Prochaska, S.C., Extension Educator, Ohio State University Extension, Crawford County

ABSTRACT

Modified Relay Intercropping (MRI) is the planting of soybeans (Glycine max) into standing winter wheat (Triticum aestium L.). Fields are covered by growing crop about 13.5 months for each 14 month time period in this cropping system. Soybeans in the MRI system are sown into wheat with a grain drill or tool bar planter in late May or early June. The wheat has a tramline to facilitate soybean planting. The wheat plant, by virtue of its wide adaptability, is able to tolerate slightly wider row spacing and the stress of soybean planting with minimal yield loss. Ten years of replicated field trials on the MRI system have resulted in average plot yields of 74 and 30 bushels per acre for wheat and soybeans respectively. For wheat that was not interseeded, a 7 percent yield reduction for wheat grown in 15 inch rows versus wheat grown in 10 inch rows was observed over the 3 soft red winter wheat varieties and 5 years of study. When wheat was interseeded in 15 inch rows, there was a 7% decrease in yield from wheat not interseeded. A calculation of soil loss over MRI and other cropping systems found 1.9 tons per acre soil saved when MRI was used.

Introduction

While millions of dollars have been allocated to various conservation initiatives in Ohio and the Midwestern United States; there is evidence that many of the programs have failed to accomplish their objectives (Napier & Bridges, 2003). Further, although conservation tillage has been extensively promoted in many areas of the Great Lakes watershed, many farmers choose conventional tillage techniques (Great Lakes Regional Collaboration, 2006). As such, an alternative cropping system with environmental merit that might be adopted by farmers without economic penalty has been evaluated in Ohio (Prochaska, 2004). In the alternative cropping system, Modified Relay Intercropping (MRI) fields are covered by growing crop about 13.5 months for each 14 month time period.

Wheat is a flexible, adaptable plant with a growing season that starts with planting in the fall and ends with harvest in the early summer (Beuerlein, 2001). This adaptability allows farmers to capture some 66% of the traditional growing season in Ohio - May 25 to September 30 - to produce a second crop through the inter-planting of soybeans into wheat in late May or early June.

Long-term research at The Ohio State University's Ohio Agricultural Research and Development Center (OARDC), in Crawford County, Ohio and other locations in Indiana has shown that MRI or Relay intercropped wheat (used polymer coated soybeans) will yield about 90 percent of conventional wheat (Kline, McCoy, Vyn, West & Christmas, 2001), (Prochaska, 2003), and (Prochaska, 2001).

Because of the high probability of growing wheat in an MRI system at about 90% of conventional wheat, farmers may hedge their crop production and market risk in an MRI system through the opportunity (option) to grow and harvest a crop of soybeans (Prochaska, 2004). Soybean production in an MRI system is more speculative than wheat production due to the need for adequate rainfall in July and August (Kline, McCoy, Vyn, West & Christmas, 2001) and (Prochaska, 2004). Therefore, to study various MRI system production factors such as wheat row spacing effect on wheat yield, effect of intercropping on wheat yield and fungicide application to MRI wheat the following research questions directed the studies reported in this document. MRI studies examining other production factors have been conducted but are not reported in detail in this document due to word number constraints.

Research Questions

1. What is the effect of Proline fungicide on wheat yield in an MRI system?
2. What is the effect of intercropping on wheat yield?
3. What is the effect of row width on wheat yield?
4. What is the effect of USDA inoculated seed on soybean yield in a MRI system?

Methods

Methods differed depending upon the specific study objectives. Only those methods for the Proline question and row spacing study are reported in this document due to space constraints. A completely randomized design on a systematically tiled Blount soil was used to compare Proline fungicide treated MRI wheat to untreated MRI wheat over yield. Wheat (Agra 962) was planted on Oct. 6, 2007 at 1.38 million seeds per acre in 10 inch rows. Treatments were replicated eight times; however one replication was thrown out of the untreated plots due to severe wheel damage. Treatments (Control - untreated wheat and Proline @ 5.7 ounces per acre) were applied on May 24, 2007 at Feeke's wheat growth stage 10.5 with a calibrated sprayer delivering 12 gallons per acre. Wheat and soybean plots were 40 feet long and 60 inches wide and were harvested with a small plot combine on July 16, 2008. All wheat plots were interseeded with soybeans on June 12, 2008 with a Pioneer 92M91 soybean (205,000 seeds per acre). Soybeans were harvested Oct. 24, 2009 with a small plot combine. Wheat and soybeans were planted with a Great Plains drill set to 10 inch row spacing.

For the 5 year row spacing study, a completely randomized design with five replications in small plots (5.5 x 50 feet) was used. Treatments were 7.5 and 15 inch row wheat. Wheat was planted with a three-point hitch mounted tool bar planter harvested was done with a small plot combine.

Results

A reduction in wheat yield occurred to wheat grown in 15 inch rows over 5 years of study.

Table 1

Effect of Row Width on Wheat Yield
	7.5" Rows	15" Rows	F-Test	LSD (0.05)
Year and Variety	Bu/A	Bu/A		Bu/A
2000 I9824	72.3	70.8	<1	NS
2001 AGRA GR962	86.7	79.2	14.5	4.4
2002 AGRA GR962	85.1	76.8	28.3	3.5
2003 INW0301	66.8	58.6	19.8	4.3
2004 INW0301	86.5	84.7	0.9	NS
5-Year Average	79.5	74.0	.80	NS

Interseeding of wheat resulted in reduced yield compared to wheat not interseeded.

Table 2

Comparison of Wheat yields in a MRI and Conventional Production System, 1999 (bushels/acre)
Variety	MRI	Conventional
Hopewell	80	94
X15	80	93
Agra 962	88	95
Average	83	94
F value: 17.3	significant	LSD 7.6

Table 3

 

2000 Evaluation of USDA Soybean Inoculate on MRI soybeans
Treatments	Yield (bushels/acre)
Control	37.2
USDA Inoculate	37.1
F value .02, NS, CV=4.50

Table 4

Effect of Fungicide on MRI Wheat Yield in 2008 (bu/acre)
Treatment	Wheat Yield	MRI soybeans averaged 37.6 bushels per acre over all wheat plots.
Proline	86.4
Control	80.9
F-test 6.5, P = .025, Significant for wheat yield

MRI in a corn/soybean rotation will reduce soil loss.

Table 5

RUSLE2 Erosion Calculation Record*
Management	Contouring	Strips / barriers	Diversion/terrace, sediment basin	Cons. plan. soil loss, t/ac/yr
Corn FC Disk Fld Cult- Soybeans No Till Dbl Disk Openers - Wheat Disk 1X-NT DC Soybeans test	a. rows up- and-down hill	(none)	(none)	2.0
Corn FC Disk Fld Cult- Soybeans No Till Dbl Disk Openers test#2	a. rows up- and-down hill	(none)	(none)	3.2
Corn FC Disk Fld Cult- Soybeans No Till Dbl Disk Openers - Wheat NT- relay intercrop Soybeans	a. rows up- and-down hill	(none)	(none)	1.3

* Location Crawford County Ohio, Soil, Blount B, Slope 150 feet and 3.0%, T value is 4.0 tons/acre/year. Calculation done by NRCS personnel; Nathan Weber and Brad Van Voorhis

Summary

For wheat that was not interseeded, a 7 percent yield reduction for wheat grown in 15 inch rows versus wheat grown in 10 inch rows was observed over the 3 soft red winter wheat varieties and 5 years of study (Table 1). When wheat was interseeded in 15 inch rows, there was a 7% decrease in yield from wheat not interseeded (Table 2). The use of the USDA soybean inoculate on soybeans grown in an MRI system did not result in increased soybean yield (Table 4). Fungicides applied on MRI wheat at the correct time may result in increased yields when wheat disease is present or forecast to occur (Table 5). A calculation of soil loss in MRI (Table 5) utilizing the Revised Universal Soil Loss Equation 2 (RUSLE2) that compared corn, soybean and corn, soybean and MRI under various tillage alternatives found 1.9 tons per acre soil saved when MRI was used (Weber & Van Voorhis, 2009).

Conclusions

In the MRI system, wheat and soybeans have averaged 74 and 30 bushels per acre respectively in 10 years of replicated trials (summary includes trials reported in this document) on various production factors (Table 6).

Table 6

10 Year Average Yields in a MRI System (bushels/acre)
Year of Trial	Soft Red Wheat Yields	Soybean Yields
1994	65	41
1995	72	27
1997	70	28
1998	73	41
1999	83	5
2000	76	37
2003	67	29
2004	65	47
2007	84	0
2008	82	37
Grand Mean over all plots*	74	30

* This mean is of all plots conducted on factors of MRI

The alternate cropping system, MRI, is very favorable from an environmental perspective in that soil erosion is minimized and water quality preserved (Table 5). Yields in the MRI system have been at a level to make this system competitive in dollar returns to other crop rotations. Because two crops with vastly different growing seasons and cultural requirements are produced in the same field in the same year, MRI may offer both a production and marketing hedge.

References

Napier, T.L., & Bridges, T. (2003). Adaption of conservation production systems in two Ohio watersheds: A comparative study. Journal of Soil and Water Conservation 57(4): 229-235.

Great Lakes Regional Collaboration. (2006). Great Lakes Regional Colloboration Strategy to Restore and Protect the Great Lakes. Retrieved from www.glrc.us/.

Prochaska, S. C. (2004). Modified Relay Intercroppping. Fact Sheet AGF-504-04. Ohio State University Extension, The Ohio State University, Columbus, OH.

Beuerlein, J.E. (1990). Profitable wheat management. Bulletin 811. Agdex 112/10. Ohio State University Extension. The Ohio State University, Columbus, OH.

Beuerlein, J.E. (2001). Relay cropping wheat and soybeans. Fact Sheet AGF-106-01. Ohio State University Extension. The Ohio State University, Columbus, OH.

Kline, A., McCoy, S., Vyn, T., West, T., & Christmas, E. (2001). Management considerations for relay intercropping: I. Wheat. Agronomy Guide. AY-315. Purdue University Cooperative Extension Service, West Lafayette, IN.

McCoy, S., Vyn, T., Kline, A., West, T., & Christmas, E. (2001). Management considerations for relay intercropping: II. Soybean. Agronomy Guide. AY-316. Purdue University Cooperative Extension Service, West Lafayette, IN.

Weber, N., & Van Voorhis, B., (2009). Rusle2 worksheet erosion calculation record. National Resources Conservation Service. Bucyrus, OH.

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