From kandmhfarm@sprintmail.com Sun Jun 4 23:56:16 2000 Date: Sun, 4 Jun 00 22:45:30 -0500 From: kandmhfarm@sprintmail.com To: sanet-mg@cals.ncsu.edu Subject: Re: sanet-mg-digest V1 #1868 The question of at what scale herbicide use becomes necessary is a good one. We farm 1100 acres organically and we know that there are succesful organic farms that are much larger than ours. This is really more dependent on management than it is on scale. Done properly, organic weed control costs no more than chemicals do, if you figure the true cost of production . When you add to the comparison the large savings from not using insecticides and the avoided cost of chemical nitrogen, the economic justification for using chemicals also weakens. The use of chemicals becomes necessary especially if farmers don't use a good rotation and a balanced fertility program. The problem is that most farms are too specialized and don't grow a healthy mix of crops. The markets and government programs punish farmers if they don't put most of their acres into a very small number of crops (corn, soybeans, wheat). Livestock has all but disappeared from grain farms. At the same time, far removed from where they could actually be of benefit, nutrients from manure are polluting land around animal factories. Successful non-chemical weed control MUST be based first and foremost on cultural weed control. We have a long article in the June 2000 issue of Acres USA on the concept of cultural weed control, but we will summarize it here briefly. We strongly urge anyone interested to read further about this topic in Acres and comment/contribute their suggestions to us or to Sanet. Cultural weed control is defined as a combination of management practices that give the crop an advantage over the weeds. While chemicals often hurt both the weed and the crop, as well as the soil, cultural practices actually benefit the crop and soil, increase yield, and make any follow-up mechanical weed control methods much easier. This is especially critical if you had bad weather for optimal mechanical weed control. We are able to control weeds on our farm very well using relatively few trips over the fields - often only one pass with the row cultivator and 2 trips with a weeder (coil tine or Lely). It is critical that a farmer must not rely exclusively on mechnical weed control - that approach is either doomed to failure or can become extremely expensive. By using cultural practices, the farmer has a surprising amount of control over the weed populations and their vigor. It is exactly the lack of appropriate cultural weed control on conventional farms that has made weeds such a menace, requiring stronger and more expensive herbicides. It is therefore very important to note that cultural weed control should not just be viewed as 'an organic thing'. Any farmer, organic or not, can reduce their weed pressure and improve their crops by incorporating these ideas into their management. What does cultural weed control include? 1. Crop Competition Since a vigorously croping crop is less likely to be adversely affected by weed competition, any practice that promotes the health and vigor of the crop plants will reduce weed pressure. It is imperative to create conditions wehre the intended crop can establish dominance quickly. Using high quality seed, a well adjusted planter, well adapted varieties, optimal soil fertility, good soil drainage and tilth, and proper soil preparation will usually result in rapid vigorous crop growth. 2. Soil Fertility and Condition It is important to rely on the biological activity of the soil as the main source of fertility and of favorable soil physical structure. An active and diverse soil microbial population is the key to growing healthy high yielding organic crops. Successful organic fertility management should primarily feed the soil microbial life in a long term manner, rather than simply feeding the plants. Soil organic matter, especially material that is actively decomposing, is a tremendous source of plant nutrients and water holding capacity. Soil tests can be very useful, but only if the results are interpreted correctly. Careful attention to the calcium:magnesium ratio will often reduce weed problems and enhance crop plant growth. One common mistake made by many famers is the improper application of manure or poorly finished compost for soil fertility. When such materials are used, this tends to throw off the balance of certain soil nutrients and soil microbial life, and can actually increase weed growth. 3. Crop Rotation Civerse crop rotations that encompass the entire farm and that are planned a number of years in advance are essential to build a healthy sustainable organic system and to break pest cycles. In general, it is best to alternate legumes with grasses, spring planted crops with fall planted crops, row crops with close planted crops, and heavy feeders with light feeders. Careful use of cover crops when the ground would be bare adds organic matter, releases nutrients, improves soil microbial diversity and prevents erosion. 4. Allelopathy One way that crops compete with each other is by releasing chemical substances that inhibit the growth of other plants. Alleopathic crops include barley, rye, annual ryegrass, buckwehat, oats, sorghum, sudan-sorghum, wheat and sunflower. 5. Variety Selection Careful selection of crop varieties is essential to limit weeds and pathogen problems, and to satisfy market demands. Any crop variety that is able to quickly shade the soil between the rows and is able to grow more rapidly than the weeds will have an advantage. Disease resistant crops may also be of great advantage. 6. Sanitation The use of clean seed, mowing weeds around the edges of the fields or after harvest to prevent weeds from going to seed, and thoroughly composting manure to kill weed seeds can greatly reduce difficult weed populations. It is possible to hand eradicate small localized outbreaks of new weeds, even on a large farm. Other factors would include cleaning machinery used in weedy fields, and the establishment of hedgerows to limit wind blown seeds. 7. Deep shading crops By blocking sunlight from hitting the soil, a crop can effectively smother weed seedlings as they start to grow. Alfalfa, clover, and grasses are particularly good at shading, as are corn, sorghum and barley. Old German research showed that hemp was by far the best crop available for deep shading. Unfortunately growing this crop in the United States may attract 2 legged pests from the DEA. 8. Orientation of Rows Small grains have been shown to have less pressure if they are planted east-west, since that way the sun is not shining down the rows and the ground is more shaded. 9. Mismatching the lifecycle of the crop to the lifecycle of problem weeds For example, wild garlic comes up in the fall when you plant winter grains and matures at the same time - this makes garlic a particularly troublesome weed in these grains. Planting spring grains and row crops in fields infested with wild garlic or wild onion will reduce the problem significantly. Many of these practices are ones that good farmers probably do - or at least should do - regardless of whether they fully understand why they are doing them. As we gain a better understanding of cultural weed control, it becomes evident that many of the worst weed problems on conventional farms are actually the result of the farming system. Chemicals tend to facilitate poorer cultural practices on farms. Round Up Ready crops especially seem to make poor management practices possible, but that doesn't necessarily result in the highest quality or highest yielding crops. We try to see weed problems, especially specific localized ones, as a report on the condition of the soil and the lack of success of our management practices. Weeds can often teach us many things. For example, when we corrected a zinc deficiency on our farm, milkweed and hemp dogbane disappeared. If we see foxtail and other summer grasses coming in, this indicates a decline in soil tilth - usually around here due to too much magnesium. We've noticed that our quackgrass has virtually disappeared as our land was converted to organic management - isn't it ironic when we stopped using Round Up, our quackgrass went away? Hope this adds some perspective to the discussion. Klaas and Mary-Howell Martens (New York) To Unsubscribe: Email majordomo@cals.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@cals.ncsu.edu with the command "subscribe sanet-mg-digest". All messages to sanet-mg are archived at: http://www.sare.org/san/htdocs/hypermail