Hi Jim! Here's a few recommendations: 

1. What is the best way to deal with horse manure? What about composting in pits? Right now we have worm composting but it is only in the layers close to the ground. It makes nice compost but it does not treat the whole pile.

There are a few ways you can troubleshoot worm composting. One of them is to start building your compost piles in windrows, slowly and allowing for worms to colonize the whole pile before adding an extra layer. Depending on the size of the windrow, you may have to add a 3 inch layer of compost once a week or whenever you notice worms have moved uniformly through the pile. Worms prefer a moisture content of about 60-80% and temperatures of up to 90 degrees, although they prefer a range between 65-75 degrees. Your worms may be staying on the lower layer if the temperature or moisture on the top layers are changing as you add compost. You could possibly set up a few windrows of compost to allow for those temperature and moisture conditions to stay consistent. Using this method should also increase the amount of worms you have as they establish and reproduce, and they should eventually be able to treat or consume more manure. 

Using a pit would probably allow to make piles deeper and reach higher temperatures, which are great for decomposing organic matter and killing pathogens and weeds but you may not get to keep worms in fresh piles. There are pros and cons for both methods, so it will depend on your space and capability to manage the piles (worms will require adding a layer of manure maybe weekly, while pits may require you to turn the manure and monitor temperatures periodically).

Ultimately, on your current system, it sounds like the manure you add recently is not getting used by the worms but it is slowly aging and decomposing, which is still better than spreading fresh manure.

2. The manure we have spread over the years may be keeping what little moisture we have from getting to the grasses as it seems to create a thatch. (Even the weeds are doing poorly this year.)

You could drag or rake the fields to break down some of the compost from previous years. Using manure yearly in drylands is not always recommended. In dryland pastures organic matter takes a long time to decompose, which creates those thick layers of manure that may prevent moisture to reach the soils and block sunlight and air on the field. I would also recommend getting a soil and a manure/compost test done to make sure you are not over applying nutrients, this will also help you get a better idea of how much land you have available to use the manure, there’s a chance you may need to haul the manure out of the property. An option may be to rotate the spaces where you are applying the manure and only apply on one section every year.

3. Is aeration something we should consider? Our soil drains poorly and is hard and dry.

Research on aeration in pastures is a bit conflicting. It may help break down some of the organic matter on the top of the soil and initially help the existing grasses, however, no long-term benefits have been recorded when aerating grazing pastures. Hard and dry soils may just be natural characteristics of dryland pastures, and especially on clay type of soils, slower drainage is expected. However, if you notice areas where plants are not growing due to compaction, then these characteristics may be due to the constant traffic on the area, which can be changed by restricting grazing and encouraging grass growth. Having perennial plants on the soil is what will help drainage and infiltration easier on the soils, as the roots create spaces for air and water to flow naturally through the soils.

4. We have done chemical and pysical weed control. Broom Snake Weed seems to be the biggest problem but it does not seem to be doing well this year.

Repetitive mowing, especially after the plant has finished the vegetative growth stage (June-August) may be a good way to stress the plant, which will eventually kill it. Chemical control should be done while the plant is actively growing or in the fall when the plant is transporting nutrients to the root system. Expect to repeat both of these methods for at least a couple of years, especially in established mature plants.

5. We have a 10' deep gulley in our land which has not run for a few years now. We wonder what it would be like to dispose of animal manure in the gulley to fill it back to a normal level? Good idea or bad?

I do not recommend filling a gully with animal manure as it may be a source of contamination, especially If any sources of water are nearby. High quality composted manure can be used around a gully to prevent further erosion. Establishing vegetation around the gully to prevent further erosion is a more long-lasting solution.

I recommend this article with more detailed information to use composted manure to reduce gully erosion problems: https://extension.uga.edu/publications/detail.html?number=B1200&title=compost-utilization-for-erosion-control

I highly recommend you reach out to your local NRCS office (or CSU small acreage management depending on where you are located) to help you evaluate soil compaction and examine the possibility to remediate some of the gully erosion in the field. I think you can benefit a lot from an in-field evaluation.

You can reach out to me at <personal data hidden> and I can try to figure out who can do an in-field evaluation of the site. 

Best,

Karla Melgar Velis