Conservation agriculture based tillage and crop establishment options can maintain farmers’ yields and increase profits in South Asia's rice–maize systems: Evidence from Bangladesh

Field Crops Research 172 (2015) 85–98

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Conservation agriculture based tillage and crop establishment options can maintain farmers’ yields and increase profits in South Asia’s rice–maize systems: Evidence from Bangladesh Mahesh K. Gathala a,∗ , Jagadish Timsina a,b , Md. Saiful Islam a , Md. Mahbubur Rahman c , Md. Israil Hossain c , Md. Harun-Ar-Rashid d , Anup K. Ghosh e , Timothy J. Krupnik a , Thakur P. Tiwari a , Andrew McDonald f a

International Maize and Wheat Improvement Center, House 10/B, Road 53, Gulshan-2, Dhaka 1212, Bangladesh Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Parkville 3010, VIC, Australia c Regional Wheat Research Center, Bangladesh Agricultural Research Institute, Rajshahi, Bangladesh d Regional Rice Research Station, Bangladesh Rice Research Institute, Rajshahi, Bangladesh e RDRS, Rangpur, Bangladesh f International Maize and Wheat Improvement Center, PO Box 5186, Singha Durbar Plaza Marg Bhadrakali, Kathmandu, Nepal b

a r t i c l e

i n f o

Article history: Received 23 October 2014 Received in revised form 30 November 2014 Accepted 2 December 2014 Available online 20 December 2014 Keywords: Conservation agriculture Rice–maize system Tillage Crop establishment Profitability On-farm trial

a b s t r a c t Rice–maize (R–M) systems are rapidly expanding in South Asia and Bangladesh due to higher yield and profit potential from rabi (winter) maize, its reduced water requirement compared to rice–rice systems, and increasing demand from poultry and fish feed industries. The current practice of growing puddled transplanted rice and maize with conventional, repeated tillage degrades soil structure, delays maize planting, and reduces its yield potential, increasing energy and labour requirements, ultimately leading to high production costs. Conservation agriculture (CA)-based tillage and crop establishment options such as strip or reduced tillage, and raised beds, may hold potential to increase yield, reduce crop establishment costs, and increase income of the farmers. The objective of this study was to evaluate the productivity and profitability of R–M systems under CA-based tillage and crop establishment options across a gradient of 69 farmers’ fields in Northwest Bangladesh. We evaluated four tillage and crop establishment options: reduced tillage; strip tillage; fresh beds; and permanent beds. Conventional-tilled (puddled) transplanted rice on flat followed by conventional-tilled maize on flat was included as a current practice. ANOVA for adjusted 4-year pooled mean revealed no significant treatment effects for yield and economic analysis parameters for rice (P ≥ 0.05), but they were significant for maize and the R–M system (P ≤ 0.05). Rice yields across tillage and establishment treatments over four years ranged from 4.6 to 4.9 t ha−1 while maize and R–M system yields ranged, respectively, from 7.8 and 12.5 t ha−1 under conventional tillage to 9.0 and 13.8 t ha−1 on permanent beds. Compared to conventional tillage, the average maize and system yield across fresh beds, reduced tillage, and strip tillage, was greater by 9.1% and 6.1%, respectively. Maize production costs ranged from US $922 ha−1 with fresh beds to US $1,027 ha−1 for conventional tillage. Maize net returns and benefit cost ratio (BCR), however, ranged, respectively, from $945 ha−1 and 1.9 under conventional tillage to $1350 ha−1 and 2.4 under permanent beds. We conclude that while CA-based tillage and establishment options may not have significant yield advantage over conventional tillage in rice, they have significant advantages in terms of reduced production cost and labour use, and increased net returns. For maize as well as for R–M system, while most options can provide yield benefits similar to conventional tillage, permanent beds exhibit a significant advantage (yield, net returns, etc.) over conventional tillage. Profitability was consistently greatest and significantly different (P ≤ 0.001) under permanent raised beds compared to all other treatments. Considering our assessment of the profitability distributions and risk analysis, we conclude that both rice and maize planted sequentially on permanent beds and strip tillage can result in higher net income and BCR compared to conventional tillage practice. © 2014 Elsevier B.V. All rights reserved.

∗ Corresponding author. Tel.: +880 1755577390. E-mail address: [email protected] (M.K. Gathala). http://dx.doi.org/10.1016/j.fcr.2014.12.003 0378-4290/© 2014 Elsevier B.V. All rights reserved.

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1. Introduction Cropping systems in Bangladesh typically include monsoon (aman) rice (Oryza sativa L.) during the rainy kharif season, followed by a second rice (boro) crop (R–R system) in areas where irrigation water is in ample supply. Where water is scarce or insufficient, maize (Zea mays), wheat (Triticum aestivum), potatoes (Solanum tuberosum), or other crops are grown instead of boro for higher yields and profits, or for diverse dietary needs and nutrition. Of all systems, R–R and rice–wheat (R–W) have historically underpinned food security in South Asia (Timsina and Connor, 2001). Market demand for maize in South Asia and Bangladesh has significantly increased in the last decade, a result of the expanding poultry and fish feed industries, and also as a processed food (Ali et al., 2008; Timsina et al., 2010). As a result, maize area and production has increased substantially in the region. The increase is especially remarkable in Bangladesh, where cultivated land area with maize jumped from 0.05 M ha in 2000 to >0.31 M ha in 2012–2013 (DAE, 2014). Almost all maize grown in Bangladesh is hybrid, with average yield being highest among the South Asian countries (http://faostat3.fao.org/compare). Excluding Pakistan, for which exact area data for rice–maize (R–M) systems are not available, these systems occupy approximately 1.31 M ha in Bangladesh, India, and Nepal, indicating their importance in the region. In low-lying fields in Bangladesh, and particularly in areas adjacent to river systems with heavier textured soils, farmers commonly confront production challenges posed by excess soil moisture following the monsoon aman rice harvest, resulting in main two difficulties in establishing a subsequent maize crop. First, tillage operations of any kind are not advisable until the soil dries sufficiently to allow traffic without compaction or slippage. Second, excess moisture can increase disease incidence, seed rot, and impede germination and seedling establishment, especially when soil temperature is cool. As a result, where moisture is excessive and farmers use conventional tillage, which in Bangladesh usually involves up to 3–5 passes of a slow-speed rotary tillage with a two-wheel tractor (2WT) driven power tiller, farmers may have to wait 2–3 weeks after rice harvest to carry out these tillage operations can require another 1–2 weeks before planting maize, thus delaying planting considerably. Conventional tillage requires considerable time, fuel, labour, and water, resulting in high production costs, reduced profits, and in some cases increased greenhouse gas emissions relative to alternative options (Johansen et al., 2012). Furthermore, late-planted maize can be affected by heat stress, and under rainfed conditions by drought, as these stresses which buffer the flowering period can severely affect seed set and maize yield (Bänziger et al., 2000). Late-planted maize can also be affected by pre-monsoon storms that cause lodging which affects both grain quality and yield. Simulation studies have shown that to achieve high yield potential and to narrow yield gaps, maize must be planted as early as possible after rice harvest (Timsina et al., 2010, 2011). Conservation agriculture (CA)-based technologies such as zero, strip, reduced tillage, or permanent raised beds may under some circumstances facilitate improved crop establishment and timely sowing, increase yield, reduce irrigation water requirements, lower production costs, and boost income, though they have yet to be systematically studied as they perform under on-farm conditions in Bangladesh. Advocates commonly cite that CA-based systems perform better in the long-run in terms of yield increase (Gathala et al., 2011a,b; Hobbs, 2007; Jat et al., 2009, 2014) and improvements in soil health, system resilience, and sustainability (Connor et al., 2003; Hobbs et al., 2002; Sayre and Hobbs, 2004), although yield potential relative to conventional tillage has been widely debated (cf. Pittelkow et al., 2014). Nonetheless, several large scale adoption surveys in neighboring India report lower production costs,

higher net returns and benefit cost ratio (BCR), and lower water, labour and energy requirements for zero-tilled compared to the conventionally-tilled wheat, indicating that farmers are motivated by more than yield (Erenstein and Laxmi, 2008; Jat et al., 2014; Saharawat et al., 2010). In other studies, shifting from conventional tillage to zero tillage in wheat decreased input costs by 20–59% and increased net revenue by 28–33% (Aryal et al., 2014; Kumar et al., 2013a,b). In contrast, a few studies also showed little difference or even lower wheat yield under zero tillage than conventional tillage (Tahir et al., 2008; Tripathi et al., 2007). In rice, Bhushan et al., 2007 reported that yields in conventionally-tilled puddle transplanted rice (TPR) and conventionally-tilled direct seeded rice (DSR) under non-puddled or puddled conditions were equal, while Saharawat et al. (2010) and Gathala et al. (2013) reported that both zero-tilled DSR and non-puddled TPR produced higher yield and profits than the conventionally-tilled puddled TPR. Hobbs et al. (2002) and Connor et al. (2003) proposed permanent raised beds as a means of increasing the productivity and profitability of R–W systems. As a variant of zero-tillage, they hypothesized that permanent beds offer potential additional advantages for both crops through saving irrigation water and improving soil structure through controlled traffic. But they also cautioned that bed systems may not be suited for rice on light soils because of exacerbated water losses by percolation. Yadvinder-Singh et al. (2009) reported that on the light-textured soils of the Northwest IndoGangetic Plain (IGP), wheat yields in R–W systems on fresh and permanent beds were similar to those under conventional tillage on loams, though they tended to be lower on permanent beds on sandy loams. Likewise, Choudhury et al. (2006) reported that wheat yields were reduced by 12–17% on raised beds compared to flats on a loamy soil in the Northwest IGP. In rice following wheat, Choudhury et al. (2006) and Bhushan et al., 2007 reported 14–42% reduction in DSR yield under raised beds compared to flat. Likewise, Yadvinder-Singh et al. (2009) reported that DSR yields on permanent beds declined to 33–44% and that on fresh beds were 7–15% of the conventionally-tilled puddled TPR yields. Lastly, Kukal et al. (2010) also reported a significant decline in DSR yield on permanent beds relative to puddled TPR on both loamy and sandy loam soil, also in Northwest IGP. Hence, there is considerably uncertainty about the benefits of bed planting and in which production environments the technology most sensibly fits. In contrast to the findings from Northwest India, researchers from Bangladesh and Nepal reported yield benefits from growing crops under R–W and R–M using permanent beds (Hossain et al., 2004b; Lauren et al., 2008; Talukder et al., 2008). In a review of the subject, Humphreys et al. (2008) concluded that rice on permanent beds performed generally better in the Northeast compared to Northwest IGP, despite similar soils. Thus although soil types and rainfall regimes may largely influence the adaptability of bed planting systems, it needs to be emphasized that the abovementioned studies on permanent beds in the Northwest IGP were conducted with large 4-wheeled tractors (4WTs), whereas over 450,000 two wheeled tractors (2WTs) predominate in Bangladesh (Krupnik et al., 2013). Due to the different traction characteristics and the different types of implements these tractors bear, it might be expected that the resultant tillage effects would differ from 4WTs and 2WTs (Kukal et al., 2008). Thus the reported findings in the Northwest Indian IGP might be expected to differ from what may be found with 2WTs in Bangladesh. Above studies suggest that though substantial research and development efforts are underway to introduce, evaluate, and disseminate CA-based crop establishment practices, especially for R–W systems in South Asia, the vast majority of farmers still establish crops with conventional tillage under different cropping systems. In contrast, only a few studies have evaluated CA-based tillage and crop establishment options for R–M systems in South

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Asia. Examples include Talukder et al. (2008) who reported highest grain yield of each crop in rice–wheat–maize systems (with maize in kharif-1) on permanent beds with 50–100% straw retention, but least under conventional flat tillage without straw retention in Northwest Bangladesh. Similarly, Singh et al. (2010) reported significant savings in inputs and improved system productivity under permanent raised beds both with and without residues in Eastern India. Kadiyala et al. (2012) reported significantly higher yields in no-till maize grown after aerobic rice than flooded rice in Hyderabad in South India, which they attributed to residual soil N and improved soil physical conditions. Compared strip tillage with conventional tillage under two years of R–M rotation at two contrasting on-station locations in Bangladesh, Krupnik et al. (2014a) found that at one location, there were no differences between the tillage systems in either year, while in the other location, conventional tillage performed better in the first year but strip tillage in the second year. Clearly, given the lack of consensus on these issues, identification of appropriate tillage and crop establishment options in R–M systems in necessady for rice production and food security, and profitability of farmers’ enterprises given the burgeoning feed demand from poultry and fish industries in Bangladesh and South Asia. Hence, in response to this knowledge gap and to test the hypothesis that the CA-based interventions have similar benefits in the R–M systems of South Asia, we evaluated four alternative tillage and crop establishment options for rice and maize grown in sequence for four years in 69 farmers’ fields, in which farmers implemented each treatment themselves with researcher backing, in four sub-districts (upazilas) across two districts in Northwest Bangladesh. 2. Materials and methods 2.1. Site and soil characteristics Studies were implemented in R–M systems dispersed over two upazillas each in Rajshahi (25◦ 0 0 N; 88◦ 0 0 E) and Rangpur 25◦ 50 0 N; 89◦ 0 0 E) districts in Northwest Bangladesh (Fig. 1), and spread over four years from aman rice (2009) to rabi maize (2012–2013), thus four seasons each of rabi maize and aman rice. Rajshahi is situated in the Active Ganges Floodplain in agroecological zone (AEZ) 10) while Rangpur is spread over both Active Tista and Tista Meander Floodplains (AEZ 2 and 3) (FAO, 1988). The major land types in Rajshahi are highlands (HL; 12%), medium highlands (MHL; 33%), and medium lowlands (MLL; 18%) while in Rangpur are HL (35%) and MHL (51%). In general, in Rajshahi, soil organic matter (SOM) is low, and N, P, K, and S contents of soils are low, low to medium, medium, and low to medium, respectively, while in Rangpur, SOM is low, and N, P, K, and S contents in soils are low to very low, low to medium, low, and low, respectively (BARC, 2012). Rangpur farmers’ soils were loam to silt loam (as per USDA classification) with 37.7% sand, 51.6% silt, and 10.7% clay but Rajshahi soils were sandy clay loam to loam with 45.9% sand, 27.5% silt, and 26.6% clay (Table 1) Participating farmers’ fields in Rangpur were acidic, but in Rajshahi they were slightly alkaline. Soil organic carbon (SOC) was higher in Rajshahi than Rangpur. Soil total N in both districts was low but soil available P was higher than the critical level of 14 mg kg−1 (for aerobic crops). Soil exchangeable K in both districts was also higher than the critical level of 0.1 cmol kg−1 (for lowland rice), and less than 0.2 cmol kg−1 (for upland crops). 2.2. Climatic characteristics 2.2.1. Maize season Weather patterns in both districts varied across the four rabi maize growing seasons. In Rajshahi, there was no rainfall during

Fig. 1. Map of Bangladesh showing the location of on-farm trial sites in Rajshahi and Rangpur districts (Dots represent locations of 69 farmers’ fields, dots are overlapping due to large scale).

the maize season in 2009–2010, while slight rainfall (∼30-mm) occurred at sowing in December in 2010–2011, little rainfall in January and March in 2011–2012 and high rainfall (∼100-mm) at sowing in November in 2012–2013 (Fig. 2). In Rangpur also, except during the reproductive stage of maize in April, there was no rainfall during maize season in 2009–2010, intermittent and little rainfall (10–20-mm) during Feb–April in 2010–2011, and high rainfall in both April 2011–2012 (∼200-mm) and April in 2012–2013 (140-mm) (Fig. 3). Both maximum and minimum temperatures in Rajshahi were lowest (10–13 ◦ C) during vegetative stage in January and highest (35–38 ◦ C) during reproductive stage in April–May Table 1 Soil properties (0–15 cm depth) of the participatory farmers’ fields of Rajshahi and Rangpur districts, Bangladesh. Soil property

Rajshahi (n = 35) Mean

pH SOC (%) Total N (%) Avail. P (mg kg−1 ) Exch. K (cmol kg−1 ) Soil texture/class† Sand (%) Silt (%) Clay (%) ! †

SD!

7.58 ±0.59 0.88 ±0.32 0.06 ±0.02 32.76 ±20.01 0.19 ±0.09 Sandy clay loam to loam 45.92 ±6.00 27.54 ±9.40 26.55 ±4.98

SD = standard deviation. Soil class as per USDA standards.

Rangpur (n = 34) Mean

SD

5.62 ±0.79 0.75 ±0.31 0.06 ±0.03 46.81 ±32.89 0.32 ±0.16 Loam to silt loam 37.65 6.16± 51.64 8.07± 10.70 6.70±

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Rajshahi

Rainfall (mm)

Max.Temp ⁰C

Min.Temp ⁰C

Sunshine (hrs)

500 450

35

400 30 350 25

300

20

250 200

15

Rainfall (mm)

Sunshine (hrs) and temperature (0C)

40

150 10 100 5

50

0

0

2009

2010

2011

2012

2013

◦

Fig. 2. Mean monthly sunshine (h) and minimum and maximum temperatures ( C) and total rainfall (mm) from 2009 to 2013 in Rajshahi district of Bangladesh.

in all years. In Rangpur, minimum temperatures were similar to, but maximum temperatures were slightly lower, than those in Rajshahi. 2.2.2. Rice season Weather patterns during the rice growing season also varied across years. Total monthly rainfall in Rajshahi in June alone ranged from as low as 125 mm in 2009 and 2012 to as high as 350 mm in 2011, and in July, total rainfall ranged from about 140-mm in 2010 to about 320-mm in 2012 (Fig. 2). There was highest monthly rainfall (about 450-mm) in August in 2011. Years 2010 and 2012 were relatively dry, though 2011 had a wetter rice season compared to 2009. In Rangpur, total monthly rainfall during the rice season was much higher than in Rajshahi. Total rainfall ranged from about 300 mm in 2009 and 2011 to about 650-mm in 2010 in June alone, and from about 275-mm in 2009 to 450-mm in 2011 in July alone. In August of 2009 and 2011, there was very high rainfall (850 and 550-mm, respectively) while for the same month in the other two years, there was a relatively low rainfall (∼200-mm) (Fig. 3). In

Rangpur

Rainfall (mm)

2.3. Trial design and treatments description Farmers in each district typically follow conventional tillage (CT) for both rice and maize. Participating farmers were selected based on their willingness, interest, and their commitment to participate in multi-year on-farm trials by agreeing to follow the trial protocols and to provide in-kind contribution (i.e., family labour, land, irrigation water, etc.). Although we provided key inputs (i.e., seeds,

Max.Temp ⁰C

Min.Temp ⁰C

900

Sunshine (hrs)

800

35

700

30

600 25 500 20 400 15 300 10

200

5

100

0

0

2009

2010

2011

20 1 2

2 013

Fig. 3. Mean monthly sunshine (h) and minimum and maximum temperatures (◦ C) and total rainfall (mm) from 2009 to 2013 in Rangpur district of Bangladesh.

Rainfall (mm)

Sunshine (hrs) and temperature (0C)

40

both districts, there was very little rainfall at the end of the rice season during late September and the whole of October, resulting in terminal water stress in rice in some fields. June rainfall is important for sowing DSR, while July rainfall is more important for puddled or non-puddled transplanted rice. Both maximum and minimum temperatures were much higher in the rice season compared to the maize season. Maximum temperatures during the rice season from June to September remained between 30 and 35 ◦ C while the minimum temperatures were between 20 and 25 ◦ C, and both were slightly higher in Rajshahi than in Rangpur.

M.K. Gathala et al. / Field Crops Research 172 (2015) 85–98

fertilizers, CA-based planting machines for sowing crops (see later), and herbicides), farmers contributed their own labour for sowing, irrigating, fertilizing and managing fields, and for harvesting and threshing/shelling. In addition, we purposefully selected farmers whose fields were on different soil and land types so as to have the ability to broadly assess the CA-based tillage and crop establishment options. Using an unbalanced incomplete block design, we evaluated three CA-based tillage and crop establishment options: strip tillage (ST), reduced tillage (RT), and permanent beds (PB) In addition, a fresh beds (FB) treatment (considered as a water saving but not CA technology) and a CT treatment in both rice and maize were also included (Table 2). The plot size for each treatment was at least100 m2 . The number of participant farmers testing alternative tillage options varied from year-to-year. We started with 90 farmers in year 1. Each year, some of the original farmers discontinued the trials due to personal reasons or because they decided to use land for other purposes, while some new farmers showed interest and joined the trials as late-comers. However, 69 farmers maintained trials in all four years, and this group generated all data analysed in this paper. Data from these farmers were grouped into four categories: group 1 with data from 30 farmers who evaluated the CT, ST, RT and PB treatments, group 2 with data from 26 farmers who evaluated CT, ST, FB and PB treatments, group 3 with data from 5 farmers who evaluated CT, ST, FB and RT treatments, and group 4 with data from 8 farmers who evaluated only CT, ST and FB treatments. All farmers (n = 69) maintained CT as a conventional control treatment plot. All treatments for each farmer group were established within the same bounded field for each farmer, with the same farmers continuing from year-to-year. In all non-conventional treatments, farmers used either DSR or non-puddled TPR, depending on the timing and intensity of rainfall. In CT, rice was transplanted on conventionally-tilled flat fields, followed by maize, also flat planted. On FBs, rice seedlings were either manually transplanted, or rice seeds sown directly on the beds, which were later knocked down and reformed by a bed former/planter (see below) for planting of the subsequent maize and rice crop each season. Under the RT treatment, the soil was tilled with a single pass to a depth of 4–5-cm using a 2WT mounted machine, called the power tiller operated seeder (PTOS) with a 400–480 rotor RPM (see below). Directly-sown rice was also established using the PTOS on the flat, or rice seedlings transplanted after one pass in moist soil by the same machine. On PBs, the first rice crop was either manually transplanted or sown directly on fresh beds as described above, but all succeeding crops were established on the same beds after reshaping, without tilling them in, before the sowing of each crop in the sequence. With ST, slots were made by the same PTOS and then rice and maize were sown directly using the fluted roller or inclined plate seed metering device, or rice seedlings were transplanted in the strips. In all the CA-based tillage options (PB, ST, RT), after harvest of rice 15–20-cm anchored residue was retained which was equivalent to 2–2.5 t ha−1 in all farmers’ fields. In case of maize most farmers retained 35–40-cm of stalks but few farmers removed maize stalks for animal feed and fuel. In CT, farmers practiced earthing-up in maize, but not in the alternative tillage options.

89

Table 2 Description of the tillage treatments. Treatment!

Rice†

Maize

CT

2–3 Dry tillage operations by 2 W tractor operated power tiller before rain occurred followed by supplementary irrigation (if no rain) for wet tillage and planking; =∼25-d-old 2–3 rice seedlings transplanted at 20 × 20-cm plant-hill spacing; grown mainly rainfed except supplemental irrigation (if no rain) for land preparation; TPR Same type of dry tillage operations as for CT followed by either DSR sown by power tiller operated bed planter with either fluted roller or inclined plate seed meter; if DSR not feasible due to heavy rain then transplanting of rice seedlings at the edge of the beds Sowing of DSR in a single operation by PTOS with either fluted roller or inclined plate meter at optimum soil moisture, or if DSR not feasible due to heavy rains, then one pass of PTOS followed by TPR In first year, beds prepared as in FB; same beds used for both crops and all years after reshaping but without damaging of the beds before sowing of each crop; either DSR or TPR used depending on the amount and intensity of rain DSR sown with power tiller operated strip-till drill with fluted roller and/or inclined plate seed meter in a single operation followed by light irrigation (if no rains). If heavy rains occurred seedlings transplanted in strips in unpuddled plots; when drills not available, farmers used locally available bamboo sticks to make shallow strips or lines/rows and either used DSR or TPR in strips/lines in untilled/unpuddled condition

Conventional tillage with 2–3 passes prepared by 2 W tractor operated power tiller in residual soil moisture after rice harvest followed by pre-sowing irrigation and then 1–2 passes by power tiller and planking; maize dibbled manually at 60 × 20-cm line-plant spacing at 5–7-cm depth

FB

RT

PB

ST

1–2 Dry tillage after rice harvest followed by maize seeding at 60 × 20-cm line-plant spacing by the bed planter with either fluted roller or inclined plate seed mete; followed by light irrigation in furrows to ensure germination

Seeds sown by using PTOS with fluted roller and/or inclined plate meter at 60 × 20-cm line-plant spacing in a single operation after rice harvest

Same rice beds used for maize planting but beds just reshaped only before sowing of each crop

After harvest of rice, maize seeds sown with residual soil moisture (or with supplemental irrigation if no rain) in strips with strip till drill with fluted roller and/or inclined plate seed meter in a single operation or on lines made by bamboo sticks under untilled condition

2.4. Planting machines used

! CT = conventional tillage; FB = fresh beds; RT = reduced tillage; PB = permanent raised beds; ST = strip tillage. † DSR = direct-seeded rice; TPR = transplanted rice; PTOS = power tiller operated seeder.

2.4.1. Power tiller operated seeder The PTOS is a single-pass shallow-tillage seed and fertilizer drill manufactured in China (model: 2BG-6A) that is commercially sold in Bangladesh. The PTOS is 120-cm wide, allowing six rows of rice at 20-cm spacing, or two rows of maize at 60-cm. Operating capacity is typically 0.14–0.20 ha h−1 (Hossain et al., 2004a). This seeder accomplishes three operations in a single pass, including tillage (up to 5-cm), placement of seed and fertilizer in a furrow, and

seed covering by a post-furrow opener roller bar (Hossain et al., 2004a; Johansen et al., 2012). Compared with traditional broadcast sowing following 2WT full tillage, the PTOS requires about half the time and fuel for sowing cereals, and is sometimes referred to as “reduced tillage” because of shallow seeding and the reduction in number of passes, though the 400–480 rotor RPM speed results in considerable soil surface disturbance (Wohab et al., 2007).

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Table 3 Prices of inputs and outputs and rates used for calculating costs of production and profits in different years for conducting partial economic analysis. Particulars!

2009–2010

2010–2011

2011–2012

2012–2013

Rice sale price (BDT kg−1 ) Maize sale price (BDT kg−1 ) Rice straw price (BDT kg−1 ) Maize stover price (BDT kg−1 ) labour wages (BDT person-day−1 ) Irrigation charges (BDT h−1 ) Maize seed (BDT kg−1 ) Rice seed (BDT kg−1 ) Urea (BDT kg−1 ) TSP (BDT kg−1 ) MoP (BDT kg−1 ) Gypsum (BDT kg−1 ) ZnSO4 (BDT kg−1 ) Borax (BDT kg−1 ) Tillage cost (BDT ha−1 pass−1 ) Machinery seeding cost (BDT ha−1 pass−1 ) Threshing cost (BDT 40 kg grain−1 ) Herbicides¥ Glyphosate (round-up) (BDT L t−1 ) Pendimethalin (Panida) (BDT L t−1 ) Pesticides¥ Fipronil (BDT L t−1 ) Carbosulfan (BDT kg−1 ) Hexaconazole (BDT L t−1 ) Chlorpyrifos (BDT L t−1 ) Imidacloprid (BDT L t−1 ) Carbofuran (BDT kg−1 )

17.2–18.8† 18.8–20 2 0.5 150–180 100 290 45 12 40 25 12 140 170 2000–2500 2500 30–35

17.5 18.8–21.3 2 0.5 150–200 125 190 45 12 22 15 12 140 170 2000–2500 2500 30–40

17.5–18.5 18.8–21.3 2 0.5 200–300 150 290 45 22 24 15 12 140 170 2000–2500 2500 30–52

16.5–17.5 17.5–20 2 0.5 200–300 150 350 45 20 22 15 10 150 170 2500–3000 3000 30–52

! † ¥

840 880

840 880

840 880

1000 1300 900 600 – –

1000 1300 900 600 – –

1000 1100 950 600 2600 120

840–950 880 1150 900 600 2600 120

1 US$ = 77BDT for all particulars. Ranges represent input and output prices/costs in the two districts cross growing season. The herbicides and pesticides listed above are the ones most commonly used by farmers.

2.4.2. Strip till PTOS By removing the half of the PTOS rotary blades, with the curved ends angled towards the slot, this implement can be reoriented towards use for strip tillage. The rotating blades also displace the stubble in front of the furrow openers (Justice et al., 2004), and in some cases specialized blades are used to reduce soil disturbance and to improve better slot coverage (Krupnik et al., 2013). In the strip tillage treatment, slots were formed by removing 24 out of the PTOS’s 48 blades (Hossain et al., 2005), allowing maize seeding in two rows with 4 blades each. In rice, strips were 20-cm apart, necessitating use of six rows created by 4 blades each. 2.4.3. Bed planter Formation of the fresh or the first year of permanent beds by a bed planter entails major soil disturbance. The bed planter is described in detail by Krupnik et al. (2013), but entails single 2WT attachable unit that power tills the soil, places seed and fertilizer by inclined plates and fluted roller systems, respectively, and finally shapes beds by a trapezoidal shaped, rolling bed former. Once beds are established, the seasonal reshaping of beds involves only reshaping of beds with minimal soil disturbance. A 2WT operated bed former/planter, developed jointly by BARI, Cornell Uniersity, and CIMMYT in Bangladesh, and based on CIMMYT models developed in Mexico, can make and shape beds and place seed and fertilizer in furrows on the bed in one pass (Hossain et al., 2004a; Krupnik et al., 2013; Wohab et al., 2009). Beds of 60-cm furrow to furrow (40-cm top-of-bed width) distance are produced which can accommodate two rows of rice and one row of maize. 2.5. Crop management practices 2.5.1. Rice Farmers used a range rice varieties, including both shortduration cultivars (Bina dhan 7, BRRI dhan 33, and 39, etc.) maturing between 105 and 110 days after sowing under direct seeding and

115–120 days under transplanting, and medium-duration varieties (BR 11, BRRI dhan 49, and 52, AC-1, Guti Swarna, etc.) maturing 130–145 days under transplanting. All DSR plots were sown at a rate of 25–30 kg seed ha−1 between 1 and 30 June in each year. Seeds were sown after initial precipitation and when there was sufficient soil moisture for germination. Some farmers opted for dry direct sowing. Here this was the case, a light post-sowing irrigation was applied. Seeds for all TPR plots were sown on seedbeds between 16 and 31 May, either after rainfall or light irrigation. 2–3 seedlings hill−1 were transplanted between 15 June and 15 July. All rice crops were grown under rainfed conditions. Nitrogen, P, K, S, Zn, and B fertilizers rates for rice in the elemental forms were 100, 10, 40, 10, 5 and 0.5 kg ha−1 , respectively, applied as per the recommendation of the Bangladesh Rice Research Institute. In DSR, N was broadcast as urea in 3 equal splits (10 days after seeding (DAS), 25–30 DAS, and 45–50 DAS). In TPR, urea was broadcast twice, at 15–20 days after transplanting (DAT) and 35–40 DAT. All other fertilizers were broadcast basally before tillage in the CT treatment but in all other treatments they were applied in lines basally as triple super phosphate (20% P), muriate of potash (50% K), gypsum (18% S), ZnSO4 (21% Zn), and borax (11% B), respectively, in both DSR and TPR. For both DSR and non-puddled TPR, glyphosate was applied at 1000 × g A.I. in 400 L water ha−1 , between 3 and 7 days before sowing or transplanting using a flat fan nozzle. If rains occurred within 3 h after glyphosate application, the herbicide was reapplied. In DSR, a pre-emergence herbicide, either pendimethalin 1000 × g A.I. or oxadiargyl 90 A.I. ha−1 , was applied in 400 L water ha−1 , at 1–3 days after sowing. A post-emergence herbicide, such as ethoxysulfuron was also applied at 18 and 36 g A.I. in 400 L water ha−1 for broadleaves and sedges, respectively, but only where farmers deemed it necessary. There were no major incidences of pests and diseases; however, whenever any pest or diseases appeared farmers controlled them by applying the pesticides or fungicides shown in Table 3.

M.K. Gathala et al. / Field Crops Research 172 (2015) 85–98

91

Table 4 Effect of alternative tillage options on the agronomic performance of rice, maize and system (4 yr adjusted pooled mean) during 2009–2012 in northwest Bangladesh. Tillage options

CT (69)! FB (39) RT (35) PB (56) ST (69) Sources of variance Year (Yr) Farmer Treatment (Trt) Yr × Trt ! † ¥

Biomass (t ha−1 )

Grain yield (t ha−1 )

HI

Rice

Maize

System

Rice

Maize

System

Rice

Maize

10.06 10.32 9.79 10.07 9.88 Probability 0.097 0.002 0.571 0.171

15.05b† 16.22ab 16.34ab 17.27a 16.02ab

25.12b 26.72ab 26.22ab 27.37a 25.90ab

4.67 4.85 4.63 4.75 4.62

7.79b 8.45ab 8.57ab 9.01a 8.47ab

12.47b 13.36ab 13.22ab 13.76a 13.11ab

0.46 0.47 0.47 0.47 0.47

0.53 0.53 0.53 0.53 0.54

0.123 0.001 0.041 0.251

0.093 0.001 0.038 0.191

0.090 0.004 0.571 0.484

0.118 0.002 0.013 0.356

0.086 0.001 0.013 0.209

0.089 0.009 0.417 0.112

0.270 0.002 0.816 0.391

A value in parenthesis represents the number of replicates (farmers). Within a column, means followed by the same letter are not significantly different at 0.05 level of probability by Tukey’s HST test. CT = conventional tillage; FB = fresh beds; RT = reduced tillage; PB = permanent raised beds; ST = strip tillage.

2.5.2. Maize NK 40, a popular maize hybrid among farmers, was used in all years in both districts. In addition, some farmers in Rangpur opted for one of three other hybrids, including 900 M Gold, Pacific, or Sunshine. Maize was sown between 15 November and 15 December in different years, depending on the time of rice harvest and soil conditions that permitted field access. Nitrogen, P and K fertilizers in maize were applied at elemental rates of 255, 40 and 140 kg ha−1 , respectively, aiming for a yield goal of 12 t ha−1 . Sulfur, B and Zn were applied basally at 30, 5, and 1.4 kg ha−1 , respectively, as per Bangladesh Agriculture Research Institute’s recommendation. All fertilizer sources were the same as in rice. Nitrogen was applied in 3 splits: basally in lines, and broadcast at V6 and V10 stages. Phosphorus was band-placed basally, while K was broadcast 50% basally and 50% at V10. Maize was germinated using residual soil moisture, but in dry years (2009–2010 and 2011–2012) some farmers used a light irrigation before or immediately after sowing. Maize was grown with 2–4 irrigation across seasons, each irrigation providing around 50–60-mm water. Weeds were controlled manually in all treatments except the permanent beds and strip tillage, which made use of the same herbicide practices as those used for DSR. As for rice, there were no major incidences of pests and diseases, and if occurred, they promptly controlled them by applying the available pesticides or fungicides as shown in Table 3. 2.6. Data collection and sampling procedure Grain and straw yields of rice and maize were determined from 10 m2 in the centre of each treatment plot in farmers’ fields. After sun-drying for 2–3 days, total biomass (grain + straw) was weighed with a spring balance. Grains were threshed by hand (rice) or using a small hand-held sheller (maize). Grain yields were reported at a water content of 14% and 15.5% for rice and maize, respectively. Straw yields were reported on air dry weight basis. Harvest index (HI) was calculated as grain yield divided by total biomass yield on a per hectare basis. 2.7. Economic analysis Partial economic analysis for various alternative tillage treatments was conducted by using the variable costs and income from sale of rice and maize grain, and rice straw and maize stover. Variable costs included various input costs, machinery costs and labour use for different treatments (Table 3). Input costs included costs for seed, fertilizers, pesticides, herbicides, and irrigation, while machinery costs included costs for hiring machinery for tillage

and threshers. Labour use included use for operations such as tillage, transplanting/sowing, applications of irrigation, fertilizers and herbicides and pesticides, and for weeding, harvesting and threshing. All input costs were recorded by surveying participating farmers before and end of each crop season, and listed in Bangladesh Taka (BDT) for each year from nearby markets. Since the two districts where on-farm trials were conducted are not far apart from each other, prices of inputs and outputs (grain and straw/stover) did not vary by more than 5% by district or year, and hence were averaged over four years for the two districts. Net income from all treatments was calculated by subtracting expenses for all variable inputs from the calculated gross return. The benefit cost ratio (BCR) was computed as the ratio of gross return and cost of production. Bangladesh Taka was converted to US$ based on a conversion rate of 77 BDT for 1 US$ (www.xe.com). 2.8. Data analysis Because yield and economic data were imbalanced with unequal replications (Tables 4 and 5), they were analysed using a mixed ANOVA model in SAS, separately for rice, maize and the R–M system considering year, replication (farmer), treatment, and their twoand three-way interactions as factors. Since the three-way interactions were not significant they were not shown in the ANOVA (Tables 4 and 5; Fig. 6). Pooled treatment adjusted means were compared by Tukey’s honest significant difference (HSD) at ␣ = 0.05. Adjusted means are statistical averages that have been adjusted or corrected by the model for the imbalances or outliers present in the data sets which otherwise would have an impact on the calculated means. Descending cumulative distribution functions (CDFs) of net profits for various tillage options were constructed for rice, maize, and the R–M system using mean data from the four years. 3. Results 3.1. Effects of alternative tillage options on crop yield, yield variability, and system productivity The ANOVA for the adjusted 4-year pooled mean revealed no significant year (P ≥ 0.05) or treatment × year effects (P ≥ 0.05) for biomass, grain, and HI of rice, maize or the R–M system (Table 4). There were highly significant farmer effects (P ≤ 0.01) for all measured variables, due to the farmers’ fields being scattered over a large area with variable soil and land types. Treatment effects were significant (P ≤ 0.05) for biomass and grain yield of maize, as well as for the R–M system, but not for grain and biomass yield of rice (P ≥ 0.05).

92

M.K. Gathala et al. / Field Crops Research 172 (2015) 85–98

Table 5 Effect of alternative tillage options on partial economics of rice, maize and system (4 yr adjusted pooled mean) during 2009–2012 in northwest Bangladesh. Production cost (US$ ha−1 )

Gross return (US$ ha−1 )

Rice

Maize

System

Rice

Maize

System

Rice

Maize

System

Rice

Maize

System

CT (69)! FB (39) RT (35) PB (56) ST (69)

645 608 607 580 589

1027a† 922b 949ab 954ab 945b

1684 1550 1567 1547 1550

1269 1311 1260 1273 1240

1974b 2120ab 2156ab 2304a 2141ab

3260b 3472ab 3427ab 3592a 3407ab

582 658 614 647 608

945c 1203ab 1204ab 1350a 1201b

1517b 1865a 1820a 1990a 1808a

2.00 2.23 2.18 2.26 2.14

1.90b 2.33a 2.28a 2.43a 2.27a

1.91b 2.21a 2.18a 2.31a 2.18a

Sources of variance Year (Yr) Farmer Treatment (Trt) Yr × Trt

Probability 0.090 0.123 0.001 0.001 0.387 0.037 0.057 0.117

0.087 0.001 0.124 0.032

0.085 0.001 0.516 0.125

0.141 0.003 0.013 0.447

0.091 0.001 0.014 0.253

0.138 0.002 0.692 0.066

0.192 0.003 0.001 0.232

0.149 0.003 0.001 0.243

0.119 0.001 0.412 0.222

0.170 0.002 0.001 0.477

0.151 0.005 0.002 0.045

Tillage options¥

! † ¥

BCR

A value in parenthesis represents the number of replicates (farmers). Within a column, means followed by the same letter are not different at the 0.05 level of probability by Tukey’s HST test. CT = conventional tillage; FB = fresh beds; RT = reduced tillage; PB = permanent raised beds; ST = strip tillage.

3.1.1. Rice Grain yield of rice over four years across the tillage treatments ranged from 4.6 t ha−1 in strip tillage to 4.9 t ha−1 on fresh beds. Biomass yield ranged from 9.8 t ha−1 under reduced tillage to 10.3 t ha−1 on fresh beds, with no significant differences observed for either grain or biomass production. HI of rice was similar (0.46–0.47) across all treatments (Table 4). Box and whisker plots showed highest mean and median yield of rice on permanent beds, with the lowest under reduced tillage (Fig. 4). The inter-quartile range (IQR—a measure of variability, based on dividing a data set into quartiles) was highest for conventional tillage (1.4 t ha−1 ), and lowest for permanent beds (0.9 t ha−1 ), indicating higher variability for the former than the latter. 3.1.2. Maize Maize grain yields over four years ranged from 7.8 t ha−1 with conventional tillage to 9.0 t ha−1 on permanent beds, while biomass yield ranged from 15.1 t ha−1 under the former to 17.3 t ha−1 with the latter (Table 4). For both grain and biomass yield, all three CA-based tillage and crop establishment options and fresh beds treatment were not significantly different from each other, although maize sown on permanent beds performed significantly better than under conventional tillage on the flat. Compared to the latter, the average biomass and grain yield of maize across fresh beds, reduced tillage, and strip tillage, was 7.6 and 9.1% greater, respectively. The HI of maize was not significantly different across the tillage methods, and averaged 0.53. Box and whisker plots for grain yield of maize under the different tillage options showed highest mean yield on the permanent beds, while the highest median yields were found on the permanent beds, reduced tillage, and strip tillage treatments (Fig. 4). The IQR was highest with conventional and strip tillage (each 3.0 t ha−1 ), and lowest for the fresh beds (2.2 t ha−1 ), indicating higher variability in 20

maize yield under conventional and strip tillage compared to fresh bed. 3.1.3. Rice–maize system Because of the lack of significant differences in the aman rice crop, R–M system productivity followed a similar response to maize. Total system-level grain productivity ranged from 12.5 t ha−1 with conventional tillage to 13.8 t ha−1 on permanent beds. System-level biomass productivity ranged from 25.1 t ha−1 in the former to 27.4 t ha−1 with the latter (Table 4). Compared to conventional tillage, average system-level biomass and grain yield across fresh beds, reduced tillage, and strip tillage treatments increased by 4.6 and 6.1%, respectively. Box and whisker plots showed highest mean and median system productivity for the permanent beds, with the lowest under conventional tillage (Fig. 4). IQR was highest for conventional tillage (3.3 t ha−1 ) and lowest for the strip tillage (1.8 t ha−1 ). Other tillage options exhibited intermediate variability. 3.2. Effects of alternative tillage options on partial economics There was no significant year and year × treatment effects for gross return or net income from rice, maize, or the total R–M system. The year × treatment effect was, however, significant for the production cost and BCR at the system level (P ≥ 0.05), but not for individual crops (Table 5). Year effects were also not significant for production cost and BCR. As for yield, farmer-replicate effects were, however, highly significant (P ≤ 0.01) for all the parameters, due to farmer fields being scattered over a large area with variable soil and land types. Further, while treatment effects were not significant (P ≥ 0.05) for all economic parameters in rice, they were significant (P ≤ 0.05) in maize, and except production cost they were significant for all parameters for the total system too.

20

Rice

18

20

Maize

18

12 10 8

16

Grain yield (t ha-1)

Grain yield (t ha-1)

14

14 12 10 8

14 12 10 8 6

6

6

4

4

4

2

2

2

CT

FB

RT

PB

ST

System

18

16

16

Grain yield (t ha-1)

Net income (US$ ha−1 )

CT

FB

RT

PB

ST

CT

FB

RT

PB

ST

Fig. 4. Box and whisker plots showing variability of grain yield of rice, maize and system under different tillage options across 4 years of experimentation in northwest Bangladesh. (CT = conventional tillage; FB = fresh beds; RT = reduced tillage; PB = permanent beds; ST = strip tillage).

M.K. Gathala et al. / Field Crops Research 172 (2015) 85–98 CT

Input cost Labor cost Machinery cost

CT

Input cost Labor cost Machinery cost

Rice

93 CT

Input cost Labor cost Machinery cost

Maize

System 973

672 300

472

235

ST

FB

237

ST

118

702 335 188

109 65 72 63 70

184 333

227 309

FB

150

93 91

183 354

153 710

106

131

ST

1037

685

158 154

100 137

338

RT

PB

FB

178 359 170 320

712 1043

PB

994

227 338

RT

PB

1066 RT

Fig. 5. Cost of production (4 yr mean) under different tillage options for rice, maize and system in northwest Bangladesh (CT = conventional tillage; FB = fresh beds; RT = reduced tillage; PB = permanent beds; ST = strip tillage). Numbers in each spider diagram indicate amount in US$.

3.2.1. Rice There were no significant treatment differences for any of the economic parameters in rice (Table 5). Total costs of production across treatments and years in rice ranged from US $580 ha−1 in permanent beds to US $645 ha−1 in conventional tillage while gross returns ranged from US $1240 in strip tillage to US $1311 in fresh beds (Table 5; Fig. 5). Likewise, net returns ranged from US$582 in conventional tillage to US $658 in fresh beds and the BCR from 2.0 in conventional tillage to 2.3 in permanent beds (Table 5). 3.2.2. Maize In contrast to rice, the results of the economic analysis showed large differences in maize. Maize production cost ranged from US $922 ha−1 with the fresh beds to US $1027 ha−1 for conventional tillage, which required repetitive 2WT passes in the field (Table 5; Fig. 5). Gross returns from maize ranged from US $1974 ha−1 to US $2304 ha−1 while net returns ranged from $945 ha−1 to $1350 ha−1 , and BCR ranged from 1.9 to 2.4 (Table 5). All the economic parameters were significantly different and, except the cost of production, they were lowest for conventional tillage and highest for permanent beds. However, there were no significant differences among the three alternative CA-based tillage options and fresh beds for gross returns and BCR. For net income, strip tillage provided significantly lower returns than the permanent beds but similar to the fresh beds and reduced tillage. BCRs of all the alternative establishment options were similar but were significantly higher than that of the conventional tillage. Compared to conventional tillage, gross returns from the permanent beds and average gross returns across the fresh beds, reduced tillage and strip tillage increased by 16.7 and 8.3%, respectively. Likewise, compared to the conventional tillage, average net income across the fresh beds, reduced tillage and strip tillage increased by 27.3 which further increased to 32.5% when compared across the mean of the fresh beds, reduced tillage and permanent beds. Compared to conventional tillage, average system-level BCR across all other alternative tillage options also increased by 22.5%. 3.2.3. System The cost of production for the R–M system across four years was highest when farmers used conventional tillage (US $1684 ha−1 yr−1 ) and lowest for the fresh beds, permanent beds and strip tillage (each about US $1532 ha−1 yr−1 ). This was due to high labour costs (US $1472 ha−1 yr−1 ) and machinery hiring and earthing-up costs (US$227) for conventional tillage compared to other tillage and crop establishment options (Fig. 5). All other economic parameters (gross return, net return, BCR) for the R–M system were not significantly different for different

tillage treatments but were significantly lower for conventional tillage compared to permanent beds (Table 5). Gross returns across four years for the four alternative crop establishment options were similar (US $3260–3472 ha−1 yr−1 ), with the notable exception of the permanent beds (US $3592 ha−1 yr−1 ) treatments. Net returns was also significantly lower for conventional tillage (US $1517 ha−1 yr−1 ) than all of the alternative tillage options (US $1808–1990 ha−1 yr−1 ), as was BCR for the conventional tillage (1.9) compared to the other treatments (2.2–2.3). Compared to conventional tillage, average system-level gross returns across fresh beds, reduced, and strip tillage was 5.4% greater, while the average system-level net income and BCR across the four alternative establishment options increased by 23.3 and 2.2%, respectively. 3.3. Labour use for rice, maize and system There were no significant yearly differences for labour use for rice, maize, or the R–M system. There were however highly significant farmer and treatment effects (P ≤ 0.01) and significant treatment × year effects (P ≤ 0.05), though no three-way effects, for both crops and at the system level (Fig. 6). For rice, conventional tillage, fresh beds, and strip tillage all required nearly the same amount of labour (67–82 person days ha−1 yr−1 ), though labour used for permanent beds and reduced tillage was lower at about

Fig. 6. Labour use pattern under different tillage options (4 yr adjusted pooled mean) for rice, maize and system in northwest Bangladesh. (CT = conventional tillage; FB = fresh beds; RT = reduced tillage; PB = permanent beds; ST = strip tillage).

94

M.K. Gathala et al. / Field Crops Research 172 (2015) 85–98 120

100

120

Maize

System Labor use (person days ha-1)

Rice

Labor use (person days ha-1)

Labor use (person days ha-1)

120

100

80 60 40 20

80 60 40 20 0

0 CT

FB

RT

PB

ST

100 80 60 40 20 0

CT

FB

RT

PB

ST

CT

FB

RT

PB

ST

Fig. 7. Box and whisker plots showing variability of labour use in rice, maize and system under different tillage options across 4 years of experimentation in northwest Bangladesh. (CT = conventional tillage; FB = fresh beds; RT = reduced tillage; PB = permanent beds; ST = strip tillage).

53 person days ha−1 yr−1 but significantly similar to strip tillage. In case of maize, conventional tillage had significantly higher (73 person days ha−1 yr−1 ) labour use than the four other tillage options (42–44 person days ha−1 yr−1 ) due to more weeding and earthing-up required for the conventional tillage treatment. As with other parameters, labour use followed a generally similar pattern in maize and the R–M system, with significantly higher labour use for conventional tillage (∼154 person days ha−1 ) than the other tillage and crop establishment options (94–114 person days ha−1 ). Compared to conventional tillage, average labour use across the four alternative tillage and crop establishment options decreased by 25%, 40.1%, and 32.6%, respectively, for rice, maize, at the R–M system level. Box and whisker plots for labour use in rice comparing the different tillage methods showed the highest mean and median labour use for conventional and lowest for reduced tillage (Fig. 7). The inter-quarter range (IQR) and the range for lower and upper extremes were smaller for conventional tillage than all other alternative tillage options. The wider dispersion in extreme values for strip tillage show that labour use in this treatment was much more variable compared to other tillage options. For maize, there was less variability in all tillage methods compared to rice, as evident from lower IQRs and narrow extreme values. Variability was conversely highest for reduced tillage compared to other treatments, though conventional tillage had some outliers. System-level labour use followed similar patterns to maize with lower IQRs and narrow extreme values for all tillage options, with the largest variability under reduced tillage. 3.4. Profitability and production risk The probability distributions of profits for individual tillage options were assessed by using descending cumulative distribution functions (CDFs). Descending CDFs describe the potential of obtaining the profits (US $ ha−1 ) greater than a given probability level (0–100%) using data from each farmer. A no-risk, high profit scenario would be shown as a vertical-leaning line placed as far to the right as possible on the abscissa, as demonstrated by Krupnik et al. (2012). For rice, the probability range of obtaining minimum profits spanned from US$ 125 to 1200 ha−1 yr−1 (Fig. 8). At the 60% probability level, consistently higher profit margins were observed with farmers’ use of fresh beds, permanent beds, and reduced tillage (∼US$ 620 ha−1 yr−1 ) compared to conventional tillage (∼US$525 ha−1 yr−1 ). At the 20% probability level, all tillage and crop establishment options exceeded US$ 700 ha−1 yr−1 profit while at the 10% level, ∼US $800 ha−1 yr−1 was obtained. The slope of the lines, however, indicated that there was little difference in the profitability risk profile of any rice establishment option. In case of maize, the profitability range was between US$ 200 and 2450 ha−1 (Fig. 8). Use of descending CDFs can help to improve

investment and production decisions; for example, a farmer who anticipated a minimal profit of US$ 1000 ha−1 yr−1 from permanent beds faced a 95% probability of achieving it. However, farmers interested in obtaining the same level of profitability from strip and conventional tillage, conversely, had only an 80% and 50% probability of obtaining them. CDFs showed that permanent beds provided higher profits in more than 60% of all cases, though the shape of the CDFs indicated that very high profit levels above $2300 ha−1 yr−1 were achievable in only 10% of farmer’s fields. At all probability levels, strip tillage and fresh beds provided intermediate levels of profitability between conventional tillage, permanent beds, and reduced tillage. For the R–M system, annual profits ranged between US $500 and 2900 ha−1 yr−1 across treatments (Fig. 8). Conventional tillage consistently provided the lowest profit (US$500–2300 ha−1 yr−1 ), while permanent beds had the highest profit distribution (US $1000–2900 ha−1 yr−1 ) at all probability levels. Compared to conventional tillage, the permanent beds treatment had a slightly more vertical profit distribution, further indicating increased certainty of obtaining high profits relative to the broader and more gradually sloped conventional tillage curve. Fresh beds and strip tillage provided similar profits and reduced tillage was intermediate between permanent beds and fresh beds or strip tillage at all probability levels, indicating similar risk for obtaining certain level of profit from the fresh beds and the strip tillage. 4. Discussion Increased demand of maize by poultry and fish industries, and as processed food for increasing human population, has resulted in dramatic increase in area under maize and R–M systems over the past 10 years or so in South Asia and Bangladesh. Although their area increase is remarkable, both crops are established with conventional tillage requiring substantial amounts of labour, energy, and water, and raising concerns of system resilience and sustainability. Thus the area increase and practice of conventional tillage warranted for the introduction, evaluation and dissemination of alternative CA-based technologies for the R–M systems to be productive, profitable and sustainable. Substantial experiences, gained particularly from the R–W systems in South Asia, suggest that the CA-based reduced tillage options such as zero or minimum or strip tillage and permanent raised beds can be productive, profitable and sustainable, especially for wheat. Hence, to test the hypothesis that the CA-based tillage options might have similar benefits to the R–M systems too, we evaluated four alternative tillage and crop establishment options for four years in 69 farmers’ fields in Northwest Bangladesh. We observed similar rice yields across all tillage methods, suggesting that the alternative reduced tillage options and fresh beds can be substituted for intensively tilled puddled rice. Maize yields

M.K. Gathala et al. / Field Crops Research 172 (2015) 85–98

CT FB RT PB ST

Descending cumulative probability

100% 90% 80% 70% 60% 50% 40% 30%

Rice

20% 10% 0% 0

500

1000 1500 2000 Profit margin (US$ ha-1)

2500

CT FB RT PB ST

100%

Descending cumulative probability

3000

90% 80% 70% 60% 50% 40% 30% 20%

Maize

10% 0% 0

500

1000 1500 2000 Profit margin (US$ ha-1)

2500

CT FB RT PB ST

100%

Descending cumulative probability

3000

90% 80% 70% 60% 50% 40% 30% 20%

System

10% 0% 0

500

1000 1500 2000 Profit margin (US$ ha-1)

2500

3000

Fig. 8. Descending cumulative probability for profit margins for rice, maize and system under different tillage options (4 yr mean) in northwest Bangladesh. (CT = conventional tillage; FB = fresh beds; RT = reduced tillage; PB = permanent beds; ST = strip tillage).

and total system productivity were similar across all the CA-based tillage options and fresh beds, though those resulting from permanent beds planting were significantly different and greater than under conventional tillage. Maize yields under the different tillage options were less variable than rice yields because rice was mostly grown under rainfed condition, with variable precipitation regimes resulting in different soil moisture levels, while maize, being a dry season crop, was grown entirely using irrigation, which stabilizes yield. Due to higher maize yield under CA-based reduced tillage methods and fresh beds, the system productivity also resulted similarly to maize. We suggest that maize areas under different CAbased reduced tillage options could be extended in Bangladesh but particularly cultivation under permanent beds could be promoted

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to farmers by discouraging the current practice of growing maize under the conventional tillage. This would require policy interventions for promotion of permanent beds as well as conducting more farmer-participatory on-farm trials and demonstrations and trainings to farmers and local stakeholders such as from GOs, NGOs and private sector. Development and on-farm evaluation of small-scale machinery such as bed formers/planters would also be required for wider acceptance by, and promotion to, farmers. Our results showed no significant differences in rice yield between strip tillage and conventional tillage. These findings are similar to Bhushan et al., 2007 but are different from Saharawat et al. (2010) and Gathala et al. (2013), studies that were conducted on lighter soils and low rainfall areas in the Northwestern IGP. Saharawat et al. (2010) found decrease in, but Gathala et al. (2013) recorded an increase in, rice yield under zero-tilled direct seeded, compared to conventionally-tilled puddled transplanted, conditions. In contrast, we observed no significant differences, whether direct-seeded or transplanted under fresh or permanent beds, compared to the conventionally tilled treatments with sowing under flat conditions. This result was also different from some studies in R–W systems on fresh or permanent beds (Bhushan et al., 2007; Choudhury et al., 2006; Gathala et al., 2011a,b; Kukal et al., 2010; Yadvinder-Singh et al., 2009). Each of these studies which were conducted in Northwest IGP reported lower rice yield under fresh or permanent beds compared to conventionally-tilled puddled condition. On the other hand, a few other studies (Jat et al., 2014; Lauren et al., 2008; Talukder et al., 2008), in the Eastern IGP reported higher rice yield under permanent beds than under conventional tillage on flats. Lauren et al. (2008) also found that rice on permanent beds was more responsive to increasing nitrogen rates than under conventional tillage in rice–wheat–mungbean (Vigna radiata) sequences in Northwest Bangladesh. All the above studies in which rice yields were lower on permanent beds were conducted on the light soils in Punjab, and in Western Uttar Pradesh in the Northwestern IGP without any retention of rice or wheat residue. In those studies, researchers noted that beds constructed using light soils eroded and eventually flattened after some rainfall and irrigation events. They also noted weeds, and in some cases nematodes infestation and Fe deficiency, especially for DSR on beds, which may explain yield decline. Moreover, Yadvinder-Singh et al. (2009) and Kukal et al. (2008, 2010) used 4-WT with wide wheel width which compacted the beds formed on light soils, a problem we did not observe in this study that employed smaller width 2WT tires. Choudhury et al. (2006) also observed that rice planted on the edges of the raised beds did not compensate for the loss in rows through increased tillering or leaf growth at the edges of the rows, hence resulting in a loss in solar radiation interception by the crop, and a loss in yield. However, in the studies by Gathala et al. (2011a,b) and Jat et al. (2014), which were also conducted on light soils, no bed erosion or flattening, nor Fe deficiency was observed, and so yields did not decrease on permanent beds. Our results for higher maize yield and higher system productivity under permanent beds than the conventional tillage were similar to those of Talukder et al. (2008) and Singh et al. (2010) from Northeast IGP, who also observed higher maize yields and the R–M system productivity when planted on permanent beds than under conventional tillage. Our results for similar maize yield with strip and conventional tillage were similar to Krupnik et al. (2014a) who observed no consistent differences between these tillage treatments in on-station trials. In the current study, as well as in Krupnik et al. (2014a), maize was planted on roughly the same day under each treatment. However, because maize yield declines with late planting (Timsina et al., 2011), earlier establishment with strip tillage may prove advantageous. Conversely, Krupnik et al. (2014b) found large differences between conventional and strip tillage across years and

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locations in detailed, multi-location and on-farm, farmer-managed but researcher backed studies in southern Bangladesh, in which farmers were able to establish their crops roughly 5–7 days earlier by forgoing multiple passes under conventional land preparation. In the present study, the cost of production for rice was highest under conventional tillage and lowest under permanent beds and strip tillage. Net income and the BCR, however, were similar for all tillage and establishment options. Of all the costs required for growing rice, consumable input costs (e.g., fertilizers, herbicides, etc.) were the largest. Reduced tillage required the highest ($354 ha−1 ) and conventional tillage and fresh beds required the lowest input costs (∼$304 ha−1 ) in rice. Labour costs and machinery costs, however, were highest for conventional tillage (total $344 ha−1 ) compared to the alternative tillage and establishment options (Fig. 5). There were sometimes more weeds under reduced tillage compared to the fresh beds and conventional tillage, requiring the application of herbicides. Likewise, more labour was used for land preparation, puddling and transplanting in rice, and irrigation applications, etc. under conventional tillage, which typically required 4–6 tillage operations before transplanting. This required more machinery costs compared to other tillage methods. In our trials, both TPR and DSR were used in all alternative tillage and crop establishment treatments, but where farmers opt for DSR on flats or beds, then considerable amount of labour savings would be possible (Kumar and Ladha, 2011). The cost of production for maize was also highest under conventional tillage ($1027 ha−1 ), primarily due to increased labour and machinery costs, and was not significantly different between other tillage and establishment options. As with rice, there were more weed problems in maize planted using reduced tillage and, consequently, more herbicide costs (Fig. 5). Labour use for rice under conventional and strip tillage, and also fresh beds, was modestly higher than under the permanent beds and reduced tillage treatments. Since strip tillage is a relatively new practice in Bangladesh, some participating farmers did not follow the precise package of the recommended cultivation practices for DSR using strip tillage–particularly with respect to the even application of chemical weed control. This resulted in increased variability among the farmers’ plots for this treatment, although with time and experience, farmers interested in use of strip tillage are likely to learn how to best manage this tillage option, potentially decreasing yield variability. In maize, the reduction in labour use for all the alternative tillage options is largely attributable to machine sowing and the elimination of the need for of earthing-up while in the conventional tillage maize always required earthing-up and hence required more labour. Profitability distributions for each individual tillage option were assessed by using descending cumulative distribution functions. Considering rice, there was higher probability of obtaining consistently higher profit margins from all alternative tillage options compared to conventional tillage, except below the 30% certainty level around US$ 675 ha−1 , indicating relative advantages of the alternative tillage options at low and more intermediate profitability levels. In case of maize, though permanent beds provided higher profits in more than 60% cases, profits were similar to the reduced tillage treatment in about 30% cases, and at all probability levels above 5%, strip tillage and fresh beds provided intermediate profits between conventional tillage, permanent beds, and reduced tillage. For the R–M system also, conventional tillage consistently showed the lowest profit probability distribution, with a more gentle slope than the alternative tillage and establishment options. These results indicate the general superiority of CA-based tillage and establishment options in reducing the risk of lower profits, until the 5% or lower level, where reduced tillage, strip tillage and permanent beds treatments levelled off at between US$ 2300 and 2750 ha−1 . Of the alternative tillage options, permanent beds had the highest profit at

all probability levels above 5% certainty, indicating the amelioration of production risk. To obtain full benefits from strip or reduced tillage with sowing either on flat fields or beds, the retentionof an economicallyrational level of the previous’ crops residues as a mulch can improve moisture availability, nutrient cycling, soil structure over time in rice-based cropping systems (Yadvinder-Singh et al., 2005). Rational residue retention can also shift soil microbial populations towards those more beneficial to crop growth (Govaerts et al., 2007). While puddling and conventional tillage is traditionally practiced for flooded rice, which reduces weed problems and potential for floodwater loss to percolation, it can also maintain the soil organic matter (SOM) and soil nutrient supplying (SNS) capacity (Buresh et al., 2008; Witt et al., 2000). Diversification from R–R to R–M cropping sequences with conventional tillage in maize, with or without residues can adversely affect SOM and SNS capacity in Asia’s soils (Pampolino et al., 2006; Witt et al., 2000). However, if maize is grown under reduced or no tillage with residue retention – even in the case of permanent beds – then both SOM and SNS capacity can be maintained (Govaerts et al., 2006, 2007; Witt et al., 2000). This was perhaps the reason why the studies conducted in the Northwestern IGP (e.g., Kukal et al., 2010; Yadvinder-Singh et al., 2009) had no benefits to rice on permanent beds over the conventional tillage with flat planting, as none of those studies retained residue of different crops. Moreover, as mentioned above, Yadvinder-Singh et al. (2009) and Kukal et al. (2010) used larger tractor tire size width and hence may have compacted the beds formed on light soils. In contrast, Talukder et al. (2008) and Lauren et al. (2008) both found that, on permanent beds formed with 2WTs, straw mulch significantly increased rice yields after only one to two cropping cycles in Nepal and Bangladesh even though those beds were constructed on light soils. Talukder et al. retained 50–100% residue of all crops in the rice–wheat–maize system, which helped reduce N rate and observed significant yield benefits to all crops on permanent beds over conventional tillage with flat planting. Permanent beds with residue retention can also provide benefits in terms of increased yield and profits, reduced costs and water requirements, and improved soil physical properties, has been observed for cotton–wheat systems (Das et al., 2014), maize–wheat systems (Hari Ram et al., 2011; Jat et al., 2013), soybean–wheat systems (Hari Ram et al., 2013), and R–W systems (Gathala et al., 2013; Jat et al., 2014), all in Northwestern IGP. However, farmers in Bangladesh manage mixed-farm enterprises, of which livestock compose an important component. In cases where large amounts of residues are left in the field, competition between components of the farm – particularly crops and the livestock which farmers rely on during the dry season – could take place, limiting the uptake of mulching as a practice where farmers are unable to produce sufficient biomass to satisfy both crop field and animal needs (Valbuena et al., 2012). The current study considered the former. In our on-farm trials, some farmers (n = 25) harvested maize leaves for animal fodder prior to sampling of grain and biomass yields. In rice, most farmers retained partial (15–20cm anchored) residues but in maize some farmers kept 30–40 cm stalk, and preferentially allocated them as feed for their livestock and fuel. Further research is needed to place cropping systems into the context of the larger farm enterprise systems that farmers manage, to seek methods to optimize productivity while minimizing trade-offs with livestock. Such trade-offs should be assessed for their contribution to income and increased food and nutritional security from milk and meat production. Finally, an important issue with CA-based tillage and crop establishment systems is the potential for shifts in the composition of weed communities and need for appropriate weed management strategies for such systems (Chauhan et al., 2012; Kumar et al., 2013a). For example, Chhokar et al. (2007) found that although

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zero tillage can lower the incidence of Phalaris minor infestation in wheat, others (Chhokar et al., 2007; Chauhan et al., 2012) reported that other kinds of weeds such as Rumex dentatus L. would proliferate in untilled systems. Some evidence, however, does suggest that weed pressure reduces over time as farmers continue to practice CA (Muoni et al., 2014). These factors imply that farmers moving from conventional to reduced tillage systems will need to be sensitive in terms of the need for careful pre-planting weed control measures. Careless control measures can later result in excess labour to rouge weeds that were not killed by pre- and post-emergent herbicides, as was observed for the strip tillage treatment in this study. Further on-farm research is required to thoroughly evaluate weed community dynamics as farmers shift from R–R to R–M systems – especially where some form of reduced tillage is employed – in Bangladesh. 5. Conclusions We conclude that while the alternative tillage and crop establishment options tested in this study had no significant yield advantage over the conventional tillage in rice, they resulted in significant advantages in terms of reduced production cost and labour use, and therefore resulted in increases in farmer incomes. In maize, while most alternative tillage and establishment options provided yield benefits similar to conventional tillage, maize planted on permanent beds exhibited a significant yield advantage over conventional tillage. On a system basis also, permanent beds exhibited a significant yield advantage over conventional tillage. Considering our assessment of the profitability distributions and risk analysis, we conclude that both rice and maize planted sequentially on permanent beds and strip tillage can result in higher net income and BCR compared to conventional tillage practices. As such, permanent beds planting may prove to be advantageous where farmers shift from R–R to R–M systems of Bangladesh, by assuring higher potential for income generation from field cropping systems without reductions in total system productivity. The challenge, however, is to increase farmer awareness and acceptance of permanent raised bed and strip tillage planting systems, as they call for radical changes in land preparation, sowing, weed and water management practices. Further research is needed to determine what types of farmers permanent beds may be most appropriate for, as well as to parse out which biophysical and socioeconomic conditions are prerequisite for adoption and implementation of this practice. Acknowledgements This research was conducted under the Sustainable Intensification for Rice–Maize Production Systems in Bangladesh project (CIM-2007-122) funded by the Australian Centre for International Agricultural Research (ACIAR). The contents and opinions expressed herein are those of the author(s) and do not necessarily reflect the views of ACIAR. We wish to thank all our national collaborators (BARI, BRRI and RDRS) who assisted us in successfully completing this study, and all the participating farmers who persistently and enthusiastically collaborated in this study. References Ali, M.Y., Waddington, S.R., Hodson, D., Timsina, J., Dixon, J., 2008. Maize-Rice Cropping Systems in Bangladesh: Status and Research Opportunities. CIMMYT–IRRI Joint Publication, Mexico, pp. 36. Aryal, J.P., Sapkota, T.B., Jat, M.L., Bishnoi, D.K., 2014. On-farm economic and environmental impact of zero-tillage wheat: a case of northwest India. Exp. Agric., 1–16, http://dx.doi.org/10.1017/S001447971400012X. Bänziger, M., Edmeades, G.O., Beck, D., Bellon, M., 2000. Breeding for Drought and Nitrogen Stress Tolerance in Maize: From Theory to Practice. CIMMYT, Mexico D.F., pp. 1–69.

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