Using organic matter in the garden

I have a large, perennial flower garden that requires 30 bags of mulch to cover it. Every couple of years I have to replace the mulch, and I wonder, where does it go?

Nina  Bassuk is an Urban Horticulture Institute professor at Cornell University. She says the mulch is lunch for fungi, bacteria, and other critters in the soil. These organisms help aerate the soil and break down complex nutrients into simple soluble forms that the plants can take up.

Bassuk says they did a 12-year study of adding organic matter in a perennial landscape.

"We add mulch every year until there’s enough biomass on top that’s dropping its own organic matter, and that process has actually improved the soil over the long-term. The day after we add the compost we improve the soil but 12-years of doing that and adding mulch to that initial input of compost actually had much better results than just the first year of doing that," says Bassuk.

Composted organic matter such as animal manure and kitchen scraps also improves soil density.

Bassuk says they’ve done a lot of work on soils that are degraded and compacted.

"In that case you need more compost to make an effect on heavier soils that have been compacted, at least 1/3-50%," she explains. "So 1/3 would be two scoops of soil to one scoop of compost, and 50% would be one-to-one by volume to make a difference in terms of reducing that density and reducing the compaction."

For a home garden, another way to determine how much organic matter you’ll need is to measure the overall planting area, and calculate how much compost it will take to cover the area with at least an inch.