Pine needles are good for covering and cooling, but don’t achieve other goals
Mulch, as previously discussed, is a way to cover bare ground and hold down garden weeds, but these are only two of several uses. Mulch should cover the ground to (a) prevent soil erosion; (b) prevent or reduce weeds;
(c) keep the ground cool to allow increased vegetable production; (d) increase soil organic matter over time; (e) increase pore space in the soil and, (f) all the above. Ideally, you want a mulch that does all of these things. Unfortunately, mulches are often chosen that don’t come close doing all.
Pine needles for example, make excellent covering and cooling mulches, but have no effect regarding other goals. Pine bark also makes excellent covering and cooling mulch — but without grinding to almost a powder, doesn’t really improve soil. Shredded deciduous tree wood can eventually accomplish all the mulch goals, although it will take several years to improve the soil. If tilled in when the growing season is over, this begins improving soil organic matter (SOM) in the soil.
Increasing SOM is the most important long term goal, and the goal is to achieve 5 percent SOM. At 1 percent SOM, 100 pounds of dry soil can absorb less than 30 pounds of water. At 5 percent SOM, that same 100 pounds of soil can now absorb over 200 pounds of water.
Odds are, at 5 percent SOM, fertilizing may be unnecessary, with the organic matter now providing all of the necessary nutrients.
Weed control is important, but remember if the vegetable plant gets the water and nutrients it needs, it doesn’t care about weeds — which can also cover and cool the soil!
Now that we’ve had a frost and vegetable plants are dead/removed, put down a 4-6” covering of mulch. If you want to till it in, now is the time to do it.
Wall has a B.S. in Forestry from Oklahoma State University and an M.A. in Business Management from the University of Nebraska. He lectures throughout the area on gardening and is the vegetable gardening manager at Northeast Texas Community College.