Energy comparison of two rice cultivation systems

Renewable and Sustainable Energy Reviews 42 (2015) 666–671

Contents lists available at ScienceDirect

Renewable and Sustainable Energy Reviews journal homepage: www.elsevier.com/locate/rser

Letter to the Editor

Energy comparison of two rice cultivation systems Hamdollah Eskandari n, Sajjad Attar Department of Agriculture, University of Payame-Noor, Tehran, Iran

art ic l e i nf o

a b s t r a c t

Article history: Received 9 July 2014

The current experiment, conducted in Ramhormoz, Iran, compared the energy consumption of two rice cultivation systems: direct seeded rice and transplanting cultivation systems. In the transplanting system, rice is grown by hand-transplanting thirty-day-old nursery seedlings into standing water in the main field. The direct cultivation system has no nursery or tillage operation. Instead, rice is cultivated in the main field using a cereal seeder. In this study, data was collected from 185 rice producers, 125 of whom used transplanting and 60 of whom used direct seeding as their rice growing system. The results indicated that the energy input of the two cultivation systems was significantly different in the use of diesel fuel, pesticide, electricity, irrigation, human labor, and total energy. Herbicide usage was higher in the direct seeding system than in the transplanting system, but other energy inputs were found to be higher in the transplanting system. The energy output of the transplanting system was higher than that of the direct seeding system. The energy input of the direct seeding system was lower than that of the transplanting system, resulting in a higher energy ratio, which suggests that the direct seeding system would increase energy efficiency and sustainability in rice production. & 2014 Elsevier Ltd. All rights reserved.

Keywords: Energy Human labor Transplanting rice Direct seeded rice

Contents 1. Introduction . . . . . . . . . 2. Materials and methods 3. Results and discussion. 4. Conclusion . . . . . . . . . . References . . . . . . . . . . . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

1. Introduction Energy is considered to be fundamental in national development and providing critical services for humans. Per criteria, energy consumption is introduced as a factor for evaluating the social and economical development of a country [18,22]. In developing countries, energy consumption is greatly increased by economical development [8]. Population increase, limited arable lands, and rising living standards result in increased energy inputted into agricultural systems to maximize yield production n

Corresponding author. E-mail address: [email protected] (H. Eskandari).

http://dx.doi.org/10.1016/j.rser.2014.10.050 1364-0321/& 2014 Elsevier Ltd. All rights reserved.

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

666 667 669 670 671

and minimize cultivation operations carried out with human intervention [24]. The increase of energy consumption is higher in agriculture than in other economical sectors due to mechanized cultivation operations and the utilization of soil nutritive materials, particularly fertilizers [14]. Agricultural fields are, in fact, energy consuming ecosystems, and the amount of energy consumed depends on the level of mechanization [18]. There is concern that in coming years, agriculture will not be able to meet the demands for food of humans and domesticated animals. Additionally, high energy consumption in agriculture will compromise food security for future generations [9]. Thus, the efficient utilization of energy resources is of high importance for sustainable improvement.

H. Eskandari, S. Attar / Renewable and Sustainable Energy Reviews 42 (2015) 666–671

In Ramhormoz, Iran, rice, the third most important crop after wheat and maize, is grown in two different cultivation systems, transplanting and direct seeding systems. In the transplanting system, rice is grown by transplanting seedlings from the nursery into standing water in the main field. High amounts of water loss are expected because of the puddling process, surface evaporation, and percolation and result in high energy consumption for irrigating the rice plants [5]. Transplanting operations are usually performed by human labor. Direct seeded rice has no nursery, and seeds are sown directly into the main field. This cultivation system avoids puddling and maintains continuous moist soil conditions; therefore, the overall water demand is reduced. The direct seeding system is more mechanized than the transplanting system. Admittedly, it has been remarked that productivity is often lower in the direct seeding cultivation system than in the transplanting system [23]. In order to save water and labor and to promote conservation agriculture through energy conservation, the hypothesis that transplanting can be replaced with the direct seeding system needs more investigation. Finite resources of nonrenewable energies clarify the necessity for optimal energy utilization. Thus, this research was aimed to analyze the energy use and relationship between the energy inputs and outputs of two rice production systems in order to introduce the most energy efficient system.

2. Materials and methods This research was carried out during the 2011–2012 growing season in Ramhormoz, Iran (461360 N, 311160 E, altitude 150 m a.s. l). The soil texture of the experimental site was silt loam. The research field was located in a semi-arid region, where summers are hot and dry and winters are cool and rainy. In order to attain an overview of energy consumption in rice production, the energy consumption of two rice cultivation systems, direct seeding and transplanting, were compared during all cultivation stages. Data was collected from 185 rice producers (125 used transplanting and 60 used direct seeding). The total number of rice producers in the experimental site was 350 (240 transplanters and 110 direct producers). The sample size was determined using Eq. (1) [1]:
2 2 Nt s i n¼h ð1Þ 2 Nd þt 2 s2 where n is the required sample size, N is the number of rice producers (statistical community), s2 is the variance of the trait, t is the coefficient of confidence in normal distribution (considered to be 1.96), and d is the difference between actual ratio of the trait in the community and the estimation (0.05 was considered the maximum difference). The collected data were obtained from two sources including farmers and direct observations of fields. The farmers were asked to provide the accurate information about their rice production systems with completing the questionnaires. The type of used machineries, technical specification of machineries including motor capacity and diesel fuel consumption, total land area, planting and harvesting method, crop yield per unit area, irrigation method, irrigation duration, water flow rate, number of workers, the amount of seed, type and amount of fertilizer and pesticides were asked in the questionnaires. During cultivation period, the recent information was checked again with direct views of fields. Energy consumed by machinery in the field was calculated as follows: EM ¼

½E  M  T  N

ð2Þ

667

Table 1 Energy equivalent of input and output of rice production system. System input

Energy equivalent

Unit

Refs.

Rice seed Rice residue Machineries Diesel fuel Nitrogen fertilizer (N) Phosphorus fertilizer (P2O5) Potassium fertilizer (K2O) Liquid herbicides Solid herbicides Human labor (men) Human labor (women) Electricity

14.70 12.50 62.50 56.30 66.14 12.44 11.15 102.00 120.00 1.96 1.57 3.6

MJ kg  1 MJ kg  1 MJ kg  1 MJ l  1 MJ kg  1 MJ kg  1 MJ kg  1 MJ l  1 MJ kg  1 MJ h  1 MJ h  1 MJ kw  1

[6] [6] [22] [26] [16] [16] [16] [7] [7] [1] [1] [6]

where EM (MJ ha  1) is energy consumed by machinery, E (MJ kg  1) is energy of machinery (per unit), M (kg) is weight of machinery, T (h ha  1) is time of machinery usage (hour) and N is efficient lifetime of machinery (h). The mean of fuel consumed by diesel machinery (tractor or combine) per hour was calculated using the following equation [11]: MF ¼

C Ë

a  P pto

ð3Þ

in which MF is the mean of the fuel consumed by diesel motor (l ha  1); á is the 0.223 l hp-h; Ppto is the power of P.T.O. used in cultivation operations (hp). Fuel consumption (l ha  1) was calculated by multiplying Eq. (2) with machinery work time (h ha  1) and, as a result, energy consumption (MJ ha  1) was achieved by multiplying consumed fuel by the energy equivalent of fuel (Table 1). Crop irrigation resulted in direct and indirect consumption of energy. Indirect consumed energy, known as energy of irrigation, included energy consumed for dam building, production of raw materials, and the production and transportation of all factors relating to crop irrigation. Since the precise calculation of these energy related factors is difficult, 20% of direct energy was considered to be indirect energy. Energy used for pumping water was considered to be direct energy. The power needed for pumping water was achieved using the equation:
 λQ h P¼ ð4Þ 1000  em  ep where P (w) is consumed power, λ (N m  3) is water density, Q (m3 s  1) is the flow rate of the water pump, h (m) is total dynamic charge, and em and ep are motor and pump efficiency, respectively. Energy consumption of the water pump (kW ha  1) was calculated by multiplying Eq. (4) by total irrigation time (hour) per hectare and then dividing by one thousand. In order to change the unit of water pump energy consumption into MJ ha  1, it was multiplied by 3.6 (Table 1). Based on the energy equivalents of input and output (Table 1), energy consumption of the two rice cultivation systems was calculated for the two states of utilization and no utilization of straw using the following equations [12]: Energy ratio ¼

energy output energy input

ð5Þ

yield produced ðrice outputÞ energy input

ð6Þ

Net output energy ¼ energy output  energy input

ð7Þ

Energy productivity ¼

668

H. Eskandari, S. Attar / Renewable and Sustainable Energy Reviews 42 (2015) 666–671

Fig. 1. Mean comparison of energy of used inputs in two rice cultivation systems. Means of machineries, seeds and fertilizer was not significantly difference; other traits were seen to be different between two rice cultivation systems at 0.01 probability level.

H. Eskandari, S. Attar / Renewable and Sustainable Energy Reviews 42 (2015) 666–671

669

Fig. 2. Mean comparison of energy indices of rice cultivation systems with straw utilization. The difference of energy ratio between two cultivation systems was significant at Pr 0.01. Net output energy and energy productivity was not significantly different between transplanting and direct seeding cultivation systems.

The data were subjected to statistical analysis of variance and means were compared using t-student test. SPSS (ver.13) was used as the statistical software.

3. Results and discussion Based on the analysis of variance, other than machinery, seed, and fertilizer, the two rice cultivation systems had significantly different values for energy consumption. Use of diesel fuel, electricity, irrigation, and human labor and total energy consumption were higher in the transplanting system, but more energy was consumed for herbicides in the direct seeding cultivation system (Fig. 1). The transplanting system consumed more diesel fuel. Since the direct seeding system had no rice nursery tillage operation or nursery field preparation, less diesel fuel was consumed compared to the transplanting system. Furthermore, the main field was prepared in the form of transplantation plots in the transplanting system and strip borders in the direct seeding system. Therefore, an additional farm boundary is needed in the transplanting system which increases diesel fuel consumption, and so field preparation is a high energy consuming operation [7]. These results are compatible with the findings of Mohammadi et al. [20] and Karimi et al [15]. However, tillage system has a high effect on energy consumption. Baruaha and Duttab [4] concluded that more than 50% of energy consumption in rice production was related to the tillage system. They also reported that the amount of energy consumption during field preparation has no significant effect on crop grain yield. Thus, revising tillage system for increasing energy efficiency can be attained without reducing grain yield. Water logging the crop growing environment in the transplanting system caused an anaerobic condition which limited weed growth. It has been reported that weeds grow more in direct

seeded rice than in transplanted rice [3,7,13]. Since the application of herbicides is reported to be an effective way to suppress weeds and provide the direct seeded rice a weed-free environment [10], higher herbicide use was needed in the direct seeding system and resulted in higher energy consumption. The higher electric energy consumption in the transplanting system was related to water consumption and irrigation. In the transplanting system, rice seedlings were grown in puddled and flooded soil conditions. In such conditions, high losses of water may occur through the puddling process, surface evaporation, and percolation. Much water is therefore needed in the transplanting system, and the consumption of electric energy used for pumping water for longer periods of time is increased. The direct seeded rice cultivation system, which had an every-other-day irrigation regime (eight hours per day) is an appropriate method for increasing energy consumption efficiency in rice fields because it reduces water demands up to 45% compared to transplanting systems. Irrigation considerable energy consumption is allocated to the irrigation, where reducing energy consumption of irrigation results in increasing energy efficiency in rice production [17]. Using surface water resources instead of groundwater resources is an effective way for reducing energy consumption by reducing electricity and diesel fuel required for supplying water for rice growing [19]. All seedling establishment operations (sowing in nursery and transplanting seedlings from nursery to main field) in the transplanting system were performed using human labor. Thus, it is logical that rice production in the transplanting system uses large amounts of human energy. In general, human labor is negatively related to the degree of mechanization of a cultivation system, because the more mechanized farm needs less human labor [2]. The transplanting system exerts high working and financial pressures on rice growers during a short period of 10–20 days, so farmers are inclined to use the direct seeding system [21].

670

H. Eskandari, S. Attar / Renewable and Sustainable Energy Reviews 42 (2015) 666–671

Fig. 3. Mean comparison of energy indices of rice cultivation systems without straw utilization. The difference of energy ratio and net output energy between two cultivation systems was significant at P r0.01. Energy productivity was not significantly different between transplanting and direct seeding cultivation systems.

On the other hand, heavy use of human labor is one of the main obstacles of the transplanting system [22] because it results in low efficiency. Therefore, the extension of direct seeded rice can be a useful method for reducing energy consumption. Although Sidhu and Chandra [25] reported that increasing mechanization resulted in increasing energy consumption, the result of the current research showed that reducing human labor (increasing mechanization) did not result in energy efficiency decreasing. Payman et al. [23] findings are compatible with results of current research where increasing mechanization increased energy efficiency of rice production. This was due to the lower energy consumption of direct seeding system during seed planting and seedling establishment. When straw was utilized, the total energy output (grain and straw) of the transplanting system was 114720 MJ ha  1 and of the direct seeding system was 98677 MJ ha  1 (with a grain yield of 3429 kg ha  1 and straw weight of 5144 kg ha  1 for the transplanting system and grain yield of 2950 kg ha  1 and straw weight of 4425 kg ha  1 for the direct seeded rice). The mean of total energy efficiency (energy ratio) in the direct seeding and transplanting systems were 2.85 and 2.30, respectively (Fig. 2). Although total energy output of the transplanting system was higher than that of the direct seeding system because of lower grain production of the recent cultivation system (480 kg ha  1), the energy ratio was observed to be higher in the direct seeded rice. This result was achieved because energy input of the direct seeding cultivation system was lower than that of the transplanting system, resulting in a higher energy ratio of the direct seeding system. Similarly, even though a higher grain yield was obtained with the transplanting system, the energy ratio of the direct seeded rice was seen to be higher, because the energy input of the direct seeding system was as much as 15500 MJ ha  1 lower than that of the transplanting system. These results are compatible with the findings of Nasiri and Singh [21] who reported that reducing cultivation operations in the direct seeded cultivation of

rice resulted in a higher energy ratio compared to the transplanting system. Energy productivity was not significantly different between the two cultivation systems, and net output energy was different only when straw was not utilized (Fig. 3). This result indicates that energy is more efficiently attained from grain in the direct seeded rice system.

4. Conclusion The highest proportion of energy consumption in direct seeding and transplanting rice cultivation systems belonged to electric energy consumed for pumping water. Appropriate field leveling (for example, using a laser leveler) and the use of efficient irrigation systems, i.e. sprinkle and trickle irrigation, are effective solutions for reducing electricity and water energy consumption. Changing traditional tillage systems into a conservational tillage system is an effective factor in decreasing diesel fuel energy consumption because of the resulting decrease in tillage operations, change in irrigation methods, and reduction in human labor. Since the direct seeding rice cultivation system was most effective in reducing energy consumption, appropriate management of input to increase the efficiency of the systems is supposed to be needed. It seems that for optimizing energy consumption in rice production systems, farmers should be taught to reduce unnecessary energy consumption, makes it indispensable that use of machineries, fertilizers and other inputs must be monitored by agricultural experts. Furthermore, increasing farmer’s knowledge about non-chemical weeds control is one of the most important ways for reducing energy consumption in the context of herbicides. Despite all advantages of direct seeding systems in reducing energy consumption, supporting farmers for increasing rice grain yield under this cultivation system, will encourage them for more using such energy efficient producing system.

H. Eskandari, S. Attar / Renewable and Sustainable Energy Reviews 42 (2015) 666–671

References [1] Alam MS, Alam MR, Islam KK. Energy flow in agriculture: Bangladesh. Am J Environ Sci 2005;1(3):213–20. [2] Bartlett JE, Kotrlik JW, Higgins CC. Organizational research: determining appropriate sample size in survey research. Inf Technol Learn Perform J 2001;19(1):43–50. [3] Baruah DC, Boa GC. Energy demand forecast for mechanized agriculture in rural India. Energy Policy 2008;36:2628–39. [4] Baruaha DC, Duttab PK. An investigation into the energy use in relation to yield of rice in Assam, India. Agric Ecosyst Environ 2007;120:185–91. [5] Begum M, Juraimi AS, Amartalingam R, Man BA, Rastans Bin-Syed SO. The effects of sowing depth and flooding on the emergence, survival, and growth of Fimbristylis miliacea (L.) Vahl. Weed Biol Manage 2006;6:157–64. [6] Bockari-Gevao SM, Van-Ishak W I, Azmi Y, Chan CW. Analysis of energy consumption in low land rice based copping system of Malaysia. J Sci Technol 2005;7(4):819–26. [7] Canakci M, Topakci M, Akinci I, Ozmerzi A. Energy use pattern of some field cops and vegetable production: case study for Antalya region, Turkey. Energy Convers Manage 2005;46:655–66. [8] Chaudhary VP, Gangwar B, Pandey DK, Gangwar GS. Energy auditing of diversified rice-wheat cropping systems in indo-gangetic plains. Energy 2009;34(9):1091–6. [9] Chauhan B, Johnson D. Ecological studies on Cyperus difformis, Cyperus iria and Fimbristylis miliacea: three troublesome annual sedge weeds of rice. Ann Appl Biol 2009;155:103–12. [10] Confori P, Giampieto M. Fossil energy use in agriculture: an international comparison. Agric Ecosyst Environ 1997;65:231–43. [11] Diknann DI. Silviculture and biology of short rotation woody crops in temperate regions then and now. Biomass Bioenergy 2008;30:696–705. [12] Gitsopoulos TK, Froud-Williams RJ. Effects of oxadiargyl on direct-seeded rice and Echinochloa crus-galli under aerobic and anaerobic conditions. Weed Res 2004;44:329–34.

671

[13] Grisso RD, Kocher MF, Vaughan DH. Predicting tractor fuel consumption. Appl Eng Agric 2004;20(5):553–61. [14] Kamoshita A, Ikeda H, Yamagishi J, Ouk M. Ecophysiological study on weed seed banks and weeds in Cambodian paddy fields with contrasting water availability. Weed Biol Manage 2010;10:261–72. [15] Karimi M, Rajabpour A, Tabatabaeefar A, Borghei A. Energy analysis of sugarcane production in plant farms: a case study in Debel Khazaie agroindustry in Ian. Am-Euras J Agric Envion Sci 2008;4(2):165–71. [16] Karkacier O, Goktolgu ZG. Input–output analysis of energy use in agriculture. Energy Convers Manage 2005;46:1513–21. [17] Kengejy A, All ET. Irrigation energy efficient of farming system and rice production. Energy Convers Manage 2005;53:65–72. [18] Kitania O. Handbook of agricultural engineering. Energy and biomass engineering. ASAE Publication; 1998. [19] Larson R, Feargmir P. Optimization of energy input for rice cop in irrigations system. Energy Convers Manage 2001;35:45–9. [20] Mohammadi A, Tabatabaeefar A, Shahin-Rafiee S, Keyhani A. Energy use and economical analysis of potato production in Iran: a case study Adabil province. Energy Convers Manage 2008;79:3566–70. [21] Nassiri SM, Singh S. Study on energy use efficiency for paddy crop using data envelopment analysis (DEA) technique. Biosyst Eng 2008:1320–5. [22] Ozkan B, Akcaoz H, Fert C. Energy input–output analysis in Turkish agriculture. Renewable Energy 2004;29:39–51. [23] Payman M, Roomi R, Alizadeh M. Determination of enegy consumption of traditional and mechanized rice production. Iran J Agric Eng Res 2005;22:67–80 (English Abstract). [24] Shao H, Chu L. Resource evaluation of typical energy plants and possible functional zone planning in china. Biomass Bioenergy 2008;32:283–8. [25] Singh G, Chandra H. Production and economic factors growth in Indian agriculture. Technical bulletin No. CIAE.2002.91, Central institute of agricultural engineering. NABI Bagh. Berasia Road, Bhopal. India. [26] Singh JM. On farm energy use pattern in different cropping system in Haryana. MS thesis. University of Flensburg. Germany; 2002.