Yield and Net Returns from Monocrop Winter Wheat Systems and a Winter Wheat‐Soybean Doublecrop System

Abstract

Economic evaluation of agronomic production practices is required to determine the feasibility of inputs used in cropping systems with two or more crops. The objectives of this study were to determine the effect of preplant tillage and seedbed type on subsequent monocrop wheat ( Triticum aestivum L.) seed yield and net returns, and compare the results with those from a wheat‐soybean [ Glycine max (L.) Merr.] doublecrop system (TRT 6). Net returns were calculated using data from plantings made for 4 yr on a Tunica clay (clayey over loamy, montmorillonitic, nonacid, thermic Vertic Haplaquept) near Stoneville, MS. Within the monocropped wheat treatments, preplant management inputs were: TRT 1—wheat planted flat following summer fallow; TRT 2—wheat planted flat following a summer legume crop [Hemp sesbania, Sesbunia exultutu (Raf.) Rydb. ex A.W. Hill]; TRT 3—wheat planted flat following summer fallow and subsoiling; TRT 4—wheat planted on 80‐in.‐wide beds following summer fallow; TRT 5—wheat planted on 80‐in.‐wide beds following summer fallow and subsoiling; and TRT 6—wheatsoybean doublecrop, where soybean was planted no‐till in burned wheat straw and wheat was planted in harrowed (disk and/or spring‐tooth) soybean stubble. Wheat yields from TRT 3 were among the highest each year, but net returns resulting from this treatment were among the highest in only 2 of the 4 yr. Combined net returns from TRT 6 were among the highest in all years, but they were positive in only 2 of the 4 yr and soybean yields averaged only 14.8 to 25.2 bu/acre. Net returns (losses in all 4 yr) resulting from TRT 2 were among the lowest each year because of the expense associated with establishing and incorporating the legume residue. These results indicate that monocropping of wheat, regardless of preplant management, is not a feasible replacement for winter wheat‐soybean doublecropping in a nonirrigated environ on clay soil, even though wheat yields were higher in the monocrop treatments in most years. Expenses associated with summer fallow maintenance for monocropped winter wheat were not offset by sufficiently higher yields. Research Question Doublecropping of winter wheat and nonirrigated soybean is a common and important practice in the southeastern USA. On the clay soils of the lower Mississippi River Valley, yield of soybean in this system is frequently low and results in little or no profit. Removing soybean from this system, or growing wheat as a monocrop, appears to be an alternative to wheat‐soybean doublecropping in this region. This study was conducted to assess the economic feasibility of growing wheat in monoculture vs. growing continuous doublecropped wheat and nonirrigated soybean. Literature Summary In the winter wheat‐soybean doublecrop system, soybean is planted no‐till in standing wheat stubble, following burning of wheat stubble, or in a prepared seedbed. Wheat is usually planted in a prepared seedbed following soybean harvest, even if the soybean crop is planted no‐till. Doublecropping wheat and soybean results in greater economic returns than those realized from a monocrop soybean system, especially when soybean is irrigated. No information is available on the effect of seedbed condition on yield and net returns from monocropped wheat, or on the economic feasibility of monocropping winter wheat. Study Description A field study was conducted from June 1991 through June 1994 on Tunica clay near Stoneville, MS. The study included six treatments: TRT 1—monocrop winter wheat planted flat following summer fallow; TRT 2—monocrop wheat planted flat following a summer legume crop of hemp sesbania; TRT 3—monocrop wheat planted flat following summer fallow and fall subsoiling; TRT 4—monocrop wheat planted on 80‐in.‐wide beds following summer fallow; TRT 5—monocrop wheat planted on 80‐in.‐wide beds following summer fallow and fall subsoiling; and TRT 6—wheat‐soybean doublecrop. Soybean (‘Pioneer 9592’) in TRT 6 was planted no‐till in 20‐in. rows, and all wheat (different cultivars in each year) was planted in 8‐in. rows in a prepared seedbed. Wheat stubble was burned in all years. Tillage using a disk harrow and spring tooth harrow was used to control weeds during the summer fallow months in the monocrop wheat treatments. Crop enterprise budgets were developed annually for each treatment. Application rates for all variable inputs were those used in this experiment. Variable expenses were the actual prices paid by farmers each year, and crop prices were the seasonal average prices received for each respective year. Total expenses included both variable and fixed expenses. Net returns were calculated annually as the difference between gross income and total specified expenses. Charges for land, management, and overhead were not included. Applied Questions Does yield of monocropped wheat exceed that of wheat grown in a doublecrop system with soybean and a summer legume cover crop? In 3 of the 4 yr of the study, yields from monocrop wheat treatments exceeded the yield of wheat grown in a doublecrop system with soybean (Table ). Wheat grown following a summer crop of hemp sesbania produced a yield that was among the lowest each year, and this yield never exceeded that from the doublecropped wheat. Does soil tillage treatment preceding wheat planting have an effect on wheat yield? Yield from wheat planted in the subsoiled and bedded treatment (TRT 5) never significantly exceeded that from the subsoiled flat‐planted treatment (TRT 3) or the bedded treatment (TRT 4) (Table ). Yield of wheat planted after subsoiling alone (TRT 3) was always in the highest yielding group and yield of wheat planted after bedding alone (TRT 4) was in the highest yielding group in 3 of 4 yr. Apparently, either subsoiling or bedding, but not both, offers the greatest potential for highest wheat yield on this clay soil. The 4‐yr mean yield from monocropped wheat planted flat with no subsoiling (TRT 1) was 7.5 bu/acre less than mean yield from monocropped wheat planted following subsoiling (TRT 3). Does monocropping of wheat result in increased net returns compared with wheat‐soybean doublecropping? Net returns from TRT 6 were the highest or among the highest in all years. Net returns (negative or losses in all cycles) from TRT 2 (monocropped wheat following summer legume) were the lowest or among the lowest in all years (Table ). Thus, the income from the soybean in TRT 6 was an important component of net returns from that treatment. Net returns from TRT 1 were among the highest in 3 yr, while net returns from TRT 3 and TRT 4 were among the highest in 2 yr. Net returns (losses in three of the four cycles) from TRT 5 were among the highest in only 1 yr. What is the overall assessment of a monocrop wheat vs. a doublecrop wheat‐soybean system? Growing only monoculture winter wheat, or the absence of a soybean crop between harvest and planting of winter wheat, did not result in increased net returns vs. those obtained from a continuous winter wheat‐soybean doublecrop system (Table ). Yields of wheat from the monocrop systems were sometimes greater than those from the doublecrop treatment, but net returns were never significantly higher. The inclusion of a nonirrigated soybean crop during the summer (15 June–15 Oct.) resulted in a yield of soybean that somewhat offset the costs incurred for weed control during this period. These results confirm the importance of using net returns as the criteria for selecting feasible or optimum cropping systems, especially when using different crops in the same system. Wheat yields and net returns above specified expenses‡ for monocrop wheat and doublecrop wheat‐soybean treatments (TRT) on a clay so near Stoneville, MS. Yield? Net returns TRT§ 1990–1991 1991–1992 1992–1993 1993–1994 Mean 1990–1991 1991–1992 1992–1993 1993–1994 Mean ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐bu/acre‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐/acre‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ TRT 1 9.1 bcd 35.2 b 50.0 bc 64.7 ab 39.8 −98.83 ab ∓14.19 a −8.44 bc 69.58 a −12.97 TRT 2 7.8 cd 22.3 c 48.4 c 39.8 c 29.6 −107.88 bc −69.45 b −20.04 c −10.72 c −52.02 TRT 3 9.9 abc 43.8 a 65.8 a 69.2 a 47.2 −112.12 c</ja

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