Campbell, C.A.

Zentner, R.P.

English

eCommons@USASK

An energy evaluation of crop rotations in southwestern Saskatchewan

University of Saskatchewan

University of Saskatchewan Research Archive

- 183 -AN ENERGY EVALUATION OF CROP ROTATIONS IN SOUTHWESTERN SASKATCHEWAN R.P. ZENTNER and C.A. CAMPBELL Research Station, Research Branch, Agriculture Swift Current, Saskatchewan. INTRODUCTION Canada, S9H 3X2 The Swift Current Research Station's long-term crop rotation experiment, established in 1966, is undergoing detailed evalua·tion. Papers that summarize yield and grain protein considerations (Campbell et al. 1983b), nitrate-N distribution in the soil and N uptake by the plants (Campbell et al. 1983a), bicarbonate-P distribution in the soil and P uptake by the plants (Campbell et al. 1984a), and economic returns (Zentner et al. 1984) have been completed. In this paper, the energy considerations of the 12 crop rotations included in the experiment are discussed. Inputs of non-renewable energy, energy output, net energy produced, and energy efficiency levels of the crop rotations are exam-ined and compared using data collected over the period 1967 to 1978. MATERIALS, METHODS, AND ASSUMPTIONS Twelve crop rotations considered potentially suitable for south-western Saskatchewan (Table 1) were established in 1966 on 81 plots (each 0.04 ha in size) in a three-replicate experiment. Prior to the experiment, the area had been in a fallow-wheat rotation since 1922. The soil was a Wood Mountain loam (Orthic Brown Chernozem). Stubble-mulch tillage techniques, with commercially available equipment, were used in the management of the rotations. An average of 3.3 tillage operations (ranging from 2 to 5 operations) with a heavy-duty cultivator and/or rodweeder, plus a late fall application of 2,4-D ester herbicide, were required to control weeds on summerfallow areas. On cropped areas, seedbed preparation generally consisted of one opera-tion with a heavy-duty cultivator with rodweeder attachment. The plots were seeded with a hoe-press drill at the recommended rates of 67, 31, 63, and 76 kg/ha for spring wheat, flax, fall rye, and oats, respective-ly. Seeding took place generally in early May, except for rye which was usually sown in the first week of September. Ammonium nitrate fertili-zer (i.e., 34-0-0) was broadcast prior to seeding and monoammonium phos-phate fertilizer (i.e., 11-48-0) was placed with the seed according to treatment specifications (Table 1) and in accordance with the general recommendations of the Saskatchewan Soil Testing Laboratory. Herbicides (i.e., bromoxynil and MCPA, 2,4-D ester, triallate, diclofop methyl, and glyphosate) were applied as required for in-crop weed control using recommended methods and rates. The continuous-type rotations generally received more N fertilizer and more herbicides than the less intensive crop rotations. Rotation number 1 2 3 4 5 6 7 8 9+ 11 12 - 184 -Table 1. Crop rotations and treatments Rotation Fallow-wheat-wheat Fallow-wheat-wheat Fallow-flax-wheat Fallow-fall rye-wheat Fallow-wheat-wheat Oat hay-wheat-wheat Flax-wheat-wheat Continuous wheat Continuous wheat Continuous wheat Fallow-wheat Continuous wheat Comments P applied, but no N applied N and P applied N and P applied N and P applied N applied, but no P applied N and P applied N and P applied N and P applied [fallow if less than 60 em of moist soil at planting time, otherwise crop] N and P applied (fallow if grassy weeds become a problem, otherwise crop] N and P applied N and P applied P applied, but no N applied + Rotations 9 and 10 were necessary for fallowing 12-year study period. cropped continuously because (see comments) did not occur the criteria during the Plots were harvested at the full ripe stage, except for oat hay. Each plot was windrowed and the grain yields determined by threshing the seed with a conventional combine. The straw and plant residue were distributed back on the plots by a paddle-type spreader attachment on the combine. Oat hay was cut at the soft dough stage and dried natur-ally, baled, and weighed. After harvest, all seeded plots received an application of 2,4-D ester herbicide at the recommended rate to control winter annual weeds. Information on the type and frequency of field operations per-formed, machines and equipment used, types and amounts of herbicides and fertilizers applied, and crop yields obtained in the experiment for each rotation treatment, replicate, and year were used as input data for the energy evaluation. Fuel use asociated with the field operations was not measured in the experiment. Estimates were made using empirical rela-tionships that relate fuel use to power requirements of the specific machines (Zentner et al. 1983). Recommended depths of tillage (where appropriate) and forward speeds were assumed for all field operations. The physical quanities of inputs used in production were converted to energy values using energy coefficients taken from the literature (Table 2). Both direct and indirect energy expenditures were included. Energy invested in machinery and in grain and machine storage buildings (including maintenance and depreciation) was amortized over the expected useful life of the capital items (Jensen 1977). No allowance was made for the energy removed from the soil in the form of plant nutrients, nor - 185 -for that which was captured directly from the sun by the plants. Fur-thermore, no allowance was made for home or personal energy consumption. Table 2. Energy coefficients for agricultural inputs and outputs Agricultural input/output Variable inputs Gasoline Diesel Lubricants Nitrogen fertilizer Phosphorus fertilizer Bromoxynil and MCPA 2,4-D ester Triallate Diclofop methyl Glyphosate Fixed inputs Powered machines Non-powered machines Trucks Grain storage bldgs. Machine storage bldg. Outputs Wheat Fall rye Flax Oats Oat hay'i= Energy coeff. 41.2 45.2 43.8 89.1 15.6 295.0 202.0 231.0 328.0 461.0 9.9 6.8 11.0 13.8 153 .,0 13.8 14.0 9.2 10.4 0. 73 Unit of meas. MJ/L MJ/L MJ/L MJ/kg MJ/kg MJ/kg of MJ/kg of MJ/kg of MJ/kg of MJ/kg of MJ/kg/yr MJ/kg/yr MJ/k~/yr MJ/m /yr MJ/m2/yr MJ/kg MJ/kg MJ/kg MJ/kg MJ/kg Data Source Southwell and Rothwell (1977) Southwell and Rothwell (1977) Southwell and Rothwell (1977) Leach (1976) Leach (1976) Art Boerma et al. (1980) AI Boerma et al. (1980) AI Boerma et al. (1980) AI Boerma et al. (1980) AI Boerma et al. (1980) Jensen (1977) Jensen ( 1977) Jensen (1977) Jensen (1977) Jensen (1977) Southwell and Rothwell (1977) Southwell and Rothwell 0977) Southwell and Rothwell (1977) Southwell and Rothwell (1977) Southwell and Rothwell (1977) t AI = Active ingredient * Oat hay was converted to total metabolizable energy for humans at the rate of 7.261 MJ/kg of beef produced and a feed conversion ratio of 10:1. For all crops except oat hay, energy output was taken to be the total metabolizable energy of the grain (less seed requirements) for human consumption (Table 2). No allowances were made for the straw and crop residue products because of the need to return them to the land to maintain soil productivity and to provide protection against soil erosion. Oat hay was assumed to be an input to beef production which was subsequently slaughtered for human consumption. A feed conversion ratio for oat hay of 10:1 was assumed for the beef animals (National Academy of Sciences 1970). The energy content of the oat seed was also subtracted from the energy output of the oat hay production system. - 186 -Each rotation was evaluated in terms of total and selected cate-gor1es of energy inputs, energy output, net energy produced (i.e., energy output minus energy input), and energy output/input ratios. Rotations 9 and 10 were treated as additional replicates of rotation 8 because the criteria necessary for fallowing did not occur during the 12-yr study period (Table 1). The results are reported on a per unit of cultivated land basis and include adjustments for the proportions of crop and sumerfallow in the rotations. RESULTS AND DISCUSSION Energy Inputs Total input of non-renewable energy increased as the proportion of summerfallow in the rotation decreased (Table 3). The continuous wheat rotation receiving recommended rates of N and P fertilizer had the highest energy requirement, while the traditional 2-yr fallow-wheat rotation had the lowest. The continuous-type rotations with N and P fertilizer applied required about twice the energy input as for the fallow-wheat rotation. The 3-yr rotations with N and P fertilizers applied required from 11 to 26% more energy than that required for the fallow-wheat rotation. Rotation number 1 2 3 4 5 6 7 8,9,10 11 12 Table 3. Total non-renewable energy input Fertilizer t Rotation N p F-W-W 0 .; F-W-W .; .; F-Flx-W .; .; F-Rye-W .; .; F-W-W .; 0 O(hay)-W-W .; .; Flx-W-W .; .; Contin.W .; .; F-W .; .; Contin. W 0 .; energy input 3249c 376Sbc 3937b 346Sbc 3492bc 6130a 59 58 a 6413a 3132c 4292b Standard deviation MJ/ha - - -211 401 641 374 693 2097 1914 2224 240 1067 Index of§ mean energy input 104 120 126 111 112 195 190 205 100 137 t I indicates the application of recommended rates of N or P fertilizer. Oindicates no application of N or P fertilizer. *Means followed by the same letter do not differ (P <.OS). §The mean energy input for the fallow-wheat rotation was used as the index base (i.e., index= 100). Substituting flax, fall rye, or oat hay for wheat in the 3-yr and 1n the continuous-type rotations did not significantly change the total energy requirements of the respective rotations. Total energy requirements were reduced by about 14 and 33% when no N fertilizer was applied to the 3-yr and continuous wheat rotations, respectively. - 187 -Similarly, failure to apply P fertil:i.zer to the ~-yr wheat rotation reduced the total energy requirement by about 7%. The annual variation in total energy inputs was highest for the continuous-type rotations and lowest for the 2-yr wheat rotation and for the 3-yr wheat rotation receiving only P fertilizer. Fuel (including lubricants) and fertilizers were the major energy inputs of the rotations (Table 4). Fuel use did not differ greatly among the rotations. This occurred because as the proportion of summer-fallow in the rotation declined, the savings in fuel from the reduced summerfallow activities was offset by the increased fuel requirements for planting and harvesting of the additional cropped area. Energy expenditures for fuel represented from 28% of the total energy input for the well-fertilized continuous wheat rotation to 53% for the fallow-wheat rotation. Table 4. Energy input by resource categoryt Rotation Fert. Fuel & Capital number Rotation N p lubricants Fertilizers Herbicides items MJ7ha % MJ7ha % MJ7ha % MJ7ha ' % 1 F-W-W 0 I 1672 51.5 518 15.9 183 5.6 871 26.8 2 F-W-W I I 1686 44.8 1015 27.0 187 5.0 872 23.2 3 F-Flx-W I I 1666 42.3 993 25.2 407 10.3 866 22.0 4 F-Rye-W I I 1486 42.9 995 28.7 108 3.1 872 25.1 5 F-W-W I 0 1678 48.0 614 17.6 326 9.3 870 24.9 6 O(hay)-W-W I I 1802 29.4 2644, 43.1 808 13.2 869 14.2 7 Flx-W-W I I 1752 29.4 2426 40.7 902 15.1 871 14.6 8,9,10 Contin.W I I 1776 27.7 2878 44.9 876 13.6 877 13.7 11 F-W I I 1646 52.5 451 14.4 161 5.1 869 27.7 12 Contin.W 0 I 1738 40.5 776 18.1 898 20.9 874 20.4 tPercentages refer to the proportion of the total energy input. Energy requirements for fertilizers, particularly N fertilizer, increased by more than 5-fold as cropping became more intensive. This was a result of the higher rates of N fertilizer that were required for wheat grown on stubble as compared to wheat grown on fallow. It reflects the build-up of soil N that occurred on summerfallow areas (Campbell et al. 1983b). The application of recommended rates of Nand P fertilizers represented from 14 to 45% of the total energy input of the rotations. Herbicide use also increased as cropping became more intensive because of the greater need to control grassy weeds. Energy expendi-tures on herbicides constituted from 5 to 21% of the total energy requirements of the rotations. Energy useage associated with the capi-tal items was similar among the rotations, but accounted for the great-est share of the total energy input for the rotations that included summerfallow. - 188 -Energy Output Total energy output generally increased as the proportion of summerfallow in the rotation decreased because of the greater annual grain production per unit area (Table 5). The continuous wheat rotation with N and P fertilizers applied had the highest energy output, while the fallow-flax-wheat rotation had the lowest. Energy output for the fallow-wheat rotation ranked second lowest. Within the continuous-type rotations receiving N and P fertilizer, substituting oat hay or flax for wheat reduced energy output by about 30%. Similarly, within the 3-yr rotations receiving N and P fertilizer, substituting flax for wheat or fall rye reduced energy output by about 39%. These results follow from the relatively low yields of flax that were recorded in the experiment (Campbell et al. 1983b) and the low metabolizable energy content of flax and oat hay for human consumption. Failure to apply N fertilizer to the 3-yr and continuous wheat rotations decreased energy output by 6 and 12%, respectively. Similarly, failure to apply P fertilizer to the 3-yr rotation decreased energy output by 12%. The annual variability in energy output was highest for the more intensive crop rotations because of the greater yield variability. Net Energy Produced and Energy Efficiency Net energy produced (i.e., energy output minus energy input) was highest for the continuous wheat rotation with N and P fertilizers applied, and lowest for the 3-yr rotation that included flax (Table 5). Net energy produced for the traditional fallow-wheat rotation ranked fourth lowest. The 3-yr and cant inuous wheat rot at ions with N and P fertilizers applied produced 20 and 32% more net energy than the compar-able 2-yr wheat rotation, respectively. Net energy produced was in-creased by the application of P fertilizer, but was unchanged by the application of N fertilizer. Table 5. Energy output, net energy Rotation number 1 2 3 4 5 6 7 8,9,10 11 12 Rotation F-W-W F-W-W F-Flx-W F-Rye-W F-W-W O(hay)-W-W Flx-W-W Contin.W F-W Contin.W Fert. N p o I I I I I I I I o I I I I I I I I o I Meant energy output - - MJ/ha 13780cd 14633bc 8689e 14055cd 12867cd 12732cd 12856cd 18309a 12157d 16125b produced, and energy efficiency Std. dev. 4633 4695 3682 4987 4226 4650 4301 5717 3599 5595 Index¥ Net Energy t of mean energy output/ energy produced input output MJ/ha ratio 113 10531 4.24a 120 10868 3.89a 71 4752 2.21c 116 10590 4.06a 106 9375 3.68a 105 6602 2.08c 106 6898 2.16c 151 11896 2.85b 100 9025 3.88a 133 11833 3.76a TMeans followed by the same letter do not differ (p < .05) *The mean energy output for the fallow-wheat rotation was used as the index base (i.e., index= 100) - 189 -Energy efficiency of the rotations, as measured by the energy output/input ratio, ranged between 2.08 for the rotation that included oat hay and 4. 24 for the 3-yr wheat rotation that received only P fertilizer (Table 5). In contrast to net energy produced, the energy output/input ratios for the 2-yr and 3-yr wheat rotations with N and P fertilizer applied we.re higher than for the comparable continuous wheat rotation. The application of N and P fertilizer to the 3-yr wheat rotation did not significantly change the energy output/input ratios. For the continuous wheat rotation, the application of N and P fertilizer signficantly reduced the energy output/input ratio compared to when only P fertilizer was applied. This was due to the high energy requirement that is associated with the production of the N fertilizer input. CONCLUSIONS The results from the Swift Current long-term rotation experiment have shown that the input of non-renewable energy and the output of metabolizable energy for human consumption were directly related to the intensity of cropping. The traditional fallow-wheat rotation used by producers required the least input of non-renewable energy. This occurred because summerfallowing acts as a partial substitute for fertilizers and herbicides. A movement to more intensive crop rotations in the Brown soil zone will require the input of additional non-renewable energy and, under some circumstances, could require a doubling of the total energy input. Fertilizer, particularly nitrogen, will be the major energy input affected by a movement to more intensive cropping. Energy expenditures on herbicides will also increase because of the greater need to control grassy weeds. Energy expenditures on liquid fuels will not change greatly because the extra fuel required to plant and harvest the additional crop is largely offset by the fuel savings from reduced summerfallow tillage. Annual energy output for human consumption could be increased by as much as 51% by the adoption of more intensive crop rotations. The continuous wheat rotation with recommended rates of N and P fetilizers provides the greatest energy output. However, the energy output/ input ratio for this rotation is below that of comparable 2-yr and 3-yr rotations. This suggests that further research is needed to develop technologies that reduce the input of non-renewable energy (e.g., inclusion of legumes, green manuring, minimum tillage), improve the efficiency of energy use (e.g., improved fertilizer placement), and/or increase the energy output (e.g., snow trapping) of the more intensive cropping systems. REFERENCES BOERMA, H., M. GIMBY, and E. COXWORTH. 1980. A study of the energy consumption of different practices in Saskatchewan. Year III. Tech. Report No. 103, Sask. Research Council. - 190 -CAMPBELL, C.A., R. de JONG, and R.P. ZENTNER. 1984a. Effect of crop-ping, summerfallow and fertilizer nitrogen on nitrate-nitrogen lost by leaching on a Brown Chernozemic loam. Can. J. Soil Sci. (In Press). CAMPBELL, C.A., D.W.L. READ, V.O. BIEDERBECK and G.E. WINKLEMAN. 1983a. The first 12 years of a long-term crop rotation study in south-western Saskatchewan - Nitrate-N distribution in soil and N uptake by the plant. Can. J. Soil Sci. 63: 563-578. CAMPELL, C.A., D.W.L. READ, G.E. WINKLEMAN and D.W. McANDREW. 1984b. First 12 years of a long-term crop rotation study in southwestern Saskatchewan - bicarbonate-P distribution in soil and P uptake by the plant. Can. J. Soil Sci. (In Press). CAMPBELL, C.A., D.W.L. READ, R.P. ZENTNER, A.J. LEYSHON and W.S. FERGUSON. 1983b. First 12 years of a long-term crop rotation study in southwestern Saskatchewan - yield and quality of grain. Can. J. Plant Sci. 63: 91-108. JENSEN, N.E. 1977. Total energy budgets for selected farms in western Canada. Report to the Engineering Research Service, Agric. Can., Ottawa, Ont. LEACH, G. 1976. Energy and Food Production, IPC Science and Technology Press. NATIONAL ACADEMY OF SCIENCES. 1970. Nutrient Requirements of Beef Cattle (4th ed.). National Academy of Sciences, Wash., D.C. SOUTHWELL, P.M. and R.M. ROTHWELL. 1977. Analysis of output/input energy ratios of food production in Ontario. Report to the Engineering Research Service, Agric. Can., Ottawa, Ont. ZENTNER, R.P., P.V. BEAULIEAU, and W.J. BROWN. 1983. A documentation of the dryland crop enterprise model - version 1982. Mimeo., . Dept. of Agricultural Economics, Univ. of Sask., Saskatoon, Sask. ZENTNER, R.P., C.A. CAMPBELL, D.W.L. READ and C.H. ANDERSON. 1984. Economic considerations of crop rotations in southwestern Saskatchewan. Can. J. Agric. Econ. (In Press). 

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An energy evaluation of crop rotations in southwestern Saskatchewan

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