April 07, 2020

Achieving soil fertility> Green manure, cover crops can enhance gardens

With the gardening season more than just around the corner, many seasoned gardeners and novices too are delving into gardening literature for a horticultural fix, browsing magazine racks and bookstands, savoring lush-looking pictures of pretty gardens and sensational vegetables.

Winter reading seems to prompt questions of a thoughtful and scientific nature. My mail this month has indicated just that.

Here are two questions asked by readers on one of the most critical aspects of successful gardening: soil fertility.

Q. I was recently reading an article about organic gardening and would like to try some of the techniques. I think using green manures and cover crops is fascinating, but I just don’t know where to begin. Any suggestions? — T.W., Van Buren

A. Getting into green manures and cover crops can be as simple or complex as you’d like. Some definitions: Green manures are crops grown for turning under. Turning under the green leaves and stems of legumes and grains is a relatively inexpensive way to add valuable nutrients to garden soil.

Cover crops can be a range of crops grown to protect the soil resource in any season. Some gardeners use cover crops in the fall to protect against soil loss during the winter and spring months. Others use cover crops during the season in pathways and in rotation with certain crops.

Cover crops may double as green manures. For example, Dutch white clover used as a cover crop in garden paths may be tilled under once the garden is taken up in fall. When the clover is tilled under, the nitrogen-fixing legume acts as a valuable source of plant nutrients.

Popular green manures and cover crops include grains, such as oats, buckwheat and rye, and legumes, such as pea, hairy vetch and clover.

Single species of crops may be grown, or a mixture of several different species may be used to obtain a more complete nutrient source. For example, a good green manure mixture to sow in spring and early summer might contain two parts field peas, one part oats and one part vetch. This mix will thrive under the cool weather conditions of the early season. It should be sown at the rate of approximately 5 pounds per 1,000 square feet. You’ll soon recognize that its use will prove to be an excellent way to boost soil nitrogen level.

You can ease your way into using green manures and cover crops by simply sowing one onto your garden in fall or in spring before the crops are ready to be put in. As soon as you are able to work the garden soil in spring, a crop of peas, vetch or oats can be sown. After germination and any amount of growth, the crop may be tilled under and its benefits reaped.

Your system of green manuring and cover cropping may grow quite complex, once you’ve determined the ins and outs, the benefits and disadvantages, of different species. Until then, consider using a green manure-cover crop of oats in spring, buckwheat in summer and winter rye in fall on areas of your garden which are in rotation with garden crops. Use clover for path covers.

Q. As I think about gardening again this season, the daunting task of fertilizing the garden is making me consider downsizing my garden. I’ve always used manures and compost to get the job done, but that’s heavy and bulky work for this old-timer.

What are some of the advantages and disadvantages of using chemical fertilizers? — Y.M., Greenbush

A. Before you amend with any soil nutrients, you should be sure to take a soil sample and have it tested to get an accurate reading on what nutrients your soil requires. It is quite possible that your soil may be chock-full of nutrients if you’ve been applying manure at a regular rate for many years.

Chemical fertilizers do offer some convienience to the home gardener. Various chemical fertilizers may be used in liquid, granular, and slow-release forms. They are less bulky and less odoriferous than manure. Yet they still have their disadvantages.

Chemical fertilizers add no organic matter to the soil. Whereas manure adds lots of organic matter — an important ingredient in promoting long-term soil health — to the soil, chemical fertilizers are vacant in this department. Manures also add benefical microbes to the soil environment, again, an area where chemical fertilizers come up short.

Granular and liquid fertilizers are fast-acting, making nutrients readily available to plants. If placed too close to plants, granular fertilizers can burn plant tissues. This problem is somewhat remedied through the use of slow-release types. One disadvantage of slow-release fertilizers is that nutrient release is governed not by plant need, but by irrigation and rainfall.

As you see, as with any other aspect of garden management, various fertilizers have both pros and cons. Let your abilities and needs guide you in selecting your mechanisms for maintaining garden fertility.

Perhaps a combination of organic and inorganic fertilizers will accomplish the goal you are trying to achieve.

Diana George Chapin is the NEWS garden columnist. Send horticulture questions to Gardening Questions, c/o Maine Weekend, Bangor Daily News, P.O. Box 1329, Bangor 04402-1329. Selected questions will be answered in future columns. Include name, address and telephone number.

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