SHORT ON COMPOST? LET FINGERS DO THE WALKING.

Byline: JOSHUA SISKIN

``I'm getting all excited about spring and my vegetable garden. I need some organic compost in bulk, or any other organic, reasonably priced products that might work for me and my yard. I live in the foothills of La Crescenta, which has pulverized granite soil and rocks galore. I'm preparing a bed for organic vegetables about 50 feet long and 5 feet wide. The bed got all of the fallen leaves from my house and the neighbors' this past winter, but it needs more amending. My compost bin just doesn't generate enough for the whole yard. I would also like to top dress my St. Augustine lawn back to better health. It needs food and soil, maybe a sand and compost mix. What do you think?''

- Paula, La Crescenta

If you deposited heaps of leaves in your planned vegetable bed last fall, they will only be partially decomposed by now. Fallen leaves are rich in carbon but low in nitrogen. While any organic material, including leaves, will eventually break down, this breakdown will proceed much more rapidly in the presence of nitrogen. Mix in with your leaves a high- nitrogen organic fertilizer such as blood meal, hoof and horn meal or guano.

The best place to look for bulk compost is in the phone book under ``Soil Conditioners.'' You should pay $13 to $20 per cubic yard, plus delivery charges, for a general-use compost that sometimes goes by the name of ``commercial mix.'' This product may be used to prepare soil for planting lawns, gardens or vegetable beds. Purchased at the nursery in bags, a cubic yard of compost (27 cubic feet) would cost $35 to $65, so bulk ordering means considerable savings.

Some soil-conditioner suppliers may have a 10-cubic-yard minimum order. This quantity will be appropriate for amending 1,000 to 1,500 square feet of soil, depending on the thickness of the layer of compost that is spread before forking or tilling it into the ground. A 2- to 3-inch layer of compost is recommended when amending soil.

You raise the subject of top dressing, a procedure designed to fertilize and/or increase bacterial life in the soil, leading to improved soil drainage. This may be particularly important in compacted lawn areas. Where you have a compacted lawn, you can regularly top dress by spreading a thin layer, maybe one-half inch thick, of aged compost, such as Kellogg's Nitrohumus, over the area in question, once a month. Make sure you water in the compost as much as possible prior to the next mowing. Top dressing with a compost-and-sand mixture may also be effective in decompacting lawns.

Be aware that aeration of a lawn, which mechanically removes plugs of grass and soil, ought to be done immediately prior to top dressing to enhance penetration of the compost. Aerators are available at most equipment rental yards for $65 to $100 for one day's use.

``We are going to be doing some construction on our house in approximately two months and it will necessitate removing approximately 10 rose bushes, two camellia bushes (4 feet and 7 feet tall), three azaleas and a bunch of bulbs and irises. The bulbs and irises should be finished by that time so they could be dug up and replanted later, but I don't know what I can do, if anything, to save the roses, camellias and azaleas.''

- Deanne Piralov, Van Nuys

Your roses and azaleas should be easy enough to save. Dig up each plant with a spade, if possible, since its flat blade will preserve the integrity of the root ball (roots plus surrounding soil) whole. Assuming your azaleas and roses have reached maturity, you will need 15- to 20-gallon containers to accommodate their root balls. Azaleas and roses are easy to move.

Camellias are another story. You will have to exercise greater care in transplanting them. In the case of your 7-foot-tall camellia, you may need a 24-inch diameter clay pot or 24-inch-wide tree box to accommodate the root ball.