I had a wonderful trip to the Grand Canyon over the Thanksgiving holiday. Unfortunately I came back to a smell house because my father-in-law, the dairyman, decided to put fresh dairy manure on the fields on the windward side of our house. Not only is this a nasty smelling mess it's also likely to generate a lot of weeds.
Most people are familiar with animal manures being very high in nitrogen, phosphorus, and potassium which are all required for plant growth. They are also high in organic matter which improves soil structure and water holding capacity. So one would think I should be perfectly happy that my father-in-law added dairy manure to our fields and they should be very productive next year. However, my experience over the past 23 years has been everywhere I put dairy manure in my garden I fight more weeds than produce vegetables or nice flowers. I've also heard my share of people in this community brag about the free dairy manure they spread on areas where they wanted lawn only to find out they got nothing but weeds. The problem with the manure is it wasn't properly composted before it was applied and that is exactly the case with the manure in the fields around my house.
Proper composting of animal manures requires piling it up in an area with a mixture of dry organic matter such as straw, autumn leaves, or other dead non-diseased plant residues. When mixed together and allowed to sit the bacteria in the piles works on breaking down the organic matter. During this process the pile gets very hot. Once this pile reaches a peak temperature in the center it should be stirred up to allow materials on the outside of the pile to also break down and cook. The heat from this decomposition process is hot enough to kill most weed seeds and insures that nutrients aren't tied up in the organic matter or bacteria once the compost is added to the soil. Also completely composted manure and organic matter has a much more pleasant odor.
If you don't have space for composting animal manure get it from a reputable garden center of dealer who has thoroughly composted the manure. Many communities don't allow composting or the application of fresh animal manure because it can leach into the local watershed causing environmental problems. In this case you will have to purchase your manure from a garden center which should only be getting it from sources that thoroughly compost it.
If you choose to compost manure yourself, check the Internet for proper ways to thoroughly compost it. There are lots of resources. Manure can be a good way to add organic matter soils in arid regions such as the Great Basin. These soils are typically low in organic matter. However, thoroughly composted manure can be a blessing but fresh manure can be a curse. My father-in-law cursed our whole property. Worse yet he's been doing so for years because that's the way his daddy did it and his son (my husband) will continue to do it. They don't readily listen to anyone who has a better idea. They claim the weeds can be taken care of by using 'Roundup Ready' seed but if you look at the photo at the top of this post you will see the results of 'Roundup Ready' corn. This field was treated with Roundup when the corn was a few inches tall. Between those rows of corn stubble and piles of manure are the residues of last season's weeds. Yes, the Roundup knocked back the weeds enough that the corn was able to out compete the weeds but no more Roundup was applied when the corn grew taller and made subsequent herbicide applications impossible. More weeds came up and even though they were shaded and somewhat stunted they still produced viable seed. The fresh manure in those piles will only add to the seed bank and some will blow onto my garden where I've stopped using animal manure. So I'll spend more time weeding than enjoying the fruits of my gardening.
