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a Dep. of Crops, Soil, and Environ. Sci., 115 Plant Sci. Bldg., Univ. of Arkansas, Fayetteville, AR 72701
b Dep. of Crops, Soil, and Environ. Sci., Univ. of Arkansas, Northeast Res. and Ext. Cent., P.O. Box 48, Keiser, AR 72351
* Corresponding author (lparsch{at}uark.edu)
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONINTERPRETIVE SUMMARYREFERENCES |
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Abbreviations: ACES, Arkansas Cooperative Extension Service • MSBG, Mississippi State Budget Generator • NR, net returns • TC, total costs • TFC, total fixed costs • TVC, total variable costs
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONINTERPRETIVE SUMMARYREFERENCES |
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For a cropping practice to be sustainable, it must also be profitable. One factor that contributes to the profitability of a conservation tillage system is that crop yield must compare favorably to that of a conventional system. Yield differences between conservation tillage and conventional tillage were examined by Hairston et al. (1990), who compared yield of soybean using no-till and conventional tillage on three Mississippi soils. Yields were similar between tillage systems on sandy soils for all 3 yr of the study. However, on silt loam and clayey soils, yield under conventional tillage exceeded no-till performance during most years. This yield reduction on finer textured soils was also noted in earlier studies by Hairston et al. (1984) and Dick et al. (1986a)(b) in Ohio. In North Carolina, Wagger and Denton (1989) found that no-till increased the yield of corn and soybean on sandy loam soils over conventional tillage over a 3-yr period. Similarly, in the north-central Texas Panhandle, no-till increased soil water storage during fallow periods, resulting in increased grain sorghum yields in a dryland system compared with conventional tillage and furrow diking in a limited-irrigation dryland system (Wiese et al., 1998).
Crop rotation is also employed to increase production in a conservation tillage system. In a Louisiana study on silt loam soils, Dabney et al. (1988) reported that soybean following either grain sorghum or fallow resulted in higher yield than continuous soybean. In Minnesota, Crookston et al. (1991) found that corn yield was 10% higher and soybean yield 8% higher in a corn–soybean rotation compared with these same crops grown in monoculture on a clay loam soil. In a 4-yr study by Edwards et al. (1988), yield of no-till soybean grown in rotation with corn on Alabama sandy loam soils showed an increase over continuous soybean that was conventionally tilled. In Ontario (Canada), an increase in rotational corn yield over continuously grown corn was reported by Raimbault and Vyn (1991) on silt loam soils. First-year corn in rotation showed yield increases ranging from 4% more than continuous corn under conventional tillage to 8% more than continuous corn under minimum tillage. In second-year corn, minimal response was attributed to rotation. At three sites in Minnesota and Wisconsin, Porter et al. (1997) reported a yield increase of 13% for corn and 10% for soybean when grown in annual rotations with each other over continuous monoculture. Furthermore, Wesley et al. (1994) and Singer and Cox (1998) reported greater net returns (NR) from crops such as corn and soybean grown in rotations.
The ability of a conservation tillage system to perform economically is critical to its acceptance by producers. An Illinois study of corn and soybean systems by Siemens and Oschwald (1978) found total production costs of eight conventional and conservation tillage systems to be similar. Although pesticide costs were higher for conservation systems, machinery costs were higher under conventional tillage. Jolly et al. (1983) compared economic returns and risk of four tillage systems in central Iowa for a corn–soybean rotation. Using returns to land and management as a measure of economic performance, they found that lower residue systems—such as moldboard and chisel plow—were preferred on a short-run basis (1–2 yr). However, on a longer term basis (3–4 yr), which allowed for reallocation of labor and capital, high-residue systems, such as strip-till and ridge-till, could become competitive. When comparing costs and returns for corn and soybean in Indiana, Doster et al. (1983) found that no-till, along with other conservation tillage systems, compared favorably with conventional systems on well-drained sandy soils. However, on poorly drained clayey soils, the conventional systems were more profitable than no-till. In an analysis of production costs for four tillage systems, including conventional and no-till, Klemme (1982) compared the per-bushel cost of producing soybean and corn in Wisconsin. The study concluded that if equal yields could be produced by each tillage system, then the cost of production on a per-bushel basis was similar and conservation tillage is competitive with conventional tillage.
In a more recent economic analysis of tillage systems, Liu and Duffy (1996) used producer survey data from the Iowa MAX (Farming for Maximum Efficiency) program to compare the profitability of conservation tillage with that of conventional tillage systems. They reported that most conservation tillage systems that included either no-till, reduced-till, ridge-till, or mulch-till had higher profits than conventional tillage with plowing. They also comment that conservation tillage systems can provide economic and environmental benefits.
In contrast to Liu and Duffy (1996), Johnson (1994)— in a review of literature pertaining to no-till soybean production practices—directed attention to several economic studies that found no-till had the lowest machinery and fuel costs and labor requirements. However, herbicide and other variable costs increased enough to offset the machine, fuel, and labor savings of no-till, resulting in no-till being less profitable than other tillage systems. Johnson also addressed concerns over weed control and pesticide loss in surface water runoff when using no-till.
These studies demonstrate that when yield is the sole measure of performance, no-till may perform favorably compared with conventionally tilled crops under certain soil textures and conditions. When making economic comparisons, no-till may also compare favorably with conventional tillage, with added benefits when crops are grown in rotation. Moreover, when both yield and profit are measures of performance, no-till may compare favorably with conventional tillage under coarse-textured sandy soils, but it has also been shown that no-till crop yields may compare less favorably on finer textured soils. Pesticide use and weed control are added concerns when utilizing no-till.
Limited published information is available on crop yields and economic returns of soybean, grain sorghum, corn, and cotton rotations for conservation tillage and conventional seedbed preparation on clayey soils. This information would be useful for producers in the Delta region of eastern Arkansas and throughout the Midsouth region of the United States where these crops are frequently grown on clayey soils. The soil management and conservation advantages of using conservation tillage, coupled with economic profitability, would make this farming practice both beneficial and desirable. The objective of this study was to compare yields and estimate the profitability of six cropping systems, each grown under conservation and conventional tillage on clayey soils.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONINTERPRETIVE SUMMARYREFERENCES |
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The field operations used in the study are typical for eastern Arkansas, with slight deviation from year to year and crop to crop due to variable conditions in soil moisture, weed pressure, and weather. All preplant fertilizer was broadcast as a solid material, and all sidedress was applied as 32% N liquid using a cutting coulter. Agricultural practices not specified were commensurate with those normally used by producers in this region. Field records were kept for each treatment including the date on which each field operation was performed, the quantity of operating inputs applied, crop and weather conditions, quantity and timing of irrigation, and yield. Common names and chemical formulations of herbicides used in the study are found in Table 2.
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Conventional Tillage Seedbed
Seedbed preparation for conventional tillage plots corresponded to typical practices in eastern Arkansas. These included a fall disking followed by either a spring disking or bed conditioning and a single cultivation after planting. For some producers, fall disking may be replaced by chisel plowing. However, moldboard plowing has disadvantages and was not used. Due to changing soil conditions or weed pressure, the number of tillage operations varied slightly from year to year and crop to crop for the conventional plots. Trifluralin (0.84 kg a.i. ha-1) and imazaquin (0.14 kg a.i. ha-1) were preplant-incorporated for soybean. On corn and grain sorghum plots, atrazine (2.24 kg a.i. ha-1) and metolachlor (1.68 kg a.i. ha-1) were applied pre-emerge. Metolachlor (2.24 kg a.i. ha-1) and fluometuron (2.24 kg a.i. ha-1) were applied to the cotton plots as pre-emergents. Raised beds for cotton were prepared using a stale seedbed system similar to those for conservation tillage cotton. In the conventional system, weeds are killed mechanically with a bed conditioner before planting cotton.
Soybean
‘Bedford’ was planted at a rate of 306280 seeds ha-1 during the 6-yr study on dates ranging from 11 May to 19 June. Row spacing was 0.97 m. Because soil test recommendations of the Arkansas Cooperative Extension Service (ACES) show no yield response to P and K on this soil, fertilizer was not applied to these plots. Soybean was harvested from the center of each plot on dates ranging from 7 October to 25 October, and the moisture level was adjusted to 13%.
Grain Sorghum
The cultivar Topaz was planted at a rate of 198000 seeds ha-1 on dates ranging from 18 April to 12 June. Row spacing was 0.97 m. Preplant fertilizer was broadcast at 84 and 56 kg ha-1 N and P, respectively, and 32% N liquid was sidedressed at 84 kg N ha-1. Grain sorghum was harvested from the center of each plot on dates ranging from 25 August to 22 October, and moisture level was adjusted to 14.5%.
Corn
‘McCurdy MSX 84’ was planted at a rate of 74100 seeds ha-1 on dates ranging from 18 April to 12 June. Row spacing was 0.97 m. Preplant fertilizer was broadcast at 112 and 56 kg ha-1 N and P, respectively, and 32% N liquid was sidedressed at 112 kg N ha-1. Corn was harvested from the center of each plot on dates ranging from 1 September to 5 October, and moisture level was adjusted to 14.5%.
Cotton
Before planting, a disk bedder was used to create raised beds in early winter. ‘Stoneville 506’ was planted at a rate of 135850 seeds ha-1 on dates ranging from 28 April to 12 June. Row spacing was 0.97 m. Preplant fertilizer was broadcast at 84 and 34 kg ha-1 N and P, respectively, and 32% N liquid was sidedressed at 84 kg N ha-1. First-picking cotton was harvested on dates ranging from 1 October to 26 October, followed by a second picking 10 to 14 d later.
Economic
To compare the profitability of the six systems under conservation tillage and conventional tillage, annual enterprise budgets were assembled based on field data collected over the 6-yr period of the study. An annual enterprise budget projects cost of production, gross revenue, and NR (Boehlje and Eidman, 1984) for a specified management alternative. All budgets were compiled with the Mississippi State Budget Generator (MSBG) using primary field data collected at the research site supplemented with estimates of prices and other technical coefficients where appropriate (Spurlock and Laughlin, 1987). Primary field data collected annually at the research site included (i) the treatment-level quantities of material inputs (fertilizer, seeds, chemicals, and irrigation) applied; (ii) treatment-level type, timing, and number of field operations performed; and (iii) replicate-level crop yield. Supplementary secondary data required for estimating cropping-system costs and returns included prices paid for inputs and materials, commodity prices received for crops produced, overhead and operating charges for machinery and irrigation equipment, and labor use. Because material input use and field operations were identical across plots, annual cost of production was estimated for each cropping system–tillage combination. By contrast, gross revenue and NR were computed for each replicate based on plot yield and commodity price received.
Input Costs and Output Prices
Annual enterprise budgets developed for each cropping system in the study employed input costs and output prices indexed to 1990 dollars and averaged over the period of the study. Prices paid for each of the material inputs used in the budgets (e.g., fertilizer, seeds, chemicals, and fuel) were taken from databases of 1986–1991 annual input prices maintained by ACES for preparing published crop enterprise budgets (ACES, 1986–1991). Each nominal input price was first indexed to 1990 dollars using the USDA index of prices paid by farmers (Agric. Stat. Board, 1992) and subsequently averaged over the 6-yr period. Correspondingly, crop output prices for commodities in the budgets were adapted from the 1986–1990 data series of prices received by Arkansas farmers (AASS, 1987–1991). Annual nominal prices for soybean, grain sorghum, cotton, and corn were first indexed to 1990 dollars using the index of prices received by Arkansas farmers (AASS, 1991) and then averaged. Indexed, averaged output prices used in computing gross revenue in the budgets were $0.229 kg-1 for soybean, $0.070 kg-1 for grain sorghum, $0.077 kg-1 for corn, and $1.208 kg-1 for cotton lint. Use of indexed, averaged prices for both inputs and outputs removes the effects of market volatility and inflation when estimating annual costs and returns over the study period.
Machinery and Irrigation Costs
Machinery operating (fuel, labor, repair, and maintenance) and overhead (depreciation and interest) costs were estimated using algorithms within MSBG and subsequently charged to each cropping system based on a representative eight-row machinery complement, which is commonly used in eastern Arkansas and included in crop budgets published by ACES (Windham et al., 1990). Equipment included 104 and 131 kW tractors, an eight-row combine for corn, 6.1-m grain head, two-row cotton picker, eight-row planter, 7.9-m disk, eight-row cultivator, 18.3-m high clearance sprayer, and a Do-All bed-conditioner with mounted sprayer boom. Machinery performance rates, annual hourly use, and lifetime hourly use of each machine were obtained from databases used in preparing ACES-published budgets (Windham et al., 1990). Custom charges were assessed for all fertilizer applications. Machinery labor use, fuel consumption, and machinery repair and maintenance charges were estimated within MSBG based on standards of the American Society of Agricultural Engineers (1987). Depreciation was computed for equipment using the straight line method, with prices reflecting replacement cost of the machinery complement in 1990 dollars. Finally, interest was charged at an annual rate of 11% on average capital invested (1990 replacement costs) in the machinery complement. Machinery operating and overhead costs were allocated to each crop budget based on the type and number of field operations performed for each cropping system.
Operating and overhead irrigation costs were determined in a manner similar to the cost estimates for machinery. All irrigation costs were estimated for a stationary 401-m center pivot sprinkler system, a system commonly used in Arkansas, which irrigates 52.6 ha. Irrigation labor use, fuel consumption, and equipment repair and maintenance charges were estimated per hectare-meter of irrigation water applied and then allocated to each budget based on the quantity of irrigation water applied to the field plots for each cropping system. Annual overhead costs (depreciation and interest on average investment) for the center pivot system were computed with irrigation parameters used by ACES in published cropping budgets and were charged against each cropping system at a constant rate per hectare.
Rotation Budgeting
Each enterprise budget for the study provided an estimate of gross revenue, cost of production, and NR on a per-hectare basis. Gross revenue and NR were computed at the replicate level based on commodity price and yield data for each plot. Two estimates of profitability were computed: (i) NR above total variable costs (TVC), which measures the contribution of each cropping system to annual farm overhead after direct, variable costs have been paid and (ii) NR above total cost (TC), which measures the contribution to farm overhead after all costs specified in each budget (direct and fixed) have been paid. The latter measure is more comprehensive and appropriate in the present study because differences in machinery complements across the cropping systems are properly accounted. Unpaid labor, overhead capital, land, and management charges were not cost-accounted in the budgets.
Because material input use and field operations were identical across replicates, annual cost of production was estimated at the treatment level for each crop–tillage combination. For the four continuous crops in the study (irrigated soybean, grain sorghum, cotton, and dryland soybean), each treatment-level crop budget reflects costs and returns for the corresponding monoculture system. However, for the two rotational cropping systems (soybean–grain sorghum and soybean–corn) in the study, NR and cost of production were computed for a rotated—i.e., a rotation-weighted—hectare. For rotations, treatment-level budgets for each of the two crops in a rotation were combined into a single rotation-weighted budget, which proportionately blends costs and returns from both crops in the rotation. A rotated hectare is composed of inputs and outputs in proportion to the amount of time that a given crop occupies the cropland relative to the amount of time for a cycle of the rotation. In essence, this proportion is a weight, which when multiplied by individual inputs and outputs, results in an annual enterprise budget containing proportionate costs and returns from each crop in the rotation. In principle, a hectare of land in a soybean–corn rotation, e.g., would consist of one-half hectare of soybean and one-half hectare of corn for each year of the rotation. The corresponding annual budget for this rotation would contain costs and returns from the summed production of one-half hectare each of soybean and corn.
Statistical Analysis
Statistical analysis using general linear modeling (SAS Inst., 1988) was performed to evaluate what factors affected yield and NR. All significant interactions are presented and discussed in the following sections. Significant differences for yield by year, cropping system, and tillage were determined using Fisher's F-test. Duncan's New Multiple Range Test and least significant differences (LSD) were used for mean comparisons of NR.
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RESULTS AND DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONINTERPRETIVE SUMMARYREFERENCES |
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The weather observed over the study period exhibited a range of conditions that can be characterized as normal for the humid southeastern USA. Short intermittent droughts during the growing season were frequently countered with wet periods during which the need to remove excess water was the main concern where drainage was a primary issue (Bruce et al., 1980). Average annual irrigation water applied across all crops during the study was 25.6 cm ha-1, which ranged from a low of 14 cm ha-1 (1989) to a high of 36 cm ha-1 (1988) annually. Average irrigation water applied by crop across years ranged between 23.6 and 29.3 cm ha-1 for grain sorghum and corn, respectively.
Variability in annual mean yields resulted in significant crop x year interactions for all five crops in the study (Table 3). Highest mean yield was attained in the same year (1987) for four (irrigated soybean, nonirrigated soybean, corn, and cotton) of the five crops. The relative range of yields observed over the 6-yr period was most dramatic for nonirrigated soybean, whose highest annual mean yield (1987) was more than four times its lowest mean in 1986. The crop with the lowest relative range of mean yields over the 6 yr was grain sorghum.
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Economic
Over the 6-yr study, all systems except continuous grain sorghum were profitable, as measured by NR above TC (Table 5). Cotton (CTI) and soybean monoculture (SBN and SBI) resulted in higher NR above TC than either of the 2-yr rotations (SBI–GSI and SBI–CRI), which contained soybean. Systems that contained grain sorghum—either in rotation (SBI–GSI) or monoculture (GSI)—ranked as the two least-profitable systems. The sole nonirrigated system in the study—monoculture soybean (SBN)—exhibited an average NR above TC that surpassed those of four other irrigated systems, including irrigated soybean.
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Seedbed preparation influenced the revenue and NR obtained from one growing season to the next (Fig. 1) . Conservation tillage resulted in higher gross revenue (Fig. 1A) in 1986, lower gross revenue in 1988 to 1990, and similar revenue in 1987 and 1991. Net returns above TC (Fig. 1B) showed that, except for 1986—a year whose midgrowing season was characterized by hot, droughty conditions—conventional seedbed preparation resulted in higher NR above TC than conservation tillage. Under severe drought, as occurred in 1986, conservation tillage showed improved performance over conventional. When the data were re-examined with 1986 removed, the tillage system x year interaction was nonsignificant, whereas the main effect of tillage system was significant (data not shown). The 5-yr mean of NR above TC for all non-1986 years was $188.64 vs. $138.19 ha-1 for conventional and conservation tillage, respectively, with an LSD (0.05) of $29.49. Thus, in 5 out of 6 yr, the conventional seedbed preparation was $50 ha-1 more profitable than conservation tillage.
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Because burndown chemicals were used only with conservation tillage seedbed preparation, the herbicide cost of all conservation tillage systems would be relatively less than their counterpart conventional systems if the study had been conducted with lower cost of burndown chemicals. Relative to conventional systems, the new lower prices of burndown chemicals would have reduced the cost of each conservation tillage system in Table 5 an average of $23.17 ha-1.
Nevertheless, even though lower burndown costs would have benefitted all conservation tillage systems by increasing their profitability relative to the conventional systems, the ranking of cropping systems by NR reported above would not have been affected. First, with the exception of cotton (CTI), conventional seedbed preparation for each of the five noncotton systems would result in higher NR than conservation tillage although the margins between the tillage systems in Table 6 would be narrower using the new lower burndown costs. Second, NR above TC for conservation tillage cotton (CTI) and monoculture conventional soybean (SBN and SBI) would continue to dominate the less profitable 2-yr rotations containing soybean (SBI–GSI and SBI–CRI), and monoculture grain sorghum (GSI) would continue to generate negative NR. Third, the TVC of conservation tillage production would still be higher than under conventional seedbed preparation for all systems with the exception of cotton, and TFC would be unaffected for all systems. Finally, with lower burndown costs, the only result that would alter the rankings previously reported is for TC of production. Across all systems, lower burndown costs would reduce TC of production for conservation tillage systems ($415.91 ha-1) in Table 5 to a level which, on average, is nearly identical to but slightly less than for conventional seedbed preparation ($416.04 ha-1).
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INTERPRETIVE SUMMARY |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONINTERPRETIVE SUMMARYREFERENCES |
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONINTERPRETIVE SUMMARYREFERENCES |
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