From eaclark@uoguelph.ca Fri Oct 29 14:48:45 1999 Date: Fri, 29 Oct 1999 11:08:37 -0500 From: E. Ann Clark To: "sanet-mg@ces.ncsu.edu" Subject: Re: no-till chemical use (long) Folks: mike (son of richard) richardson wrote regarding no-till: > However, it certainly can have tremendous environmental > benefits, compared to conventional farming (deep plowing, disking, > cultivating, etc.) Yes, generally more chemical amounts are used. > However, since the killed vegetation reduces soil erosion to near zero > (major benefit), absorbs chemicals, slows surface water movement, > reduces fertilizer loss, enhances water movement into the soil profile, > etc. then there is less chemical running off into surface waters. As > for chemical leaching into the ground water, that can be a problem with > some chemicals used in no-till and conventional tillage (atrizine types > for instance). However, many chemicals do break down while in the soil, > so as they are moving through the soil they tend to degrade. No-till > also enhances soil tilth, reduces fossile fuel use (thereby reducing air > pollution and global warming), lowers labor and equipment costs to the > farmer, and has been proven to maintain or even increase yields. Pasture - which is an "alternate" form of the livestock nutrition (grains) produced with no-till - does all of the above, and better - without need for chemicals in the first place. Let's not frame the discussion so narrowly as to create a strawman-type argument. If we really stand back and analyze land use practices objectively (whatever that is), starting with - what do we grow these crops for in the first place - this opens up a much wider array of options than just no-till or till. Might also add that even well managed no-till inherently and inescapably creates a whole suite of problems (which well managed pasture doesn't), including weed shifts to favor hard-to-control perennials like dandelion and quack. The obligatory dependence on herbicides (to the exclusion of all other approaches) also accelerates herbicide resistance (note Benbrook's authoritative commentary earlier on the increase in mean glyphosate use in the US in just the last few years, owing largely to no-till and RR crops (probably in that order too). In Ontario, long-time no-till farmers (experienced and commited people; leaders in the field) have begun to plow up their land, following several dry years in a row. For reasons that I still do not understand (given all the presumed increase in soil OM and water conservation under no-till (which is disputed, see below)), no-till land apparently has performed worse than tilled land under dry conditions. I'd have thought the reverse. It may have something to do with the accumulation of macropore space opening directly to the surface, conveying water too readily down to tiles before it can be absorbed. These same uninterrupted macropores, by the way, also convey liquid manure, herbicides, and anything else that has been surface applied directly down to tiles and out into surface water systems - completely bypassing buffer strips and other vehicles recommended to protect the integrity of watercourses. Colleagues in Land Resource Science tell me that no-till slows down the rate of loss of OM under annual arable cropping, but does NOT increase full-profile soil OM. Distribution is affected, with more concentrating in the surface layers, but less in the lower layers, with a net effect that total OM does NOT increase. The only way to materially increase soil OM is to withhold the land from cultivation under a perennial sod - like a pasture or hay field. And then there is the issue of N-use efficiency. I recall a paper co-authored by Rennie (former dean of ag at Sask and major proponent of conservation tillage) showing the potential for anaerobic microsites and anaerobiosis under surface vegetation on no-tilled land in the spring promoted denitrification and N-loss on wheat land. The amounts were fairly hefty if memory serves - say, 20-50 kg N/ha. Surface residues also keep soil colder longer, which effectively shortens the growing season in a short season climate, such as we have in Canada. Surface residues, particularly in combination with cold, can also retard plant establishment and seedling vigor, promoting susceptibility to a range of soil damping-off and other pathogens. Only certain crops *can* be grown no-till, which reduces rotation complexity and hampers the ability to constructively design rotations to deal with weed, pest, and nutrient management issues. Another unintended effect of no-till is leaving allelochemically active residues on the soil surface, where they can impact weed and subsequent crop growth. As it happens, one of the major no-till crops in Canada is no-till wheat. Research by Purvis et al., in Australia, has shown that the allelochemics released by decomposing wheat straw stimulate wild oat germination and growth. Thus, failure to incorporate the residues created a mega-problem with wild oats. And wild oats are a major problem in the prairies, which have adopted no-till wheat with a vengence. So, from a different (pro-pasture, admittedly) vantage point, no-till is a proprietary band-aid to patch up a arable crop technology (annual tillage to produce annual grain crops) that is fundamentally at odds with the ecological integrity of farm land. The problem(s) with tillage is soil erosion and degradation, with consequent effects on related processes, as water use efficiency. So, no-till addresses those issues, but in so doing, creates a suite of other issues. Pasture - which is what ruminants are actually evolved to eat in the first place - avoids most of these issues entirely (granted, you have to manage it to avoid overgrazing, erosion, etc.). Admittedly, pasture also creates some potential problems, relating to soil compaction (and water infiltration etc.) and N leaching/volatilization - although these are at least partly managable through such practices as restricting labile N (less chemical N; lower % legume). Management intensive grazing is a largely non-proprietary technology which can be mastered by men, women, and children, can be a useful (if not sole) source of nutrition year-around (even in Canada), and can retain a much larger share of farm gate receipts in the hands of farmers than no-till, conventional till, or any kind of annual arable cropping. Perhaps that is one of the reasons why commodity-specific subsidy/entitlement programs always favor annual crops and completely omit pasture (and often hay) crops. Ann To Unsubscribe: Email majordomo@ces.ncsu.edu with the command "unsubscribe sanet-mg". If you receive the digest format, use the command "unsubscribe sanet-mg-digest". To Subscribe to Digest: Email majordomo@ces.ncsu.edu with the command "subscribe sanet-mg-digest". All messages to sanet-mg are archived at: http://www.sare.org/san/htdocs/hypermail