A Comparison Of Soybean Seed Coat Technology In Relay-Intercrop And Double-Crop Production Systems.

Farmers are continually trying to increase grain yields and reduce production costs to increase farm profitability. Cropping systems in Northern Missouri shifted from including wheat in the rotation to primarily corn-soybean rotation due to a relatively strong corn and soybean prices. However, wheat is an important crop for soil conservation and building organic matter on highly erodible soils.

Double-crop soybean production is risky for farmers in Northern Missouri due to dry summers and risk of an early frost. Double-crop, no-till soybeans are often planted into dry soil in early July. These conditions commonly result in poor soybean growth and reduced stands. Timely summer rains are essential for high yielding double-crop soybean.

Relay-intercropped soybeans are planted into standing wheat. The growing season of the two crops overlaps in this production system. Previous research evaluated relayintercropped soybean planted in the southern United States (Porter and Khalilian 1995), Kansas (Duncan et al. 1990), and Nebraska (Moomaw and Powell 1990). Planting timing and mechanical injury to wheat reduced grain yields. Other research evaluated travel lanes in wheat; however, specialized field equipment and layout was required. However, none of this research included soybean seed coat technology planted into 15 in. wheat. Current soybean seed coat technology has included IntelliCoatTM and SuperKoteTM sources. These technologies may delay germination until conditions are suitable rapid soybean growth. Delayed germination would allow a farmer to plant earlier into standing wheat and reduce mechanical injury to the wheat. Seed coat technology could reduce risk associated with double-crop soybean and help farmers avoid a production disaster due to poor germination in dry soils or the risk of an early frost. Coated soybean seed may be provided at no additional cost to an additional $10/acre depending on the seed source. However, no independent evaluations have evaluated the performance and cost-effectiveness of different seed coat technologies in Missouri.

The use of seed coat technology is a production decision. Farmers can make simple modifications to equipment already owned to make relay-intercropping work; however, the cost-effectiveness and performance of the seed coat technology source in Missouri was unknown. Seed coat technology for soybean is a new concept and a comparison between technology sources was needed. The utilization of split-row (15 in.) planters for planting wheat and soybean in a relay-intercropping system may provide a cost-effective double-crop alternative and reduce risk associated with double-crop soybean in Northern Missouri. Therefore, the objective of this research was to evaluate soybean grain yield and the cost-effectiveness of seed coat technology used in a relay-intercropped production system compared with full-season and double-crop soybean.

This study was arranged as a split-plot design with four replications at the Greenley Research Center in 2003, 2004, and 2005. The main plot was cropping system (15 in. wheat followed by double-crop soybean, 7.5 in. wheat followed by double-crop soybean, 15 in. wheat with relay-intercropped soybean, and full-season soybean) and the sub-plots were soybean seed coat technology sources (Tables 1-3). Plot size was 10 by 40 ft. with four replications. ‘Pioneer 25R37’ were planted in 15 and 7.5 in. rows on 12 October 2002, 17 October 2003, and 8 November, 2004. Relay-intercrop and full-season soybean were planted on 23 April 2003, 28 April 2004, and 25 April 2005 at 200,000 seeds/acre. Plots were harvested with a small plot combine and moisture adjusted to 13% prior to analysis. All data were subjected to ANOVA and means separated using Fisher’s Protected LSD (p=0.05).

SuperKote soybean emergence was similar to non-coated soybean; however, germination was delayed 7 to 14 days with the Intellicoat seed coat technology (personal observation). This resulted in shorter soybeans that and approximately one vegetative stage behind non-coated soybean (data not presented). Wheat planted in 7.5 in. narrow rows had grain yields similar and up to 28 bu/acre greater than 15 in. wide-row wheat in 2003, 2004, and 2005 (Tables 1-3). Average wheat grain yield from 2003 to 2005 was 65 and 56 bu/acre in 7.5 and 15 in. rows, respectively.

Excessive early soybean growth may reduce wheat yields in a relay-intercrop production system. C4350 SuperKote in 2003 (Table 1) and all cultivars in 2004 reduced wheat grain yields except 5143 NRR Intellicoat soybean (Table 2) when compared to 15 in. wheat. However, no soybean cultivars reduced wheat grain yields in 2005 (Table 3). In general, relay-intercrop soybean grain yield was similar to double-crop yields in 2003. Relay-intercropped soybean grain yield was 19 to 58 bu/acre greater than double-crop soybeans in 2004 with coated soybean yields similar to non-coated soybean while wheat grain yields were greater with coated soybean compared to non-coated soybean. Soybean grain yields in 2005 will be determined.

Table 1. Wheat and soybean grain yield as affected by wheat row spacing, cropping system, and seed coat technology in 2003.

Table 2. Wheat and soybean grain yield as affected by wheat row spacing, cropping system, and seed coat technology in 2004.

Table 3. Wheat grain yield as affected by wheat row spacing, relay-intercrop system, and seed coat technology in 2005.

References:
Duncan, S.R., W.T. Schapaugh, Jr., and J.P. Shroyer. 1990. Relay intercropping soybeans into wheat in Kansas. 3:576-581.

Moomaw, R.S. and T.A. Powell. 1990. Multiple cropping systems in small grains in Northeast Nebraska. J. Prod. Agric. 3:569-576.

Porter, P.M. and A. Khalilian. 1995. Wheat response to row spacing in relay intercropping systems. Agron. J. 87:999-1003.

Wallace, S.U., T. Whitwell, J.H. Palmer, C.E. Hood, and S.A. Hull. 1992. Growth of relay intercropped soybean. Agron. J. 84:968-973.