Fruit & Vegetable Magazine

Features Production Research
Improving soil quality through management practices


November 30, 1999
By Dan Woolley

Topics

Management practices to improve soil productivity and quality present challenges for Atlantic vegetable growers according to the nutrient management chair at Nova Scotia Agricultural College.

Management practices to improve soil productivity and quality present challenges for Atlantic vegetable growers according to the nutrient management chair at Nova Scotia Agricultural College.


Dr. Mehdi Sharifi says low organic matter in regional soils is a big challenge for producers, as Maritime soils only have capacity to hold between five and 10 per cent organic matter. As a result, failure to fertilize or compost will mean low organic matter in the soil.

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Light, sandy soils have a low nutrient capacity and heavy precipitation on light textured soil leads to nutrient leaching, he says, adding that wet and windy conditions also lead to high nitrogen emissions from soil. This is particularly challenging considering there is no nitrogen test available for Maritime soils. (Dr. Sharifi is developing a soil nitrogen test for Atlantic Canada, which he hopes to release soon.)

Maritime soils also have low sulphur content due to minimal sulphur molecules in the rain, says Dr. Sharifi, adding many crops are sensitive to low sulphur content, particularly in cole crops and forages.
Low soil pH is also an important factor in soil health as it results in a nutrient imbalance in the soil, says Dr. Sharifi.

“Data indicates we don’t have enough lime to maintain pH,” he says, adding this results in an imbalance of nutrients.

A nutrient imbalance of phosphorus -– with high phosphorus in strawberry nurseries and low phosphorus in organic farms – can also affect productivity and nitrogen fixation in the soil, says Dr. Sharifi.

Weak soil structure and compacted hardpans are typically due to low organic matter plus too much tillage and equipment weight, says Dr. Sharifi. The soil conditions contribute to an abundance of weeds, pests and diseases, which need “more sustainable solutions than pumping more pesticide into the environment,” he says.

Despite these challenges, Dr. Sharifi sees many opportunities for producers to employ better management practices.

“We have access to manure and off-farm compost to biologically stimulate the soil and improve its nutrient contents,” he says.

Green manure cover crops also provide organic matter and nitrogen, biologically stimulate the soil, control weeds and reduce leaching, he adds.

Dr. Sharifi advocates using rotation between high nutrient demand crops and low nutrient demand crops, such as cereals to legumes to corn and potatoes.

He also recommends growers think about the timing and the method used when planning the application rates of their amendments. Increasing manure application rates on upland soils will increase the dry matter content of soils, he says.

“Beyond a certain point, there is a negative effect because there is an increased loss of nutrients to ground water.”

It will also take time to change the soils’ nutrient balance, says Dr. Sharifi. No-till has increased the proportion of nitrogen in test plots, with a significant increase in three out of four test plots, he says, adding there are definitely some benefits to no-till.

In rotation trials when no nitrogen is applied, Dr. Sharifi has noticed a significant improvement when peas and clover are added to the rotation and a significant difference with rye grass due to its high carbon content.

A five-year sustainable management trial to improve the soil is also currently underway at the Organic Agriculture Centre of Canada test site in Truro, N.S. Dr. Sharifi and fellow researchers are looking at how green manure should be used in the rotation and how much nitrogen to apply.

The team is working with four different rotations using green manure, red clover, oats, peas, vetch, carrots, potatoes and beans, with applications of composted municipal food waste and paper mill bio-solids.

They are looking at total tuber yields and total nitrogen uptake. So far, they have observed very little nitrogen uptake from paper mill bio-solids and a similar nitrogen uptake in tubers treated with municipal solid waste.

Dr. Sharifi said the total nitrogen uptake was greatest with fertilizer. Green manure with oats, peas and vetch in the rotations did not work as well at reducing carbon dioxide soil emissions as red clover did, he adds. During the winter, the soil did lose nitrogen. As a solution, the team planted a cover crop to capture and return the nitrogen to the soil over the fall and winter.

Dr. Sharifi is also testing mussel sediment as a soil amendment as he feels it will be useful on vineyards and orchards.

As well, he has tested soils in the Annapolis Valley for sulphur deficiency with 71 per cent of the test samples testing critical or below the critical level. Dr. Sharifi also plans to look at New Brunswick and P.E.I. soils.