Both the treatment BBF 60-30 cm and BBF 120-30 cm with and without residue incorporation resulted in statistically at par seed and stover yield and produced significantly higher values over the flatbed (Table 2). The highest seed (9.58 q ha^-1 and 10.63 q ha^-1 in 2016 and 2017, respectively) and stover yield (27.62 q ha^-1 and 29.26 q ha^-1, in 2016 and 2017, respectively) were recorded with the treatment BBF 60-30 cm with residue followed by BBF 60-30 cm without residue and BBF with and without residue incorporation. The BBF 60-30 cm with residue incorporation resulted in higher seed and stover yields by about 35.6% and 39.3% over the flatbed methods with or without residue incorporation. The higher yield attributes like number of clusters plant^-1, pods cluster^-1 and seeds pods^-1 (Table 2) under the treatment BBF 60-30 cm might have attributed to higher seed and stover yield of greengram. Increased seed and stover yield of chickpea and safflower by 12.5% and 10.7% in BBF planting over traditional flatbed method were also reported by Khambalkar, (2014).
 
Rabi crops
 
Yield attributes and yields of buckwheat
 
The number of cymes plant^-1 and 1000-seed weight (Table 3) of buckwheat did not vary significantly due to different moisture conservation practices in both the year. But the number of seeds cyme^-1 was significantly higher under the treatment BBF 60-30 cm with or without crop residue incorporation over the flat bed methods and the lowest seeds cyme^-1 was recorded in flat bed without residue.


       
In regards to seed and stover yields (Table 3) in both the year, BBF 60-30 cm with and without residue incorporation brought about significantly higher values over that of flatbeds with and without residue incorporation. Pooled data over the years also showed similar results in both the cases. Similar results of the increased seed yield of safflower due to different land configurations over the flat bed sowing was also reported by Khambalkar (2014).
 
Yields attributes and yield of linseed
 
During both the year, different moisture conservation practices significantly influenced the number of capsules plant^-1 while the number of seeds capsule^-1 and 1000-seed weight did not vary significantly. In both year, the seed yield (Table 4) of linseed due to BBF 60-30 both with (6.13 and 6.29 q ha^-1 during 2016-17 and 2017-18) and without residue (5.50 and 5.72 q ha^-1 during 2016-17 and 2017-18) and BBF 120-30 cm with residue incorporation (5.80 and 5.96 q ha^-1 during 2016-17 and 2017-18) were at par and BBF 60-30 with residue produced significantly higher seed yield over rest of the treatments. From the results of a field experiment carried out at Madhya Pradesh, Gupta (2018) also observed higher yield attributes and seed and stover yields of soybean under Broad Bed Furrows compared to flat beds.


 
Yield attributes and yields of niger
 
In both the year, BBF 60-30 cm and BBF 120-30 cm with residue and without residue resulted in at par effect and recorded higher capitula plant^-1 over flatbed methods of sowing (Table 5). Similar trend of results was also observed in regards to number of seeds capitula ^-1 during both the year. The seed and stover yield of niger showed higher in both BBF 60-30 cm and BBF 120-30 cm as compared to flatbed method of moisture conservation (Table 5).


 
Yield attributes and yield of Toria
 
During both the year, different moisture conservation practices brought about significant impact on number of siliqua plant^-1 of toria (Table 6). But it failed to show any significant variation on number of seeds siliqua^-1 and 1000-seed weight of toria. In 2016-17, the seed yield due to BBF 60-30 cm and BBF 120-30 cmand in 2017-18, BBF 60-30 cm both with and without and BBF 120-30 cm with residue incorporation were at par and significantly higher values of seed yield were recorded under BBF 60-30 cm with residue (6.10 and 6.34 q ha^-1 during 2016-17 and 2017-18, respectively) over other treatments (Table 6). Due to better tillering and crop growth, 12% higher wheat grain yield with ridge furrow planting in comparison to farmer’s practice of flat planting was reported by Hussain (2018).


 
Rice equivalent yield (REY) of rice-based cropping systems
 
The rice equivalent yields of the system (Table 7) were significantly influenced by different moisture conservation practices. In 2016-17, BBF 60-30 cm and BBF120-30 cm both with residue (81.77 q ha^-1 and 77.80 q ha^-1) and without residue (79.03 q ha^-1 and 76.47 q ha^-1) produced statistically similar REY and all being significantly higher over flatbed method of sowing both with (64.29 q ha^-1) and without residue incorporation (63.56 q ha^-1). In 2017-18, the highest REY was recorded with the treatment BBF 60-30 cm with residue (89.64 q ha^-1) which was at par with BBF 60-30 cm without residue (82.56 q ha^-1) and BBF 120-30 cm with residue incorporation (82.47 q ha^-1), but significantly higher over rest of the treatments. The lowest value was recorded under flatbed without residue incorporation (66.05 q ha^-1).


       
During both the year, the REY (Table 7) due to different crop sequences varied significantly. In 2016-17, the REY of direct seeded rice-greengram-toria (78.13 q ha^-1) and direct seeded ahu rice-greengram-linseed (74.75 q ha^-1) were at par and the effect of direct seeded rice-greengram-toria was significantly higher over direct seeded ahu rice-greengram-niger (72.58 q ha^-1) and direct seeded ahu rice-greengram-buckwheat (69.80 q ha^-1). In 2017-18, the crop sequences viz. direct seeded ahu rice-greengram-toria (81.97 q ha^-1), followed by direct seeded ahu rice-greengram-linseed (79.28 q ha^-1) and direct seeded ahu rice-greengram-niger (77.29 q ha^-1) resulted in similar values and direct seeded rice-greengram-toria showed significantly higher rice equivalent yield over direct seeded ahu rice-greengram-buckwheat (74.90 q ha^-1).
       
It was observed that, direct seeded ahu rice, being the base and uniform crop, the REY of different crops of the cropping systems mostly influenced by both kharif greengram and rabi crops. Besides, the higher production potential of toria as compared to the other rabi crops and the better market price of toria contributed much for attaining higher REY under the sequence. This is in conformity with the findings of Kalita (2015) and Baishya (2016).
 
Economics
 
In both year, the highest cost of cultivation was associated with the treatment BBF 60-30cm (Rs. 56,815/ha and 58,315/ha, in 2016-17 and 2017-18) (Table 8). This was mainly due to the cost involved in preparation of broad bed furrows as per closure and widened sizes of the beds and associated cost of residues and labour engaged in incorporation.  During both the year, considerably higher gross (Rs.94,035 ha^-1 and 1,03,086 ha^-1, in 2016-17 and 2017-18, respectively) and net return (Rs.37,220 ha^-1 and 44771 ha^-1, in 2016-17 and 2017-18, respectively) were recorded with the treatment BBF 60-30 cm with residue incorporation compared to other treatments. The lowest gross return of Rs. 74,525 ha^-1 was obtained under flatbed without residue incorporation.


 

The moisture conservation practices of Broad Bed Furrow system of land configuration along with residue incorporation was beneficial in regards to yield attributes and yield of summer, kharif and rabi crops grown as rice-based cropping systems under the soils and climatic conditions in rainfed situation of Assam. Among the BBF, the bed size of 60-30cm was better as compared to the 120-30 cm size bed. The BBF coupled with residue incorporation had not only influenced the crop performance but also helped in getting higher economic return. Among the crop sequences, Direct seeded ahu rice-greengram-toria was the most performing crop sequence in terms of higher rice equivalent yield, less cropping duration with better production efficiency, employment generation and economic return. However the linseed and niger can also be advocated as an alternative to toria as their performance was also better under rainfed situation in rabi season of Assam.

None.