From ACLARK@crop.uoguelph.ca Mon May 23 18:13:35 1994 Date: Sun, 22 May 1994 22:56:17 EDT From: "E. Ann Clark, Associate Professor" To: forage-mg@oes.orst.edu Subject: Query: re: complex mixtures and environmental heterogeneity A general enquiry to pasture researchers: I am working on a study regarding the role of mixture complexity in retarding weed encroachment on farm-scale pasture fields. In one 50 ac pasture sown to a 9-species mixtures in 1985 and grazed intensively (rotationally) ever since, only about 10% of sward biomass (on average) comes from weeds. This apparent resistance to weed encroachment is atypical of pastures in our area, and led to the hypothesis that mixture complexity could have been a factor in providing sufficient genetic variability to accomodate the range in environmental heterogeneity across the site. Subsequent measurements of species composition show that within a 1 m squared quadrat, the mixture has simplified down to about 3-4 species, but the particular blend of 3-4 species varies from place to place. This ongoing study has significant implications for testing protocol, because the advantage of a complex mixture (in sustaining sward longevity and retarding weed encroachment) may not be evident in a typical small plot clipping trial, which encompasses perhaps half an acre. I'd be interested to know if anyone else might be working on this area, and what you are finding. Ann ACLARK@crop.uoguelph.ca Fax: 519-763-8933 Phone: 519-824-4120 Ext. 2508 From RAYBURN@WVNVAXA.WVNET.EDU Mon May 23 18:14:30 1994 Date: Mon, 23 May 1994 16:00:47 -0400 (EDT) From: RAYBURN@WVNVAXA.WVNET.EDU To: forage-mg@oes.orst.edu Subject: complex mixtures Ann I agree with you even though I have little hard data to support me. However, being an ecologist by training the idea of mixes being more resistant to weed invasion than simple stands follows all we know about ecological systems. Across the northeast the best pasture I have seen in terms of quantity and quality have been pastures composed of mixtures usually a tall grass a short grass and white clover at a minimum (3-4 species as you said). Also my observation agrees with yours that simple stands often get more weed invasion than mixed stands. In my work in New York a farmer introduced me to the idea of planting ladino clover as a companion with alfalfa. Now anyone who has had a forage class has been taught that these don't "mix". They are complimentary. When I saw his alfalfa field I was impressed. The ladino clover was present only in the openings in the alfalfa canopy where weeds would have been if there was no clover planted. I have used this as a standard recommendation ever since. The term I use is that bluegrass in and orchardgrass clover pasture seeding or ladino clover in and alfalfa grass hay seeding are controlled "weeds". They are not really weeds, they are a planted species which gives more diversity of competition to potential weeds than using only the "desired" crop plants. They also have the potential of adding to yield by providing and under-story which captures light which goes through the main canopy. This of course goes back to forest ecology reduced in scale by a factor of 20 to 50. The old research at Cornell showing the advantage of planting birdsfoot trefoil with alfalfa on soils of mixed drainage and soil pH supports the principle. The trefoil was the major legume in parts of the field where drainage was poor or soil pH was lower. Ladino clover would fit into the same ecological niche as the trefoil but also has the advantage in that it can "run" across the field "looking" for the holes in the alfalfa stand or in a pasture. (Griffeth, WL R. Feuer, and RB Musgrave. 1965. Effect of soil pH and soil drainage on the yield and botanical composition of and alfalfa, birdsfoot trefoil and timothy mixture. Agron Dept. Cornell Univ. Agron. Mimeo 65-14.) I will be looking forward to your suplying us with more hard data. This is important area of work and fits in well with ICM (IPM) needs relative to weed control and insect control in alfalfa and pastures. Ed Rayburn Extension Forage Agronomist West Virginia University PO Box 6108 Morgantown WV 26506-6108 From SIMONS@mbrsbr.agr.ca Tue May 24 18:11:55 1994 Date: 24 May 1994 16:45:29 -0500 (EST) From: Richard Simons To: forage-mg@oes.orst.edu Subject: Complex mixtures Ann Clarke referred to using forage mixtures in which, if conditions are unsuited for one component or if there are gaps in the stand, another species can take advantage of the space, reducing weed ingress. This was part of the reasoning behind the Cockle Park mixture, widely used in Britain from the 1920s(?) into the 1950s. In a quick look, I have not found just when it was developed, but it contained perennial ryegrass, orchardgrass, timothy, red clover and white clover. I have just come across recommendations from the Netherlands in 1954. Mixtures for permanent pasture include : normal site wetter site perennial ryegrass (pasture type) 32% 29% perennial ryegrass (hay type) 16% 21% meadow fescue (pasture type) 7% 7% meadow fescue (hay type) 7% 7% timothy (pasture type) 7% 7% timothy (hay type) 6% 7% rough bluegrass 6% 7% Kentucky bluegrass 3% - white clover (pasture type) 3% 4% white clover (ley type) 13% 11% (Scheijgrond, W. and A. Sonneveld, 1954, Some factors influencing the behaviour of seed mixtures. Proc. European Grassld Conf., Paris, 21-24 June 1954. pp 178-184.) They do not mention why so many species were included, but do refer to changes in the sward composition depending on management, severity of winter, etc. Presumably the complexity is partly to ensure that, under all reasonable conditions, some desirable species would grow. It was probably also to achieve a reasonable balance of production during the year. I am curious as to how the recommended % compositions were arrived at. Richard Simons, Agric. Canada Res. Centre, Brandon, Manitoba SIMONS@MBRSBR.AGR.CA