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The Citizen, 1989-11-22, Page 19PAGE 20. THE CITIZEN, WEDNESDAY, NOVEMBER 22, 1989. Be careful interpreting test plot information BY KEITH REID SOIL CONSERVATION ADVISOR WALKERTON O.M.A.F. This is the season we’re faced with an avalanche of plot results. The harvest is off, and every seed company, fertilizer dealer and chemical rep. is offering you irrefutable proof that their product or practice is the very best. Even . O.M.A.F. and the universities have been known to get into this game, with plot results of their own. The problem is, many of the results seem to be contradictory. How do you sort out the mess? Looking at plot results because they come in the mail can be interesting, but it is much more productive if we know what infor­ mation we are trying to extract. Let’s use the example of Peter Plowman, who wants to change his tillage system and is trying to decide what will suit his needs the best. Peter’s first step should be to throw out any data which he doesn’t know will be reliable. This includes plots which don’t include any supplementary information, or which don't include a check strip. He knows that plot results that he can't relate to his own farm are almost useless. He also knows that check treatments are necessary as a base for comparison, and to indicate how variable the field is. Spare use of buffers recommended by OMAF BY DENNIS MARTIN OMAF FARM MANAGEMENT SPECIALIST FOR HURON COUNTY Research has shown that the acid balance of the rumen can be artificially maintained using certain minerals. However, in nearly all situations, costs and feeding pro­ blems make long-term use of buffers less practical than ensuring that the ration provides enough “roughage effect’’ to support nor­ mal fat test. Consider buffers only under the following circumstances: 1. Herd butterfat test is continu­ ally depressed “relative to’’ the herd’s genetic potential even when all recommended feeding practices are followed. 2. Poor appetites are a problem with many high producing cows in the first two to three months of the lactation. 3. Silage-based rations where large amounts of grain are fed (i.e. greater than 13-14 kgs. grain per day). More of a concern if grain fed only two times per day. 4. Silage-based rations fed in combination with medium to high levels of ensiled grains (i.e. high- moisture corn, high-moisture bar­ ley). 5. When the grain mix being fed is fine-textured and is being offer­ ed in amounts exceeding 13 pounds per cow per feeding. This is a greater problem in silage and silage/chopped hay based rations than in rations where long hay is the primary forage being fed. 6. When the total dietary fibre level falls below the minimum levels of 17 per cent crude fibre (CF) or 21 per cent acid detergent fibre (ADF). 7. Just as important as fibre level the “effective fibre” content. /et, immature, finely-chopped irages are much less effective bre sources in promoting proper umen function and supporting fat est than long-stemmed dry hay. ;orages falling between these two ■xtremes support intermediate re- .ponses. 8. When the daily forage dry matter intake decreases to near 1.6 per cent of the cow’s average body weight. 9. When the proportion of the total dairy dry matter intake com­ posed of concentrates approaches the 50 to 60 per cent level. 10. In situations where rumen acidosis has been a frequently diagnosed problem. This step will eliminate plots which may have been useful, but it removes many more which are probably misleading. Peter’s next step is to look at plots grown on farms that are similar to his own. His farm is predominantly loam soils, so he knows that results from a sandy farm won’t apply to his own. The factors which should match fairly closely are soil type, drainage and management (fertilizer, planting dates, tillage, etc.) Peter doesn’t ignore the other plots; instead he uses them as a gauge of how consistent the treatments are that he is considering. He also looks at results from previous years to see if there are variations from one year to the next. The third step which Peter takes is to look at factors other than yield. He has found that reducing tillage on farms similar to his has shown a very small yield reduction compar­ ed to conventional tillage. He knows, however, that the savings in time, fuel, and equipment maintenance will be larger than any yield loss he might suffer. Peter’s other consideration is the state of his own equipment; his plow is nearly worn out, so his decision will be different than if he had just bought a new plow. Throughout this process, Peter has treated the plot results he sees with a healthy dose of skepticism. Most plots are planted to prove something, so Peter is always looking for any bias which may have been part of the plot design. He also tries to reason out any unexpected results, for example, was there a weed problem, or weather conditions, or herbicide damage? Growing crops is not always an exact science, because we cannot control ail the possible variables, but we can often explain what went wrong afterwards. This^xample dealt with someone assessing tillage alternatives. The same approach, however, will work with any plot results. It can be summarized in four points: •Throw out the garbage num­ bers, so you don’t waste your time looking at non-information. •Concentrate on plots with simi­ lar circumstances to your own, but check other plots for consistency. •Be aware of the factors besides yield. •Be skeptical. The only sure way to find out how something will work on your farm is to try it. Looking at plot results intelligently, however, will give you a good idea what to expect. 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