Received 14 June 2015; accepted 30 June 2015; published 6 July 2015

ABSTRACT

Rice (Oryza sativa L.) in the dry season (Boro) followed by rice in the wet season (Aman) is the major cereal cropping system in Bangladesh. The average productivity (7 Mg∙ha⁻¹) of this system is far below attainable yields (14 Mg∙ha⁻¹) in farmers’ fields, resulting in a large yield gap mainly due to farmers’ traditional management practices. Narrowing yield gap is a vital complementary strategy in improving rice yield and consequently enhancing food security. We evaluated BRRI recommended management practices, BRRI recommended management practices along with two N management options (leaf color chart and Urea Super Granule) and farmers’ crop management practices integrated with quality seed, leaf color chart (LCC) and Urea Super Granule (USG) in farmers’ fields of Kapasia, Gazipur over 6 contiguous seasons during 2009-2012. Across years, all the management options increased grain yields compared with the farmers’ practice (FP) by 1.12 Mg∙ha⁻¹ in Aman and 0.84 Mg∙ha⁻¹ in Boro season. The higher yield response (43%) occurred with BRRI recommended management practices followed by BRRI recommended management practices in combination with Urea Super Granule (42%) as N source (BRRI-USG). Yield advantage of 41% could be attained by BRRI recommended management practices with leaf color chart (LCC) aided N management (BRRI-LCC) while this was 22%, 13% and 13% higher than FP (farmer’s practice) when only quality seeds, USG and LCC were used with farmers’ management practice. BRRI Rec., BRRI-LCC and BRRI-USG∙management options reduce the yield gap of FP by 41%, with an average of 2.87 Mg∙ha⁻¹. When farmers adopted FP-QS, FP-USG and FP-LCC management options, they reduced the yield gap of FP by 21%, 13% and 12%, with an average of 1.49, 0.88 and 0.81 Mg∙ha⁻¹, respectively. The average added net returns with BRRI Rec., BRRI-LCC and BRRI-USG∙ma- nagement options were US$175 to US$362 ha⁻¹ in the wet season and US $158 to US $263 ha⁻¹ in the dry season. BRRI management practices and BRRI management practices integrated with two N management options, either LCC or USG has the potential to boost rice yield and consequently total rice production in Bangladesh.

Keywords:

Rice-Rice Cropping System, Yield Gap, Productivity, Net Profit

Subject Area: Agricultural Science

1. Introduction

About half of the world’s cereal production and 89% of the world’s harvested rice are from Asia [1] . Economically disadvantaged people spend as much as 30% - 40% of their income just to buy rice [2] . Increasing the amount of rice production and keeping the rice price low and affordable to them are crucial for poverty reduction. Rice yield must continue to increase at an annual rate of 1.5% compared with the current rate of 0.8% to keep pace with the expected demand [3] . Like in many other Asian countries, rice is the staple food in Bangladesh and it contributes one-half of the agricultural GDP and 55% of the total labor employment [4] . During the last 20 years, Bangladesh has increased rice production 1.8 times with almost no increase in its land area of about 11.7 million ha [5] . However, because of the continuous increase in population growth, rice demand in 2050 is projected to be 56% higher than in 2001 [6] . This is going to be doubly challenging in light of the diversion of better quality land, water, and labor to other sectors of the national economy. Evidence is now appearing that the productivity of rice-rice and rice-wheat systems is plateauing because of a fatigued natural resource base [7] [8] . The productivity and sustainability of rice-based cropping systems are threatened because of i) the inefficient use of fertilizer, water, and labor; ii) increasing scarcity of water and labor; iii) changing climate; iv) emerging energy crisis and rising fuel prices; v) emerging socioeconomic changes such as urbanization, migration of labor, and preference for nonagricultural work [9] . In addition, recent increases in the prices of farm inputs in relation to outputs, fewer off-farm work opportunities for supplementing farm income, reduced remittances from relatives working outside villages, and declining income and purchasing power of poor consumers have threatened the existence of rice producers and consumers [9] .

Bangladesh produced about 50.1 million tons of rough rice from 11.7 m ha of land in 2010 with a productivity of 4.3 t∙ha⁻¹ [5] . The present productivity is far below the attainable yield of 8 - 10 t∙ha⁻¹ in the dry season (Boro) and 5 - 6 t∙ha⁻¹ in the wet season (Transplanted Aman) in farmers’ field experiments [10] - [13] . This difference in yield in farmers’ fields between farmer-managed and researcher-managed trials exists because the best available production technologies are not adopted in farmers’ fields. This could be, among others, due to farmers’ characteristics (e.g., lack of knowledge and skills, and risk aversion), farm characteristics (e.g., poor soil, difficult terrain, and inaccessibility), and inappropriateness of the technology to farmers’ circumstances (e.g., labor- intensive, high investment costs, and poor access to inputs). However, a large portion of this yield gap remains unexplained.

Minimizing the yield gap and increasing profit and product quality are becoming increasingly difficult to achieve by using a single-technology-centric approach. The use of a component technology in isolation also has limited widespread adoption. Combining and simultaneously applying a number of the best compatible individual or component technologies are crucial for maximizing overall benefits to farmers [9] . Depending on the need and profitability of new technologies, farmers generally integrate new technology with the cultural practices being practiced by them on their farms. The choice or selection of the best individual or component technologies in an integrated manner is crucial for achieving the full benefit. As narrowing yield gap of rice is attributed to many factors, it should be better quantified and understood. This paper aims to evaluate the contribution of different crop management factors in curtailing the rice yield gap over six seasons during three years.

2. Materials and Methods

2.1. Experimental Sites and Seasons

On-farm trials were conducted in a continuous rice-rice cropping system for six consecutive seasons during 2009-2012 at Moison village in Kapasia Upazila (24˚12'N and 90˚36'E) of Gazipur District. The farmers which represent common cropping systems, management practices, land types and soil types were selected (Figure 1). The climate of the area is subtropical, characterized by wide seasonal variations in rainfall, high temperatures and humidity. Weather data were collected from a nearby weather station of Bangladesh Meteorological Department. The weather pattern during the study period is given in Figure 2 and Figure 3.

Moison village in Gazipur District belong to Agro-Ecological Zone (AEZ) 28 (Madhupur Tract). The soils are well drained friable clay loam to clay or heavy clay, strongly acidic, mainly phosphate fixing, low in P, K, S, and B in AEZ-28 [14] . Transplanted rice was grown on puddled soil under rainfed conditions in the wet season or Aman (June-July to November-December) and under irrigated conditions in the dry season or Boro (December-January to April-May). In both seasons, soils were well prepared through 4 - 5 passes with a power tiller followed by 2 - 3 ladderings. High-yielding semi-dwarf rice cultivars BRRI dhan49 (135 day seed to seed) and BRRI dhan28 (140 day seed to seed) were grown in the Aman and Boro seasons, respectively.

2.2. Experimental Design and Treatments

The trials were established in farmers’ fields in a randomized complete block design with a set of seven treatments in each farmer’s field. Farmers’ fields were considered as replications. The number of replicate farmers was twenty. There were seven treatments, viz. farmers’ management practices (FP), farmers’ management prac-

tices with quality seed (FP-QS), farmers’ management practices with USG (FP-USG), farmers’ management practices with LCC based N management (FP-LCC), Bangladesh Rice Research Institute (BRRI) recommended management practices coupled with leaf color chart (LCC)-aided fertilizer N management (BRRI-LCC), BRRI recommended management practices coupled with urea super granules (USG) as source of fertilizer N (BRRI- USG) and BRRI recommended management practices (BRRI Rec.).

2.3. Treatment Details

2.3.1. Farmers’ Management Practices (FP)

The farmers’ management practice of seed and seedling raising, planting∙method, and fertilization varied considerably among farmers and seasons (Table 1). All farmers used seeds from their own source having 80% - 85% germination capacity without any seed treatment. They prepared a flat seedbed without any organic matter and used a very high seed rate (140 - 168 g∙m⁻²) on the seedbed. Five to nine rice seedlings (35- - 44-day-old) per hill in Aman and five to eight rice seedlings (48- - 60-day-old) in the Boro season were transplanted at random spacing.

Across seasons and years, all farmers applied N fertilizer at early tillering, late tillering and panicle initiation stage. Farmers applied on an average 70% - 76% of N fertilizer between early tillering and late tillering (Table 1). In the Aman season, 100% farmers applied P and K fertilizer but no farmer applied S and Zn fertilizer. In the Boro season, 100% of the farmers applied P fertilizer, 100% applied K fertilizer, 80% - 100% applied S fertilizer, and 40% - 60% applied Zn fertilizer.

^aMean ± standard deviation (S.D.). All reported means for timing and amount of fertilizers are based on farmers applying fertilizers.

2.3.2. Farmers’ Practices with Quality Seed (FP-QS)

The management practices in FP-QS were same as FP except seed source. Certified seed from BRRI having 92-95% germination capacity was used.

2.3.3. Farmers’ Practices with USG (FP-USG)

The management practices in FP-USG were same as FP except N fertilizer management. Nitrogen as USG was deep-placed within 7 - 10 DAT at 7 - 10 cm soil depth at the rate of one USG (1.8 g) in Aman and one USG (2.7 g) in Boro in the middle of 4 hills. The total N dose was 54 kg∙ha⁻¹ in Aman and 79 kg∙ha⁻¹ in Boro.

2.3.4. Farmers’ Practices with LCC (FP-LCC)

The management practices in FP-LCC were same as FP except N fertilizer management. Nitrogen as urea was applied by using the LCC in a real-time N management approach [15] . The N rate varied among farmers’ fields and seasons. The mean total N dose ranged from 77 to 103 kg∙ha⁻¹ in Aman and from 93 to 124 kg∙ha⁻¹ in Boro (Table 2).

2.3.5. BRRI Recommended Management Practices with LCC (BRRI-LCC)

A set of five BRRI recommended management practices integrated with existing farmers’ practices were i) certified seeds, ii) healthy young seedlings, iii) hill spacing of 20 cm × 20 cm at transplanting with 3 - 4 seedlings per hill, iv) AEZ-based recommended P, K, S, and Zn fertilization, and v) N application by using the LCC in a real-time N management approach. The management practices recommended by BRRI were used for raising healthy seedlings (Table 3) [16] . Across the years, seedling age ranged from 28 to 34 days in Aman and from 40 to 48 days in Boro. The P, K, S, and Zn fertilizers were applied at the rates and time recommended by BRRI based on AEZ-based recommendations [16] . Nitrogen as urea was applied by using the LCC in a real-time N management approach [15] . The N rate varied among farmers’ fields and seasons. The mean total N dose ranged from 77 to 103 kg∙ha⁻¹ in Aman and from 93 to 124 kg∙ha⁻¹ in Boro (Table 3).

2.3.6. BRRI Recommended Management Practices with USG (BRRI-USG)

The management practices in BRRI-USG were same as BRRI-LCC except N fertilizer management. Nitrogen as USG was deep-placed within 7 - 10 DAT at 7 - 10-cm soil depth at the rate of one USG (1.8 g) in Aman and one USG (2.7 g) in Boro in the middle of 4 hills. The total N dose was 54 kg∙ha⁻¹ in Aman and 79 kg∙ha⁻¹ in Boro.

2.3.7. BRRI Recommended Management Practices (BRRI Rec.)

The management practices in BRRI were same as BRRI-LCC except N fertilizer management. The total N dose was 54 kg∙ha⁻¹ in Aman and 79 kg∙ha⁻¹ in Boro. Nitrogen was applied as urea in three equal splits: 7 - 10, 25 - 30 and 35 - 40 days after transplanting (DAT) in Aman and at 15 - 20, 30 - 35 and 40 - 45 DAT in Boro.

2.4. Data Collection and Analysis

Grain yields (rough rice) were obtained from two central 6 m² harvest areas in each plot at∙harvestable maturity and reported at 0.14 g H₂O g⁻¹ fresh weight of grain. Human labor used for seedling raising, transplanting, and fertilizer application and wage rate were recorded. The time required to complete each field operation was expressed as person-days ha⁻¹, considering 8 h to be equivalent to 1 person-day. The farm-gate price of rough rice and prices of seed, fertilizers, and seed-treating chemicals were also recorded.

^aS.D., standard deviation of the mean.

^aS.D., standard deviation of the mean.

Analysis of variance (ANOVA) of the treatment means were compared using Least Significant Difference (LSD) at the 5% level of probability [17] . Descriptive statistics such as means, standard deviation, range, 25% quartile, and 75% quartile were used to determine the variability of parameters.

Treatments were evaluated based on added net return relative to the farmers’ practice, which is the difference between added gross return and added cost for a treatment as compared with FP. Added gross return equaled additional yield as rough rice (yield of treatment−yield of FP) multiplied by the price of yield. Added cost equaled the sum of costs for differences in labor determined as [(labor for seedling raising, transplanting, and fertilizer application of the treatment-labor for seedling raising, transplanting, and fertilizer application of FP) × wage rate] and costs for differences in fertilizer and seed-treating chemicals determined as (fertilizer and seed-treating chemical costs of treatment-fertilizer and seed-treating chemical costs of FP). The prices of seeds, cowdung, fertilizer, seed-treating chemical, rough rice, and labor wage were as follows: seed = US $0.45 kg⁻¹, cowdung = US $12.86 to 19.29 Mg⁻¹, P fertilizer = US $0.28 to 0.51 kg⁻¹ P, K fertilizer = US $0.19 to 0.45 kg⁻¹ K, S fertilizer = US $0.06 to 0.08 kg⁻¹ S, Zn fertilizer = US $1.29 to 1.54 kg⁻¹ Zn, urea = US $0.15 to 0.26 kg⁻¹

N, USG = US $0.21 to 0.29 kg⁻¹ N, seed-treating chemical = US $34.07 to 35.48 kg⁻¹, rough rice = US $0.22 to 0.26 kg⁻¹, and labor wage = US $1.93 to 2.57 person-day⁻¹ (US $1 = Bangladesh Taka 77.78).

3. Results and Discussion

3.1. Grain Yield

BRRI management practices and BRRI management practices along with two N management options, either LCC or USG, had a significant response in rice grain yield in both Aman and Boro seasons in all three years (Table 4 and Table 5). Famers’ management practices when coupled with either quality seed, LCC or USG also showed significant increase in grain yields compared to farmers’ practices. The yields of BRRI-LCC, BRRI- USG and BRRI recommended practices were always similar in the range 4.29 - 4.84 Mg∙ha⁻¹ in Aman and in 5.12 - 5.50 Mg∙ha⁻¹ Boro. BRRI recommended practices produced the highest yield in Aman 2009, 2011 and in Boro 2011-12. BRRI-USG produced the highest yield in Aman 2010 and in Boro 2010-11 and BRRI-LCC in Boro 2009-10.

BRRI-LCC, BRRI-USG and BRRI recommended practices turned out about 41% - 62% in wet and 27% - 38% higher grain yield in dry season, respectively. The results of the study also implies that yield advantage of 13% - 35% in wet season and 1% - 21% in dry season could be attained when only quality seeds, USG and LCC were used with farmers’ management practice. On average, the yields in Boro were 18% higher than the yields in Aman, with the highest yield of 5.50 Mg∙ha⁻¹ in Boro and 4.84 Mg∙ha⁻¹ in Aman.

Figure in parenthesis indicates yield increase in percent over farmers practice

Irrespective of years, the average yield for the system (combined yield of Aman and Boro seasons within a cropping year) for FP was 7.04 Mg∙ha⁻¹. The system productivity of FP-QS, FP-USG and FP-LCC, BRRI-LCC, BRRI-USG and BRRI Recommended management options was 8.53, 7.92, 7.85, 9.84, 9.91and 9.99 Mg∙ha⁻¹. BRRI-reported that average attainable yield for this system is 14 Mg∙ha⁻¹ [10] - [13] . When farmers adopted BRRI Rec., BRRI-LCC and BRRI-USG∙management options (9.91 Mg∙ha⁻¹) resulting a yield gap of 4.09 Mg∙ha⁻¹. On the other hand, system productivity of FP-QS, FP-USG and FP-LCC management options was 8.10 Mg∙ha⁻¹ resulted in a yield gap of 5.90 Mg∙ha⁻¹. Thus, in this study, BRRI Rec., BRRI-LCC and BRRI-USG

NS, ^*, ^** for not significant, significant at 5 and 1% level, respectively.

NS, ^*, ^** for not significant, significant at 5 and 1% level, respectively.

management options reduced the yield gap of the farmers’ practice by 2.87 Mg∙ha⁻¹. Results also revealed that famers can able to trim down the existing gap by 1.49, 0.88 and 0.81 Mg∙ha⁻¹ when only quality seeds, USG and LCC were used with farmers’ management practice. The higher positive response of BRRI-LCC, BRRI-USG and BRRI recommended practices was due to the combined effects of certified seeds with seed treatment, healthy seedlings, optimum planting density, balanced fertilization, and better synchronization of N fertilization with plant needs. These findings suggest potential to increase farmers’ rice yields through BRRI recommended practices in an integrated way. Other studies in India and Bangladesh rice fields also reported comparatively higher yields in the range 0.8 - 2.0 Mg∙ha⁻¹ with the use of improved methods of more than one crop production factor in an integrated way [18] - [20] .

Box and whisker plots showed higher mean and median yield of wet and dry season rice on BRRI-LCC, BRRI-USG and BRRI Rec. treatments, with the lowest under farmers’ practice (Figure 4). The inter-quartile range (IQR―a measure of variability, based on dividing a data set into quartiles) was higher in wet season rice and lower in dry season rice, indicating higher variability in the former than the latter.

In wet season, Box and whisker plots for grain yields under BRRI-LCC, BRRI-USG and BRRI Rec. treatments showed higher variability than the other treatments. High variation in rainfall and maximum temperature during the study period may have the contribution in higher grain yield variability (Figure 2 and Figure 3). Whereas, BRRI-LCC, BRRI-USG and BRRI Rec. treatments showed lower variability in dry season rice. Lower variability of dry season rice yield may be the consequence of lower variation in minimum and maximum temperature in dry seasons (Figure 3). A similar observation was reported by [21] who examines the relationship between the yield of three major rice crops (e.g., Aus, Aman and Boro) and three main climate variables (e.g., maximum temperature, minimum temperature and rainfall) for Bangladesh.

3.2. Economic Analysis

Added costs and added net returns for different management options relative to the FP were used to assess profitability for the use of different management practices (Table 6). The average added costs for BRRI recommended management option and BRRI recommended management practices along with two N management options in Aman and Boro across years ranged from $92 to 124 ha⁻¹ and from $75 to 114 ha⁻¹, respectively. The

added costs associated with BRRI management practices involved treatments in at least 75% of the farmers’ fields were ≥$94 - 123 ha⁻¹ in Aman and ≥$77 - 114 ha⁻¹ in Boro. These added costs for BRRI Rec., BRRI- LCC and BRRI-USG∙management options were mainly because of the additional application of P, K, Zn and additional labor requirement with these management options. The large ranges in added costs suggest substantial variation in the amounts of additional P, K, Zn and labor use.

The average added costs for FP-QS in Aman and Boro across years was $13ha⁻¹. The average added costs for FP-USG in Aman and Boro across years ranged from $31 to 49 ha⁻¹ and from $33 to 49 ha⁻¹, respectively. The added costs associated with FP-USG in at least 75% of the farmers’ fields were ≥$33 - 46 ha⁻¹ in Aman and ≥ $35 - 49 ha⁻¹ in Boro. This cost for FP-USG was mainly because of the additional labor requirement with USG placement. FP-LCC management option did not impose any additional cost both in Boro and Aman across years except in Aman, 2011.

The average added net returns with BRRI recommended management option and BRRI recommended management practices along with two N management options were always positive, ranging from US $175 to 362 ha⁻¹ in Aman and from US$159 to 265 ha⁻¹ in Boro across years. The added net returns associated with BRRI- LCC, BRRI-USG and BRRI recommended practices in at least 75% of the farmers’ fields were ≥$305 to 440 ha⁻¹ in Aman and ≥$196 to 324 ha⁻¹ in Boro (Table 6). The average added net return was highest with BRRI recommended management practice compared with other treatments in both seasons across three years. The average added net returns were higher with BRRI-LCC than with BRRI-USG in both seasons, suggesting LCC-aided N management as a more profitable option than USG. The average added net return with FP-QS was ranging from US $ 146 to 233 ha⁻¹ in Aman and from US$101 to 177 ha⁻¹ in Boro across years. The added net returns associated with FP-QS in at least 75% of the farmers’ fields were ≥$187 to 267 ha⁻¹ in Aman and ≥$121 to 324 ha⁻¹ in Boro. The average added net return with FP-LCC was ranging from US$ 96 to 173 ha⁻¹ in Aman and from US $37 to 60 ha⁻¹ in Boro across years. The added net returns associated with FP-LCC in at least 75% of the farmers’ fields were ≥$147 to 224 ha⁻¹ in Aman and ≥$51 to 67 ha⁻¹ in Boro. FP-USG resulted average added net return ranging from US $42 to 159 ha⁻¹ in Aman and from US $24 to 76 ha⁻¹ in Boro across years. The negative added net returns with FP-USG in at least 25% of the farmers’ fields were mainly due to high added costs ($34 - 46 ha⁻¹) compared with added returns from increased yield (0.04 - 0.39 Mg∙ha⁻¹) in Aman 2011, Boro 2010-11, and Boro 2011-12. The large ranges in added net returns ($115 to 662 ha⁻¹) indicate large farm-to-farm variability in the costs and gains associated with inputs and outputs for using BMP along with either LCC or USG across seasons and years (Table 6).

In Aman season, on an average per dollar net return (added net return divided by added cost) was highest in BRRI recommended management practices ($ 2.84) followed by BRRI-LCC ($ 2.70). But in Boro season, it was highest in BRRI-LCC ($ 2.54) followed by BRRI recommended management practices ($2.40). The results suggested that BRRI recommended management practices and BRRI-LCC were more profitable option compared to others.

The higher positive added net returns with the use of BRRI-LCC, BRRI-USG and BRRI recommended management practices in the majority of farmers’ fields confirmed that they are ready for wide-scale evaluation and promotion in Bangladesh. Our results suggest that BRRI recommended management practices and BRRI recommended management practices along with either LCC or USG can be promoted through integration with the farmers’ own portfolio of practices for increased profitability. The markedly increased yield and profit for rice in Bangladesh reported in another study [19] arise from the use of LCC-based N management combined with improved management of other nutrients and improved weed control.

4. Conclusion

Efficient and judicious integration of improved crop management practices along with the farmers’ management practices has scope to increase rice production in Bangladesh. About 27% - 62% grain yield increases with BRRI-LCC, BRRI-USG and BRRI recommended management practices resulting in farmers’ net profit increase of US $158 to 362 ha⁻¹. Adoption of BRRI-LCC, BRRI-USG and BRRI recommended management practices in an integrated way can be a measure to attain productivity through minimizing yield gap. A massive and effective program for wider demonstration, refinement, and dissemination of BRRI-LCC, BRRI-USG and BRRI recommended management practices in an integrated way throughout the country may be taken to improve the productivity and profit from rice farming.

5. Limitation of the Study

Although the selected fields were in same ecosystem, soil physical and chemical properties analysis might assist in better interpretation of the findings.

Cite this paper

Md. Khairul Quais,Md. Mahbubur Rahman Dewan,Amina Khatun,Hasina Sultana, (2015) Rice Yield Gap Minimization in Central Bangladesh: Using and Adapting Existing Technologies. Open Access Library Journal,02,1-13. doi: 10.4236/oalib.1101641

References

NOTES

^*Corresponding author.