Strip Intercropping Corn and Alfalfa

Strip intercropping annual row crops can improve productivity, but the effect of strip cropping grain and perennial forage crops has not been thoroughly investigated. This study was conducted to evaluate the productivity and profitability of strip intercropping corn (Zea mays L.) and alfalfa (Medicago sativa L.). Alternating strips of corn and alfalfa of three widths (10, 20, and 40 ft) were compared in a field trial conducted from 1988 through 1990. Corn silking dates, heights, grain yields, and moisture were determined for each row within strips. Alfalfa yields and forage quality were determined for harvest strips within plots and for whole plots. Land equivalent ratios (LER) and gross returns to both strips and sole crops were calculated. In the drought of 1988, neither corn nor alfalfa yields differed due to strip width or from the sole crop yield. In 1989, corn yields were lowest for the sole crop (146 bu/acre), increased 3% in 40-ft strips, and 10% in 10- and 20-ft strips. In 1990, corn yields were also lowest for the sole crop (123 bu/acre), and increased 6% in 40-, 11% in 20-, and 17% in 10-ft wide strips. Alfalfa yields did not differ due to strip width or from the sole crop yield in 1989. In 1990, alfalfa yields in strips vs. the sole crop were reduced 10% only for the 10-ft wide plots. Land equivalent ratios were lowest in 1988, with values below 1.00 for 10- and 40-ft strips. All strip widths had values above 1.00 in subsequent years. Maximum LERs were 1.02, 1.08, and 1.06 for 20-ft strips in 1988, 1989, and 1990, respectively. In all years, 20-ft wide strips had the greatest economic advantage, returning $6, $29, and $17/acre over sole crops in 1988, 1989, and 1990, respectively. Increases in prices received for crops always increased the advantage of strip intercropping. Research QuestionStrip intercropping helps conserve soil and has the potential to increase economic returns from row cropping systems, but little is known in the USA about intercropping annual crops with perennial forage legumes. Objectives of this research were to determine the effects of strip intercropping corn and alfalfa on the growth and yield of each crop, on alfalfa forage quality, and to identify an economically optimum strip width. Literature SummaryStrip intercropping is the production of more than one crop in strips that are narrow enough for the crops to interact, yet wide enough to permit independent cultivation. Agronomically beneficial strip intercropping systems have usually included corn or sorghum, which readily respond to higher light intensities. Studies with corn and soybean strips four to 12 rows wide have demonstrated increased corn yields (+5 to +26%) and decreased soybean yields (−8.5 to −33%). Little has been documented in the USA about strip intercropping of annual species with perennials. Study DescriptionAlternating corn and alfalfa strips of three widths (10, 20, and 40 ft) were compared with sole cropping for crop yields and profitability in a field study from 1988 to 1990 in south central Wisconsin. Alfalfa was harvested three times in 1988 and four times in 1989 and 1990. Sole crop yield estimates were taken from the center four rows of corn and center alfalfa harvest strip of the 40-ft wide treatment. Corn growth and yield data were obtained for each row within treatments. Alfalfa yield and forage quality estimates were determined for alfalfa center and plot border harvest strips. Gross dollar returns per acre were calculated for each strip width. Applied QuestionsHow did corn and alfalfa yields compare for intercropping and sole cropping? Crop yield responses to strip intercropping varied depending on climatic conditions. In drought (1988), neither corn nor alfalfa yields differed due to strip width or from the sole crop yield (Fig. 1 and 2). In 1989, corn yields were lowest for the sole crop (146 bu/acre), increased 3% in 40-ft strips, and 10% in 10- and 20-ft strips (Fig 1). In 1990, corn yields were also lowest for the sole crop (123 bu/acre), and increased 6% in 40-ft, 11% in 20-ft, and 17% in 10-ft strips. Alfalfa yields did not differ due to strip width or from the sole crop yield in 1989 (Fig. 2). In 1990, alfalfa yields in strips vs. the sole crop were reduced 10% only for the 10-ft wide plots. Fig. 1Corn grain yields for 10-, 20-, and 40-ft wide strips (grown with alternating alfalfa strips of similar width) and the sole crop for 3 yr, 1988 to 1990. The vertical bar represents the LSD₀.₀₅ for strip widths within each year. Where no bar is shown, there were no differences among treatments. Fig. 2Alfalfa hay yields expressed at 12% H₂O for 10-, 20-, and 40-ft wide strips (grown with alternating corn strips of similar width) and the sole crop for 3 yr, 1988 to 1990. The vertical bar represents the LSD₀.₀₅ for strip widths in 1990. Where no bar is shown, there were no differences among treatments. Is this an economical practice? What strip width was most beneficial? In all years, 20-ft wide strips had the greatest economic advantage, with gross returns per acre over sole crops of $6 in 1988, $29 in 1989, and $18 in 1990 (Table 1). Increases in prices received for crops always increased the advantage of strip intercropping over crops grown in pure stands. Crop producers have to evaluate whether our observed range of $6 to $29/acre per yr additional returns for 20-ft wide strips would cover their labor and management costs to implement the new cropping system. More time and management may be required of farmers to implement a strip intercropping system. Tillage systems that allow controlled traffic and row placement (ridge till and no till) will probably maintain more uniform alfalfa strips than full-width tillage systems. Annual weed control in corn will probably include both chemical and mechanical means. Herbicide applications may be limited to banded granules or require spray shields for banding liquids. In addition, hay grown in strips may dry more slowly than that in an open field. In this study, forage was green chopped and mechanically dried. Table 1Gross returns per acre for sole crops and three widths of alternating corn and alfalfa strips for 3 yr, 1988 to 1990. Ship width, ftYear and cropSole crops102040--------------$/acre--------------1988 Corn†1027710296 Alfalfa‡122127128127 Total224204230223 Difference from sole crops--−20+6−11989 Corn172191188177 Alfalfa169169182184 Total341360370361 Difference from sole crops--+19+29+201990 Corn145170161154 Alfalfa209188212214 Total355358373368 Difference from sole crops--+3+18+133 yr average Corn140146150142 Alfalfa167161174175 Total307307324317 Difference from sole crops--0+17+10†Based on a corn price of $2.35/bu. ‡Based on an alfalfa hay price of $75/ton.