Current cropping practices in Iowa have reduced diversity in crop production to predominantly corn and soybean. Low prices, weed and pest control problems, and erosion have plagued these monoculture crop systems. Small grains and forages represent potentially viable alternative crops to corn and soybean in Iowa. Producers could opt for an annual intercrop that provides grain and forage without taking land out of corn and soybean for more than one year. This project tested the possibilities for combining small grains with a forage crop for a one-year intercrop

Brummer, Charlie W.

Holland, James

Current cropping practices in Iowa have reduced diversity in crop production to predominantly corn and soybean. Low prices, weed and pest control problems, and erosion have plagued these monoculture crop systems. Small grains and forages represent potentially viable alternative crops to corn and soybean in Iowa. Producers could opt for an annual intercrop that provides grain and forage without taking land out of corn and soybean for more than one year. This project tested the possibilities for combining small grains with a forage crop for a one-year intercrop.</p

Brummer, Charlie

Digital Repository @ Iowa State University (ISU)

98-68 COMPETITIVELeopold Center GRANT REPORT L E O P O L D C E N T E R FOR SUSTAINABLE AGRICULTURE Small grain and annual forage legume intercrops for Iowa Abstract: Current cropping practices in Iowa have reduced diversity in crop production to predominantly corn and soybean. Low prices, weed and pest control problems, and erosion have plagued these monoculture crop systems. Small grains and forages represent potentially viable alternative crops to corn and soybean in Iowa. Producers could opt for an annual intercrop that provides grain and forage without taking land out of corn and soybean for more than one year. This project tested the possibilities for combining small grains with a forage crop for a one-year intercrop. Background Breeding programs must account for variation in intercropping ability during the cultivar development program because breeding a spe­cies in isolation may not correctly foretell its performance when cultivated in an intercrop situation. Variety or species recommendations need to take into account the differences in performance under monoculture and intercrop growing systems. The interaction of cultivars or species in inter­crop systems can be evaluated in terms of general ecological combining ability (GECA) or specific ecological combining ability (SECA). GECA defines the performance of a species or cultivar over a range of companion crops. SECA refers to particular combinations of species or cultivars and indicates that inter­crop performance is dependent upon the spe­cific cultivars/species being tested. Statistical methodology is available to analyze these crop­ping mixture experiments. In prior work, the project investigators devel­oped three terms to clarify performance of a cultivar or species in an intercrop, defining it as general intercrop ability (GIA), which can be divided into general monoculture ability (GMA) and the general intercrop response (GIR). GIR represents cultivar differences observed in intercrops that are not accounted for by differences in monocultures. Thus, GIR differences among cultivars of the same spe­cies or functional group would indicate that intercropping performances cannot be pre­dicted from monoculture evaluations. These tools were used in the project for selection, evaluation, and variety recommendations. Project objectives were to determine the: •	 Potential agronomic values of several small-grain-annual forage legume inter­crops for Iowa farmers, and •	 Relative importance of GMA, GIA, and GIR effects among these small grain-an-nual forage intercrops. Approach and methods Five small grain cultivars (three oat with vary­ing maturity dates and two barley) and five forage species/cultivars, plus an alfalfa variety entered as a check crop, were included in the monocrop and binary intercrop experiments that were conducted at the ISU research farms near Ames (1997 and 1998) and Nashua (1997). Due to maturity differences among the culti­vars, an early group of entries and a late group of entries were defined and harvested at the appropriate time, roughly 7 to 10 days apart. Principal Investigator: Charlie Brummer Agronomy Iowa State University Co-investigator: James Holland USDA-ARS North Carolina State University Raleigh, NC Budget: $7,000 for year one $7,000 for year two Leopold Center Progress Reports	 Volume 10 (2001) All plots were harvested at least three times. Early forage plots in Ames (1997) were har­vested four times. Total forage yields were summarized over all harvest periods. Total crop biomass included all forage yields to­gether with small grain forage, grain, and/or straw where appropriate. Results and discussion Monoculture performance (GMA) Among small grains: The later maturing culti­vars were superior in total biomass under both management schemes. These cultivars pro­duced more cereal forage, grain, and straw than the early oat and the two barley cultivars. Among forages: Cherokee red clover, Mecca II alfalfa, and Bigbee berseem clover per­formed better than the annual medic species under both management systems. In addition to their higher yields, these forages also lim­ited weed yields to a greater extent. A major reason for the poor production from the med­ics was limited regrowth after the first cut. The early harvest treatment permitted some re­growth, but as a whole, their late season pro­duction was low. Berseem clover performance might have been understated, as its regrowth may have been depressed by the cutting height, which though standard for alfalfa and clover may be too low for berseem. The perennial, non-dormant cultivars proved most successful across environments. Intercrop performance (GIA effects) Among small grains: When grown in inter­crops, late-maturing small grain cultivars tended to have higher total biomass and to suppress forage legume yields more than the other cultivars. Later maturing grains had higher cereal legume, grain, and straw yields. Overall, when considering both early and late maturing cultivars, adding forage legumes to small grains increased total biomass, depressed weeds, and had no effect on grain, straw, or cereal forage yields. Among forages: Red clover, alfalfa, and to a lesser degree, berseem clover outperformed the annual medics in intercrops. The forages had little effect on grain or straw yields. Chero­kee red clover tended to have the least effect on oat component traits while simultaneously being least affected in terms of yield depres­sion by the oat companion crop. On average, adding small grains to forage legumes in­creased total biomass, but decreased the con­tribution of forage yield. Weed yields were reduced by the presence of small grains. Differences in performance between monoc­ulture and intercrop (GIR effects) Among small grains: Overall, few differences were seen among cultivars for GIR; that is, for the small grain cultivars tested here, differen­tial performance under intercrops and monoc­ulture was not evident. Among forages: Unlike small grains, GIR effects were pronounced among the forages tested. Much of the difference among species can be explained by Cherokee red clover. Total biomass increased substantially under intercropping with Cherokee red clover. Chero­kee yields were not reduced substantially by adding small grain in a grain management treatment, unlike all the other species, but its yield was reduced (though not as much as other species) under forage management. Significant small grain by forage legume SECA effects were noted for weeds under the forage harvest treatment and for biomass, legume forage, and straw under the grain harvest treat­ment. These results indicate that performance of particular grain-forage combinations can­not be predicted based on GIA. Leopold Center Progress Reports Volume 10 (2001) Conclusions Late-maturing oat cultivars produced more grain, straw, cereal forage, and total biomass than earlier-maturing cultivars of oat or bar­ley, but forage yields were decreased. Small grains tended to perform similarly under mo­noculture and intercropping; i.e., small or in­significant GIR effects were observed. Forage species differed markedly in terms of forage and biomass production. Perennial and nondormant cultivars of red clover and alfalfa, and berseem clover, were superior to two annual medics, mainly due to lack of appre­ciable regrowth of the latter. Cherokee red clover was both least affected by intercrop­ping and affected its companion crop the least. Weeds were suppressed by intercropping rela­tive to either small grain or forage monocul­tures. Impact of results Based on the results of this study, mixing Ogle oats with Cherokee red clover provides the highest yields and is least likely to perform poorly compared with all other cropping com­binations considered. The combination proved to be the most successful under both manage­ment systems—when small grains were har­vested for forage or for grain. Both the Mecca II alfalfa and Bigbee berseem clover also per­formed well in at least some experiments, and may represent viable alternatives. However, potato leafhopper feeding depressed alfalfa yields at some harvests, and berseem clover can perform very poorly in some environ­ments. The combination of forage and small grain resulted in nearly complete weed control and allowed successful forage establishment. Small grain companion crops should be rec­ommended for forage establishment. For more information contact Charles Brummer, Agronomy, Iowa State University, Ames, Iowa 50011; (515) 294-1415, e-mail brummer@iastate.edu Leopold Center Progress Reports Volume 10 (2001) 

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Small grain and annual forage legume intercrops for Iowa

https://dr.lib.iastate.edu/handle/20.500.12876/52966

Small grain and annual forage legume intercrops for Iowa

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