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INTEGRATED SYSTEMS

Furrow and Flood Irrigation of Early-Planted, Early-Maturing Soybean Rotated with Rice

^a USDA-ARS, Crop Genetics and Prod. Res. Unit, P.O. Box 343, Stoneville, MS 38776 USA
^b Dep. of Agric. Econ., Mississippi State, MS 39762 USA

lheather{at}ag.gov

	ABSTRACT

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
The ESPS (Early Soybean Production System) is being adopted in the midsouthern USA to avoid some of the effects of normal late-season drought. Field studies with soybean [Glycine max (L.) Merr.] grown following rice (Oryza sativa L.) were conducted in 1994, 1995, and 1996 at Stoneville, MS, on Sharkey clay (very-fine, smectitic, thermic Chromic Epiaquert) to compare yield of Maturity Group (MG) IV and V cultivars grown under furrow vs. flood irrigation, and yield and economic performance of nonirrigated (NI) and furrow- and flood-irrigated MG IV and V cultivars. Three-year average yields from irrigated MG IV and V cultivars were significantly greater than average NI yield. Within each year, yields from MG V cultivars equaled or exceeded those from MG IV cultivars in all environments. Furrow-irrigated MG IV cultivars yielded significantly more than NI cultivars in all 3 yr, while flood-irrigated MG IV cultivars yielded more than NI cultivars in 2 of the 3 yr. Both furrow- and flood-irrigated MG V cultivars yielded significantly more than NI cultivars in 2 of the 3 yr. Three-year average net returns from furrow- and flood-irrigated environments were similar, and both were greater than those from the NI. Within each year, average net return from MG V cultivars in all environments was equal to or greater than that from MG IV cultivars. These results indicate that the ESPS can be used to effectively grow soybean in a rice–soybean rotation on clay soil, and that irrigation will usually result in greater profit from soybean.

Abbreviations: CSPS, Conventional Soybean Production System • ESPS, Early Soybean Production System • MG, maturity group • NI, nonirrigated

	INTRODUCTION

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
THE CONVENTIONAL SOYBEAN PRODUCTION SYSTEM (CSPS) in the midsouthern USA has involved planting MG V, VI, VII, and VIII cultivars in May and June, resulting in low yields during the 1970s and 1980s (Heatherly, 1999a). Crop water deficits in the midsouthern USA usually begin to develop in June and continue into September (Boykin et al., 1995). The subsequent drought that usually occurs in this region from mid-July through mid-September apparently is the prime cause for the low yields, since commonly grown MG V through VIII cultivars are in high-water-demanding reproductive stages during the same period (Heatherly, 1999b). Thus, they are most susceptible to the yield loss imposed by drought stress and concurrent high temperatures. A remedy for drought-related problems in the CSPS is to provide irrigation to overcome the water deficit during the severe drought periods (Heatherly, 1999b).

Land in the Mississippi River alluvial plain is flat, and a significant portion has been graded to facilitate surface drainage and furrow irrigation. However, the practice of grading or land forming remains expensive. A less costly alternative, contour flood irrigation, uses levees installed at the same elevation around and through relatively flat but ungraded fields. This method requires little or no grading of relatively flat fields. Straight levee irrigation uses levees that run perpendicular to the slope of a field to confine water to defined areas in fields that have been graded to slope in only one direction. This method requires moderate grading to ensure uniform field slopes. With either method, the levees separate field areas of different elevation, and water from rainfall and irrigation flows from the highest to the lowest point in each area enclosed by the levees. No matter what levee method is used, inundation of lower parts of a field will occur, resulting in submerged soil and standing water. Flood irrigation is used to irrigate soybean in the region (Heatherly, 1999b) because of its high efficiency, attributed to the dominance of crack filling during irrigation (Mitchell and van Genuchten, 1993). However, soybean cultivars differ both in their tolerance to flooding and in their ability to produce high yield under flooding stress (Heatherly and Pringle, 1991; VanToai et al., 1994).

In the 1988–1997 period, rice was grown on an average of 1.03 million ha in the states of Arkansas, Louisiana, Mississippi, Missouri, and Texas. A large portion of this rice acreage is rotated with soybean because of both crops' adaptability to the clay soils of the midsouthern USA. Kurtz et al. (1993) measured a 625 kg ha^-1 greater yield from MG VI soybean planted in May and June on Sharkey clay following rice and not irrigated vs. soybean following soybean, resulting in increased net returns of $141 ha^-1 ($20 vs. $161 ha^-1). Rice yields and net returns were also increased by rotation with soybean. Thus, a rice and soybean rotation system is preferred in the midsouthern USA.

Essentially all of the rice grown in the midsouthern USA is flood-irrigated (contour levee and straight levee methods). It stands to reason that soybean in rotation with rice will be flood-irrigated also, since the necessary facilities are already in place, and the costs associated with land forming necessary to facilitate furrow irrigation are high.

The ESPS concept (Heatherly, 1999a; Heatherly and Bowers, 1998) is being adopted in the midsouthern USA. Both indeterminate MG IV and determinate MG V cultivars are used in this system to avoid some of the detrimental effects of drought. Use of the ESPS concept for soybean grown in a 1:1 rotation with rice and its performance under flood vs. furrow irrigation have not been investigated. This field study was conducted to compare agronomic and economic performance of NI and furrow- and flood-irrigated (contour levee method) ESPS MG IV and V soybean cultivars when planted following rice.

	Materials and methods

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
Field studies with soybean were conducted in 1994, 1995, and 1996 on Sharkey clay following rice in a 1:1 rice:soybean rotation at the Delta Research and Extension Center, Stoneville, MS (33°26' N). All experiments were conducted using a randomized complete block design with four replicates in NI, furrow-irrigated, and flood-irrigated (contour levee method) environments. All production inputs within a year were identical for all cultivars and irrigation environments. Indeterminate MG IV and determinate MG V cultivars were used (Table 1) , and were changed during the 3 yr to reflect breeding progress and the subsequent release of new cultivars and unavailability of old cultivars. Seed were treated with metalaxyl [N-(2,6-dimethylphenyl)-N-(methoxyacetyl)-DL-alanine methyl ester] fungicide at 0.3 g a.i. kg^-1 of seed prior to seeding as a precaution against Pythium spp.

View this table: [in this window] [in a new window]   Table 1 Dates of reproductive stages (Fehr and Caviness, 1977) for Maturity Group (MG) IV and V soybean cultivars grown at Stoneville, MS, 1994–1996

A preemergent tank-mix application of metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5 (4H)-one] at 0.45 kg a.i. ha^-1 and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide] at 2.25 kg a.i. ha^-1 was made each year immediately after planting. In 1994, sethoxydim [2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one] at 0.21 kg a.i. ha^-1 was applied postemergence on 6 June to control annual grasses. In 1995, a postemergent application of premixed bentazon [3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] plus acifluorfen [5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid] at 0.84 kg a.i. ha^-1 was applied on 9 June to control broadleaf weeds. Postemergent herbicides were not required in 1996. Weather data in Table 2 were collected about 0.8 km from the experimental site by the Mid-South Agricultural Weather Service Center (National Oceanic and Atmospheric Administration) in 1994 and 1995, and by Delta Research and Extension Center personnel in 1996.

The field slope was 0.06%, and this allowed the entire flood-irrigated portion to be contained in one set of perimeter levees each year. The water source for the flood irrigation was placed in the upper end of the paddy. The incoming water entered the trench resulting from creation of outer levees parallel to the slope, traveled to the lower end of the paddy, and then filled the paddy from the lower end to the upper end. The paddy was considered flooded when the soil in the upper end was submerged. At this point, plants growing at the lower end of the paddy were in approximately 10 cm of standing water. The period from beginning of flooding to end of draining was 24 to 30 h at each watering. This time frame is within that shown to be appropriate for flood irrigation of soybean growing on this soil (Griffin et al., 1985; Heatherly and Pringle, 1991; Scott et al., 1989). To ensure that both depth of flood and time of flooding were maintained, drain pipes were placed in the top of the lower levees to allow for drainage of excess water during the flood period. Furrow irrigation was done by using gated pipe placed at the upper end of the field. Irrigation water traveled from the upper end to the lower end of the field through furrows spaced 2 m apart that were created by the tractor at planting. The aforementioned cracking allowed water to traverse the width between furrows so that all soil was saturated during the process.

Estimates of total costs (Table 3) and returns were developed for each annual cycle of each experimental unit. Total specified expenses (direct and fixed costs, excluding costs for land, management, and general farm overhead) were calculated using actual inputs for each treatment in each year of the experiment. Direct expenses included costs for herbicides, seed, labor, fuel, repair and maintenance, hauling, and interest on operating capital. Fixed expenses were annualized machinery ownership costs and annualized land forming costs. Costs of purchased variable inputs and machinery ownership were based on prices paid by Mississippi farmers each year. Cost estimates of all field operations were based on using 12-row equipment. Ownership costs for irrigation were computed for the engine, well, pump, gearhead, generator, fuel tank and lines, and mainline pipe. Direct costs were computed for the construction and destruction of the levees (flood irrigation) and the installation and removal of the polypipe (furrow irrigation). Fixed costs of machinery ownership and the irrigation system consisted of annual depreciation and interest on investment. Annual depreciation was calculated using the straight-line method with zero salvage value. Annual interest charges were based on one-half of the original investment times a nominal interest rate on borrowed capital. Irrigation fixed costs for the flood system were added to the NI budgets since virtually all rice fields have an irrigation system that would be used to irrigate soybean in a rice–soybean rotation scheme. Land forming for the furrow irrigation system was assumed to require the movement of 565 m³ of soil per ha, and was expected to last 25 yr with normal maintenance. An annualized cost for maintenance of graded land (equal to one-fourth of the initial furrow-irrigated land grading cost) was added to the furrow irrigation treatments because some maintenance would have been necessary each year. Within the NI and irrigated environments, expenses for all cultivars were essentially the same. The range shown in Table 3 is attributed to small differences in costs of planted seed and hauling of harvested seed (based on yield). Lower costs in 1996 were associated with less expenditures for weed control.

View this table: [in this window] [in a new window]   Table 3 Range in total specified expenses for Maturity Group IV and V soybean varieties grown following rice in nonirrigated and furrow- and flood-irrigated environments at Stoneville, MS, 1994–1996

Average height to tip of main stems was recorded for plants of each variety just prior to harvest, which occurred on 27 Sept. 1994, 12 and 25 Sept. 1995, and between 13 Sept. and 7 Oct. 1996. A field combine modified for small plots was used to harvest the four center rows of each plot. Harvested seed were weighed and adjusted to 130 g kg^-1 moisture content. Two 100-seed samples from each plot were used for determination of seed weight.

Analysis of variance (PROC MIXED [SAS Inst., 1996]) was used to evaluate the significance of effects on plant height, seed weight, seed yield, and net returns. Analyses across years treated year as a fixed effect to determine interactions involving year. Analyses for individual years treated MG as fixed and cultivar as random. To determine cultivar differences within year, both MG and cultivar were treated as fixed effects. Mean separation was achieved with an LSD_0.05.

	Results and discussion

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
Weather
Average maximum air temperatures in 1994 and 1996 were near normal for most months (Table 2). In those 2 yr, the months of June through August (reproductive period of all cultivars) had near or below normal moisture deficits (rainfall minus pan evaporation). Only 11 mm of rain fell in August 1994, but this was somewhat offset by the 294 mm that fell through 27 July. In 1995, average maximum air temperatures were 2°C or more above normal in April, May, and August. Moisture deficits in 1995 were above normal in May and August, but below normal in July. The 15 July to 31 August period of 1995 received only 66 mm of rain. Overall, each year of this study experienced periods of drought stress during some part of the growing season.

Reproductive Development
In 1994 (21 April planting date), R1 (beginning bloom) of MG IV cultivars occurred from 10 to 14 June, while R1 of MG V cultivars occurred from 17 to 20 June (Table 1). Full seed or R6 stage of the two MGs occurred from 22 to 29 August and from 26 August to 8 September, respectively. In 1995 (18 April planting date), DP 3478 and P 9501 reached R1 and R6 stages earlier than did MG IV cultivars in 1994, while R1 and R6 of RA 452 and HBK 49 occurred on dates similar to those in 1994. MG V cultivars reached R1 and R6 stages at about the same time as comparable cultivars in 1994. In 1996 (30 April planting date), a shift to earlier-maturing MG IV cultivars resulted in R1 and R6 occurring from 3 to 6 June and from 12 to 26 August, respectively. Maturity Group V cultivars started blooming on 21 June and reached R6 on 5 to 10 September.

Plant Height
Both furrow and flood irrigation significantly increased the average height of MG IV cultivars in 1994, but not in 1995 and 1996 (Table 4) . There was a trend in all years for average height of MG IV cultivars to be increased by both furrow and flood irrigation. Average height of MG V cultivars was not significantly affected by irrigation in any year. This disparate effect of irrigation on MG IV and V cultivars is related to the indeterminate growth habit of the MG IVs and the determinate growth habit of the MG Vs.

The premise at the beginning of the study was that short-statured cultivars might be more susceptible to an effect from soil submergence that occurs with flood irrigation vs. no submergence with furrow irrigation. Cultivar differences in plant height occurred within MGs of each irrigation environment each year (Table 4). These differences show the diversity in cultivars that were used in this study. By 1996, plant height of MG IV cultivars ranged from 60 to 90 cm, while height of MG V cultivars ranged from 49 to 92 cm. Hutcheson and A 5979, the two shortest cultivars in the study, were always among the highest-yielding cultivars regardless of irrigation environment (Table 5) , so short plant stature obviously was not a factor for yield in this study.

Seed Yield
Across the 3 yr of the study, the 3800 kg ha^-1 average yield from the furrow-irrigated environment and the 3610 kg ha^-1 average yield from the flood-irrigated environment were significantly greater than the NI average yield of 2860 kg ha^-1. Difference between 3-yr average yields from the furrow- and flood-irrigated environments was not significant. The NI soybean yields from this study, where soybean was rotated with rice, are greater than those from monocropped MG IV and V soybean cultivars that were planted on comparable dates at the same location on the same soil series, while the irrigated yields are similar (Heatherly, 1999a). Also, the average NI yield of 2860 kg ha^-1 measured from these April plantings of MG IV and V cultivars is 1030 kg ha^-1 greater than the average NI yield measured from MG VI soybean planted in May and June in a previous rice–soybean rotation study at this same location (Kurtz et al., 1993). Thus, use of the ESPS vs. the CSPS resulted in higher yields from NI soybean that was rotated with rice.

MG IV and V cultivars that were planted following rice and not irrigated produced average yields of 2595 and 3100 kg ha^-1 in 1994, 2550 and 2390 kg ha^-1 in 1995, and 2700 and 3835 kg ha^-1 in 1996, respectively (Table 5). Average yield from MG V cultivars was significantly greater than that from MG IV cultivars in 1994 and 1996, but not in 1995. In the furrow-irrigated environment, the 4020 kg ha^-1 average yield from MG V cultivars was significantly greater than the 3360 kg ha^-1 average yield from MG IV cultivars in 1994, but average yields from the two MGs were not significantly different in 1995 and 1996. Changing MG IV cultivars to those perceived as higher-yielding evidently contributed to the similarity in yields of the two MGs in 1995 and 1996. In the flood-irrigated environment, average yields from MG V cultivars were greater than average yields from MG IV cultivars in 1994 and 1996, but not in 1995.

Large and significant differences in yield among cultivars within a MG and irrigation environment occurred every year. This indicates that choice of cultivar is a major management decision in both nonirrigated and irrigated environments, and that changes to new and higher-yielding cultivars should be expedient. In 1994, yields of MG IV irrigated cultivars ranged from 3080 to 3705 kg ha^-1, whereas yields of MG V cultivars that were irrigated ranged from 3690 to 4300 kg ha^-1. In 1995, the ranges in yield for irrigated MG IV and V cultivars were 3370 to 4410 kg ha^-1 and 3010 to 4005 kg ha^-1, respectively, while in 1996 the respective ranges were 2420 to 4120 kg ha^-1 and 3400 to 4165 kg ha^-1.

Net Returns
Across the 3 yr of the study, average net return from the furrow-irrigated environment was $444 ha^-1, which was similar to the $435 ha^-1 from the flood-irrigated environment. Net return from both irrigation regimes was greater than the $322 ha^-1 average from the NI environment (Table 5).

Average net returns of $137 and $240 ha^-1 in 1994, $242 and $206 ha^-1 in 1995, and $402 and $703 ha^-1 in 1996 were produced from nonirrigated MG IV and V cultivars, respectively (Table 5). Average net returns from MG V cultivars in the NI environment were significantly greater than those from MG IV cultivars in 1994 and 1996, but not in 1995. In the furrow-irrigated environment, the $320 ha^-1 average net return from MG V cultivars was significantly greater than the $188 ha^-1 average from MG IV cultivars in 1994, but average net returns from the two MGs were not significantly different in 1995 and 1996 in the furrow-irrigated environment. In the flood-irrigated environment, average net returns from MG V cultivars were greater than average returns from MG IV cultivars in 1994 and 1996, but not in 1995.

Large and significant differences in net returns among cultivars within a MG and irrigation environment occurred every year. In 1996, net returns from Dixie (D) 478, DK 4875, and DP 3478 were especially low for the flood-irrigated vs. furrow-irrigated environments. This indicates that choice of cultivar is a major management decision for increasing profit as well as yield in both nonirrigated and irrigated environments. In 1994, net returns from MG IV irrigated cultivars ranged from $139 to $306 ha^-1, whereas net returns from MG V cultivars that were irrigated ranged from $256 to $403 ha^-1. In 1995, the ranges in net returns from irrigated MG IV and V cultivars were $351 to $643 ha^-1 and $285 to $556 ha^-1, respectively, while in 1996 the respective ranges were $266 to $687 ha^-1 and $498 to $699 kg ha^-1.

Both types of irrigation resulted in greater average net returns than did the NI treatment in 1994 and 1995, but not in 1996. Average increase in net returns from flood-irrigated MG IV and V soybean cultivars, respectively, was $103 and $117 ha^-1 in 1994, $278 and $249 ha^-1 in 1995, and $36 and $-102 ha^-1 in 1996. The respective average increase in net returns from furrow irrigation was $51 and $80 ha^-1 in 1994, $226 and $209 ha^-1 in 1995, and $236 and $-67 ha^-1 in 1996. As stated earlier, ownership costs of irrigation were included in the NI cost estimates because they are incurred even if irrigation is not used for soybean in a typical rice–soybean rotation.

	Conclusions

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 
April-planted MG V soybean cultivars grown in rotation with rice produced yields and net returns that were equal to or greater than those produced from April-planted MG IV cultivars in NI, furrow-irrigated, and flood-irrigated environments. Irrigation of MG IV and V cultivars that were planted following rice usually resulted in greater yield and net return compared with no irrigation. Properly timed and managed contour flood irrigation applied to MG IV and V soybean cultivars that were planted following rice usually resulted in yields and net returns that were comparable to those resulting from proper furrow irrigation. These results indicate that soybean rotated with rice should be irrigated for greater profit, that either furrow or flood irrigation methods can be used with generally equal results, and that MG IV and V cultivars can be used in the ESPS rotated with rice.SAS Institute 1996

	ACKNOWLEDGMENTS

 
The authors appreciate the expert technical assistance provided by Lawrence Ginn, Sandra Mosley, John Black, and Debbie Boykin, resources provided by the Delta Research and Extension Center, and supplemental funding provided by the United Soybean Board and the Mississippi Soybean Promotion Board.

Received for publication June 21, 1999.

	REFERENCES

TOP ABSTRACT INTRODUCTION Materials and methods Results and discussion Conclusions REFERENCES

 

• Boykin, D.L., R.R. Carle, C.D. Ranney, and R. Shanklin. 1995. Weather data summary for 1964–1993, Stoneville, MS. MAFES Tech. Bull. 201. Office of Agric. Communications, Miss. State University, Mississippi State, MS.
• Fehr, W.R., and C.E. Caviness. 1977. Stages of soybean development. Spec. Rep. 80. Iowa Agric. Home Econ. Exp. Stn., Iowa State Univ., Ames.
• Griffin J.L., Taylor R.W., Habetz R.J., Regan R.P. Response of solid-seeded soybeans to flood irrigation. I. Application timing. Agron. J. 1985;77:551-554.[Abstract/Free Full Text]
• Heatherly L.G. Response of soybean cultivars to irrigation of a clay soil. Agron. J. 1983;75:859-864.[Abstract/Free Full Text]
• Heatherly L.G. Yield and germinability of seed from irrigated and nonirrigated early- and late-planted MG IV and V soybean. Crop Sci. 1996;36:1000-1006.[Abstract/Free Full Text]
• Heatherly L.G. Early Soybean Production System (ESPS). In: Heatherly L.G., Hodges H.F., eds. Soybean production in the mid-south. Boca Raton, FL: CRC Press, 1999:103-118 a.
• Heatherly L.G. Soybean irrigation. In: Heatherly L.G., Hodges H.F., eds. Soybean production in the mid-south. Boca Raton, FL: CRC Press, 1999:119-142 b.
• Heatherly L.G. The stale seedbed planting system. In: Heatherly L.G., Hodges H.F., eds. Soybean production in the mid-south. Boca Raton, FL: CRC Press, 1999:93-102 c.
• Heatherly L.G., Bowers G. Early Soybean Production System handbook. St. Louis, MO: USB 6009-091998-11000. United Soybean Board, 1998.
• Heatherly L.G., Elmore C.D. Response of soybeans to planting in untilled, weedy seedbed on clay soil. Weed Sci. 1983;31:93-99.
• Heatherly L.G., Elmore C.D., Wesley R.A. Weed control for soybean planted in a stale or undisturbed seedbed on clay soil. Weed Technol. 1992;6:119-124.
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• Heatherly L.G., Spurlock S.R. Timing of furrow irrigation termination for determinate soybean on clay soil. Agron. J. 1993;85:1103-1108.[Abstract/Free Full Text]
• Kurtz, M.E., C.E. Snipes, J.E. Street, and F.T. Cooke, Jr. 1993. Soybean yield increases in Mississippi due to rotations with rice. Miss. Agric. & For. Exp. Stn. Bull. 994. Office of Agric. Communications, Miss. State University, Mississippi State, MS.
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This Article Abstract Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Heatherly, L. G. Articles by Spurlock, S. R. Search for Related Content PubMed Articles by Heatherly, L. G. Articles by Spurlock, S. R. Agricola Articles by Heatherly, L. G. Articles by Spurlock, S. R. Related Collections Soybean Economics Rice Crop Rotation Systems Agricultural Systems Crop Systems Irrigation