Published in Agron. J. 96:1711-1718 (2004).
© American Society of Agronomy
677 S. Segoe Rd., Madison, WI 53711 USA
Production Papers
Early-Maturity Soybean in a Late-Maturity Environment
Economic Considerations
M. Poppa,*,
J. Edwardsc,
L. Purcellb and
P. Manninga
a Dep. of Agric. Econ. and Agribusiness, 217 Agriculture Bldg., Univ. of Arkansas, Fayetteville, AR 72701
b Dep. of Crop, Soil and Environ. Sci., 1366 W. Altheimer Dr., Univ. of Arkansas, Fayetteville, AR 72701
c Dep. of Plant and Soil Sci., 368 Agricultural Hall, Oklahoma State Univ., Stillwater, OK 74078
* Corresponding author (mpopp{at}uark.edu)
Received for publication December 22, 2003.
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ABSTRACT
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Over the last several years, farmers in the midsouthern USA have been planting earlier maturing soybean [Glycine max (L.) Merr.] cultivars. Maturity Group (MG) IV cultivars have become increasingly popular for reasons of drought avoidance and labor scheduling. Recently, research has been conducted to examine the agronomic characteristics and profitability of even earlier maturing cultivars. This study examines the economic considerations of MG 00 through MG IV soybean for two locations in Arkansas with different soil (silt loam vs. clayey soils) and weather conditions using both irrigated and nonirrigated production practices. Field trials were conducted over the period of 1999 to 2002. Net returns above direct and total expenses were calculated using cost of production estimates and experimental yields. Care was taken to isolate the impact of seasonal price effects as well as costs associated with irrigation, planting, and weed control as the remainder of production practices is similar across MG choice. Sensitivity analysis demonstrated that MG choice was driven mainly by yield differences and that seasonal price effects as well as changing seed cost, weed control practices, and irrigation costs had little impact. Producers may therefore choose to evaluate MG choice by following trends in yield potential. However, the analysis did not consider the farm-specific potential for labor cost savings that may occur due to changes in the timing of labor requirements. Further, the analysis does not explicitly consider seeding rate and glyphosate tolerance effects on MG choice.
Abbreviations: B/E, break-even • CDF, cumulative distribution function • EMG, early maturity group • MG, maturity group • NRAD, net returns above direct costs • NRAT, net returns above total specified costs
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INTRODUCTION
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MATURITY GROUP selection for soybean production in the midsouthern USA has typically focused on yield potential as well as suitability to local climate and soils, disease pressure, and water availability. While MG V, VI, and VII soybean cultivars are well adapted to this production region, late-season water availability and quality affect the ability to produce a successful crop due to drought stress, which typically commences mid-June (Purcell et al., 2003). Early soybean production systems, in contrast, complete seed fill before drought stress and allow for improved harvest weather conditions earlier in the year (Bowers, 1995; Heatherly, 1999). Maturity Group IV soybean has therefore experienced increasing popularity among producers (Hill et al., 2003). Early planting often does not occur until late April or early May (soil moisture and temperature conditions are unfavorable before those dates), which frequently results in exposure of MG IV cultivars to late-July and early-August drought. As a result, there continues to be interest in even earlier maturing cultivars (MG 00 to MG III) that are more common in northern regions of the USA.
Use of these early maturity group (EMG—MG 00 to III) cultivars compared with MG IV is expected to affect farmers in several ways. First, use of EMG cultivars changes production timing and therefore leads to different exposure to weather risk. On the positive side, this may lessen the impact of drought stress (Purcell et al., 2003) and advance the harvest to earlier in the season. Partial adoption of EMGs may also allow for labor cost savings due to rescheduling of field tasks (Casey et al., 1998). On the negative side, the shorter growing season may intensify risk by decreasing the amount of light intercepted. Second, use of EMG will affect marketing strategies by (i) often enabling the sale of new crop at old crop prices (see Fig. 1 for the potential impact of harvest week on price), (ii) government policy implications, and (iii) changing storage requirements. Third, production of EMG will require farmers to potentially use soybean cultivars that are not well adapted to the region, at least until EMG cultivars are developed for this region. Fourth, EMG production requires using higher plant populations and as a result may necessitate using conventional herbicide technology to avoid seeding costs of glyphosate [N-(phosphonomethyl)glycine]-tolerant cultivars. A final consideration is that EMG may reduce the amount of irrigation applied and/or avoid drought stress under nonirrigated conditions (Edwards et al., 2003).
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Fig. 1. Seasonality of Memphis, TN, cash soybean prices and study-relevant average weekly cash prices (1992–2003). Notes: Seasonal index values were calculated using a 52-wk centered moving average annual price. Price data were not adjusted for inflation and are available from the author upon request. The shaded area in the graph corresponds with the time period of harvest associated with maturity group across years in this study. Marketing and hauling charges are not deducted from the price series in this figure.
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Based on the findings of Edwards et al. (2003), this analysis focused on early planted soybean (April and May) ranging in maturity from 00 to IV for both irrigated and nonirrigated production at two locations with different soil profiles. Since the yield potential of EMG cultivars can be competitive with more traditional MG IV soybean under favorable conditions, central questions of this research were to determine the feasibility of EMGs on the basis of (i) seasonal cash sale price, (ii) irrigation requirements, and (iii) seed and attendant weed control costs. Economic thresholds under different resource conditions (soil conditions and input prices) were developed to provide producers with information to make seed selection decisions suited for production parameters they face.
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MATERIALS AND METHODS
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Data
Data from two different experiment trials were included in this study. All cultivars used were non–glyphosate tolerant and varied by location and year as summarized in Table 1. Experimental data were from short-season trials conducted in 1999, 2000, and 2001 at Fayetteville, AR (36°6'N, 94°70'W), on Pembroke silt loam (fine-silty, mixed, active, mesic Mollic Paleudalfs) and Keiser, AR (35°67'N, 90°3'W) on Convent silt loam (coarse-silty, mixed, superactive, nonacid, thermic Fluvaquentic Endoaquepts). Additional experimental data from a soybean density experiment were also available from Fayetteville and were used to add to the irrigated data from the short-season trials (2002 data for Fayetteville only). While experimental details pertaining to production methods can be found in Edwards et al. (2003), they are not included here as production practices, and inputs did not differ across MG with the exception of the amount of irrigation applied. Production cost differences (without irrigation) across MG would therefore not affect MG choice in this study.
To analyze the feasibility of EMG soybean production, the available data allowed analysis of (i) two soil conditions commonly found in the Midsouth, (ii) at least some weather and cultivar selection risk as experiments were performed over a number of years and several cultivars within each MG, and (iii) irrigated vs. nonirrigated production conditions. Data from Keiser were deemed representative of yield expectations on deep clayey soils with good water-holding capacity whereas data from the Fayetteville location were deemed representative of yield potential on shallow, silt-loam soils that require frequent irrigation due to poor water-holding capacity and shallow rooting depth of approximately 20 cm. Rainfall distribution and long-term weather patterns at both Fayetteville and Keiser are representative of the midsouthern USA (Purcell et al., 2003). This region is characterized by a low probability (<20%) of drought occurrence for the first 60 to 70 d of the cropping season followed by a high probability (>20%) of drought during mid-to-late summer. In general, these trends were observed for 1999 to 2002 cropping seasons at Fayetteville and Keiser (Edwards et al., 2003).
Methodology
Crop enterprise budgets were calculated for the activities conducted each year and on all plots using the Mississippi State Budget Generator (Laughlin and Spurlock, 2002) and input prices reported representative of Arkansas conditions in 2003 (Windham and Marshall, 2003). All MGs in the research plots were treated the same (except for irrigation) with minor differences in production practices across locations and years. These production practices included preplant tillage, fertilization, planting, weed control (not associated with seed cost), and harvesting. The direct or cash costs (fuel, herbicides, fertilizer, custom charges, hired labor, and repair) totaled $136.31 ha–1 at Fayetteville and $150.56 ha–1 at Keiser. Subtracting these costs from the per-hectare sales (yield in kg ha–1 x seasonally adjusted average price1 in $ kg–1) lead to short-run net returns above direct costs (NRAD in $ ha–1), which can be used to determine optimal MG (the MG choice with the highest NRAD for given location, year, and irrigation characteristics). Using a seasonally adjusted long-term average price (not adjusted for inflation) removes the impact of unusually high or low market prices but not the effect of seasonal price patterns.2
Long-run costs of equipment depreciation, insurance, capital repairs, taxes, and capital costs as well as land rent are expected to be similar across MG choice given similar equipment operations. Net returns above total specified costs (NRAT) were calculated by subtracting these long-run costs from NRAD. Average, positive NRAT are required to produce a crop in the long run, and NRAT data can be used to determine the likelihood of long-run break-even (B/E).
The cost of irrigation and seed/weed control costs were calculated subsequently for the purpose of conducting sensitivity analysis. As a baseline, irrigation costs of $2.92 ha-cm–1 were used to determine NRAD (Bryant et al., 2001). This irrigation cost estimate included fuel, irrigation labor, and repair costs for flood irrigation, which is the most common method of irrigating soybean grown in rotation with rice (Oryza sativa L.) in Arkansas. Past research has shown that the intrinsic value of irrigation may be as high as $20 ha-cm–1 (Popp et al., 2003). The intrinsic value or opportunity cost of irrigation are returns given up by using water on soybean instead of its next best alternative [i.e., irrigating corn (Zea mays L.) or rice instead of soybean]. Sensitivity analysis at higher irrigation cost estimates would thus favor use of MG with lesser irrigation requirements.
With the EMG cultivars there is a trade-off between seeding rate and yield. In these trials, the seeding rate was approximately 100 seed m–2. This seeding rate is expected to result in adequate canopy coverage and sufficient light interception so as to (i) reap full yield potential for the EMG cultivars (Ball et al., 2000; Purcell et al., 2002) and (ii) suppress weeds and therefore eliminate the need for an over-the-top herbicide application (Norsworthy and Oliver, 2002). Maturity Group III and IV cultivars, however, are predominantly grown using glyphosate-tolerant technology, and most producers choose a much lower seeding rate at the cost of at least one over-the-top herbicide application. Using 2003 prices, the cost of a lower-seeding-rate, glyphosate-tolerant system with one herbicide application was approximately the same as a high-seeding-rate, non-glyphosate-tolerant system with no postplant herbicide application. Therefore, the cost of the seed/herbicide program was priced at 2003 cost of $86.49 ha–1 for a baseline across all MGs. Note that producers choosing non-glyphosate-tolerant technology with EMGs need to manage the risk of glyphosate drift from neighboring fields. Sensitivity analysis across MGs is expected to reveal what kind of trade-offs between yield and seed/weed control costs exist (i.e., how much do seed/weed control costs have to change to compensate for yield differences). Note that the study did not specifically test for differences in seed and weed control costs, however, as no glyphosate-tolerant varieties were tested.
To be able to make MG recommendations, the different MG choices were analyzed by (i) comparing their empirical cumulative density functions of NRAD—each point on the cumulative distribution function (CDF) is an NRAD observation of a particular replicate in a MG for the years and cultivars available in the study (see Schlaifer, 1959, regarding particulars of empirical CDF construction); (ii) calculating the likelihood of profitability in the short (NRAD > $0) and long run (NRAD > $150 ha–1 for nonirrigated production and $300 ha–1 for irrigated production to cover land rent as well as fixed costs associated with equipment use)—likelihoods are estimated from the CDFs using linear interpolation between data points on the CDFs closest to the NRAD point analyzed; and (iii) conducting sensitivity analyses to establish under what conditions of soybean yield, seed/weed control, and irrigation cost MG choice would change from the "optimal" MG selection to the next best alternative.
The CDF analysis was performed to offer a visual examination of the observations across MG by location and production method (irrigated vs. nonirrigated). Note that only weather effects were truly stochastic whereas cultivar, spatial soil variation (replicates), and soybean price (linked to harvest date) were determined by experimental design. Note further that the data were not balanced across location nor MG within a location and production method (Table 1). Maturity Group III and IV tended to have fewer observations and a smaller number of cultivars (cultivar selection risk was lower for these MGs as they have been tested more for the region analyzed). The number of cultivars tested also varies by year for each MG as top-performing varieties were chosen from variety trials (Dombek et al., 2001). Using conventional CDF analysis techniques across MGs would thus lead to somewhat biased results.
For the sensitivity analysis, yields, applied irrigation, NRAD, and seasonal soybean price were averaged by MG while changing, one at a time, price or cost factors associated with MG choice. An example is solving for the B/E irrigation cost ($ ha-cm–1) that equates NRAD of the "optimal" MG choice with that of an alternative MG choice. Break-even is therefore the threshold at which a decision maker is indifferent between two choices. In this case, comparing two alternative MGs by dividing the difference in per-hectare sales by the difference in per-hectare irrigation provided the irrigation cost at which NRAD would be equal for the two alternatives. If one alternative resulted in lower yields at lower irrigation requirements, higher-than-current irrigation costs would be required to offset the yield disadvantage.
Statistical analyses were performed by location using the MIXED procedure of SAS (v. 8.2, SAS Inst., Inc., Cary, NC). Maturity group, year of production, and their interaction were treated as fixed effects, whereas cultivar, replication, and remaining interactions were considered random effects. Comparisons among MGs were performed using individual contrast statements at the p < 0.05 level of significance.
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RESULTS AND DISCUSSION
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Since analysis revealed statistically significant differences in NRAD by MG in most cases and always a significant year x MG interaction, the sensitivity analyses were presented by year and MG in Tables 2 to 4. Note that in nearly all cases, the optimal MG was the one associated with the highest yield and often with the highest seasonal price. An exception to the yield observation was the 2002 irrigated result at Fayetteville. This suggested that cost and seasonal price factors may not play a large role unless cost factors were to change from baseline conditions. Table 4 presents results using twice the current irrigation cost to show how the analysis would change if more emphasis was placed on differences in irrigation requirements.
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Table 2. Comparison of Maturity Group (MG) 00 to IV nonirrigated soybean production including sensitivity analysis on seed/weed control costs at Fayetteville and Keiser, AR.
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Table 4. Comparison of Maturity Group (MG) 00 to IV irrigated soybean production including sensitivity analysis on irrigation and seed/weed control costs at Fayetteville and Keiser, AR, using double the 2003 irrigation cost estimates.
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Table 3. Comparison of Maturity Group (MG) 00 to IV irrigated soybean production including sensitivity analysis on seed/weed control costs at Fayetteville and Keiser, AR, using 2003 irrigation cost estimates.
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Seasonal price changes were driven by differences in harvest dates. Harvest dates from earliest- to latest-maturing soybean cultivars differed by an average of 6 and 6.33 wk for irrigated production at Keiser and Fayetteville, respectively. For nonirrigated production, similar differences in harvest date were 6.5 and 7 wk at Keiser and Fayetteville, respectively. This resulted in average seasonal cash price effects (averaging by location and irrigation practice, the difference between maximum and minimum prices for a location and year) ranging from $0.008 kg–1 to $0.006 kg–1 regardless of irrigation at Keiser and Fayetteville, respectively. Also note that the highest prices did not necessarily coincide with the earliest MG. Even under irrigated conditions with high yields, this seasonal price effect was very small compared with MG differences in NRAD driven by yield. Seasonal changes in prices, therefore, will likely not affect MG choice. Being able to repay operating loans for production expenses at an earlier date with EMGs compared with later-season MG only had a minor impact as well (<$3 ha–1, data not shown). Given the focus on yield, the tables show the minimum yields that needed to be achieved for a producer to switch from the optimal MG. In most cases, these B/E yields were much higher than the average yields observed.
Tables 2 through 4 also suggest that required seed/weed control cost reductions did not affect the MG choice in any given year. For statistically significant comparisons between the alternative and optimal MG (see table columns entitled B/E Seed Cost Reduction and Statistical Significance), seed/weed control costs would have to be reduced by more than their original cost even under conditions where irrigation costs were doubled.
Finally, Table 4 presents economic thresholds when irrigation costs would alter optimal MG choice. Analyzing only the statistically significant observations in Table 4, the results indicated a minimum change from baseline irrigation costs ($2.92 ha–1) to $16.41 ha–1 (Fayetteville, 2001, MG 0—B/E Irrigation Cost). While this change in irrigation value was within the intrinsic value of irrigation of $20 ha-cm–1 range indicated above, it would not change the choice from an EMG to a more water-intensive production method listed here. Therefore, given the results of this analysis, should irrigation become less feasible due to cost, producers may be expected to switch to nonirrigated production rather than changing their MG choice.
In addition to the statistical and sensitivity analysis results presented above, CDFs of NRAD exhibit the range of results observed across years in Fig. 2. These CDFs thus provided a visual summary of the above results and added a risk analysis dimension (albeit with the limitations cited above). Maturity group CDFs furthest to the right were indicative of an MG that provided higher returns or lower chances of attaining poor NRAD outcomes. Steeper MG CDFs demonstrated a smaller range in outcomes and therefore lessened financial risk exposure.
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Fig. 2. Comparison of distribution of net returns above direct costs (NRAD) of (A and B) irrigated and (C and D) nonirrigated Maturity Group (MG) 00 to IV soybean at (A and C) Fayetteville and (B and D) Keiser, AR. Notes: Positive NRAD indicate ability to cover operating expenses in the short run. Vertical lines represent the threshold for positive net returns above total specified costs (NRAT) for irrigated and nonirrigated production systems.
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Visual analysis of the graphs indicated that MGs 00 and 0 were nearly always inferior to the remaining alternatives. Under irrigated conditions (A and B in Fig. 2), MGs I through IV exhibited very small likelihoods of short-run losses (NRAD < $0 ha–1). At Fayetteville (A), MG I and II CDFs were flatter until approx. $250 ha–1 than their MG III and IV counterparts, indicating lesser risk of not being able to recover fixed costs up to that per-hectare cost level. This made the EMGs preferable for a producer with a preference toward lesser financial risk. At Keiser (B), the more conventional MG III and IV soybean appeared to dominate the EMGs with the caveat that only 1 yr of observations are available. Under nonirrigated conditions at Fayetteville (C), MG I offered an alternative to the more risky MG III (note slope differences) and appeared to outperform MG IV. Under nonirrigated conditions at Keiser (D), MG IV was inferior to the EMGs, and MG III outperformed the remaining choices.
Analysis of the likelihood to produce a crop in the short run (NRAD > $0 ha–1) and long run (NRAT > $ 0 ha–1) demonstrated that EMGs were feasible alternatives under nonirrigated conditions and to a lesser extent under irrigated conditions (see Table 5 and y axis as well as vertical lines in Fig. 2). Interpretation of these statistics is very much a function of a decision maker's risk preferences, however.
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Table 5. Comparison of likelihood to earn positive returns in the short and long run for irrigated and nonirrigated Maturity Group (MG) 00 to IV soybean production at Fayetteville and Keiser, AR.
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CONCLUSIONS
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The results of this study indicate that MG choice analysis was primarily yield driven for the study conditions enumerated above. Early maturity group cultivars, therefore, may be evaluated on a yield basis since cost factors associated with MG choice were comparatively minor. Producers interested in EMG may determine optimal MG choice on the basis of yield potential at experimental locations without having to delve into economic considerations associated with seed/weed control costs, seasonal price changes, and/or irrigation costs as long as they face similar production conditions, soybean price, and input costs used in this analysis
Although a farming enterprise, producing a mix of MG choices rather than using a single MG, can realize labor cost savings due to improved labor scheduling (distribution of harvest over a wider window of time) (Casey et al., 1998), analysis of such labor savings is beyond the scope of this paper. Should a producer face a situation where their labor is over- or underutilized during the production season, changing seasonal labor requirements through MG choice should be entertained on a farm-specific basis. Finally, this analysis does not report on qualitative differences in soybean production across MGs (none were observed in this study), account for seeding rate or glyphosate tolerance differences across MGs, or consider the potential for additional crop enterprise(s) as a result of earlier harvest with EMG. These issues are left for further study.
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NOTES
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1 Using daily Memphis cash price observations from January 1992 to August 2003, a long-term weekly average price was calculated for each week in the year. In addition, a custom hauling charge of $0.0055 kg–1 was subtracted from the price to reflect current marketing charges and arrive at a net harvest price (USDA-AMS, 2003; Windham and Marshall, 2003). Price data are available from the authors on request. 
2 To determine the impact of inflation, the analysis was also performed by deflating the price data using the seasonally unadjusted Consumer Price Index (CPI) (USDL-BLS, 2004). Price levels would increase by approximately 15% regardless of harvest week if prices were adjusted for inflation to reflect prices in 2003 currency (the same year as the estimates of production cost). Choosing another index such as the producer prices received index is expected to lead to similar results. Rather than justifying the use of a particular index to account for inflation, the authors prefer to use the nominal price average as a reasonable and realistic expectation of long-term price for soybean as similar changes in price level across harvest week would not affect study results significantly in this study.
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REFERENCES
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ABSTRACT
INTRODUCTION
