By Bruce Schundler

Both perlite and vermiculite have been used in the container industry for years. More recently, perlite has been used in both hydroponic growing systems and in 100% perlite applications.

What has been less publicized has been the use of fine vermiculite and perlite in field grown crops.

Brazil

In Brazil, for instance, testing was conducted in the 1980's to determine if vermiculite could help reduce seed mortality in field grown crops. When seeds are used to plant crops like carrots and tomatoes in soils that tended to dry out quickly, there has been very high seed mortality rates. To correct this condition, vermiculite was added to the soil to retain water and to improve the general soil conditions. It was also added in an attempt to retain nutrients through vermiculite's cation exchange capacity.

The test were conducted in areas where Brazil's soils were considered "oxy-soils" that have an extremely low rate of water and nutrient retention, and that represent 180 million hectares of land, 50 million of which are arable.

A Field of Caster Grown with Perlite (India)

Researchers determined quickly that large amounts of vermiculite would be desirable, but very uneconomical; and so they turned to using very small amounts of vermiculite with each plant. A small amount of vermiculite was concentrated at the bottom of the furrows, and applied at a rate of only 1 cubic meter per hectare which equals approximately 1 dL per lineal meter of furrow (or as little as 0.10 cup for every 39 inches or 0.00353 cubic feet for every 39 inches.)

Although minute in quantity, it was "noticed that plots where this technique was applied remained damp longer than neighboring plots where no vermiculite was applied," especially during dry spells.

This phenomenon is not yet fully explained, and experiements have been started to verify some very interesting theories that have been presented. If confirmed, it would indicate that vermiculite has a synergistic effect on some soils, resulting in a compounded water retention much larger than what would be expected from the small quantities of vermiculited applied.

"On the other hand, application of vermiculite at the bottom of furrows below the level of fertilizers will reduce leaching when heavy precipitations occur (150 mm in a single day), and, therefore, reduce the loss of fertilizer." This results in a higher efficiency in the use of both irrigation waters and fertilizers.

This new technology has already shown some very striking results. For example, in the 1988/1989 crop year, in a farm in the state of Minas Gerais, a 56% increase in yield was obtained in soybean drops, 15% in corn, and 13% in coffee.

Another interesting example: At Fazenda Rio Bonito, in the north-eastern dry state of Rio Grande do Norte, where rainfall is scarce and concentrated in a very short period, sorghum was planed in 1988. Only ten hectares were treated with vermiculite applied at the bottom of the furrows, and the rest of the farm treated no vermiculite.

"Fertilizer was applied in a similar way all over (NPK 4-30-10), at the rate of 220 kg/ha. The plot that had vermiculite showed a production of 1.575 kg/ha as against 1.221 kg/ha. This means an increase of 29% in productivity!"

Quotes and information from a presentation to the Vermiculite Association in October 1990.

India

A Field of Rice Grown with Perlite (India)

In India, perlite has been used very successfully both in athletic fields (see EFFECTIVE WATERING WITH HORTICULTURAL PERLITE ) and now in agricultural field crops.

In the often dry state of Gujarat, farmers face the problem of long dry seasons, and very poor and very scarce water for irrigation, and very expensive chemicals. Following up on what they had heard being done in Brazil and in Israel, several experiments were conducted in the mid 1990's to test the use of a very small amount of very fine perlite in sorghum and rice crops.

About 15 farmers were used in a government sponsored series of test. In each case, the farmers were asked to use perlite only in some fields or rows, so that a comparison between areas treated with perlite and those without could be easily made.

After the first season, the results seemed very good. Germination in the perlite areas was 100%; the fields were "thick" with crops and yields were improved.

Here are a few of the comments made by those testing and using perlite in their field crops:

• "The function (of perlite) was remarkable in places where water holding capacity of the soil is poor and the farm is rainfed"
• Twenty-one out of 37 farmers had increases in productivity of more than 10% with crop such as cotton, tur, and caster; these farmers felt the improvements were caused by the addition of perlite.
• Ten out of the 37 farmers had increases in productivity of more than 10% and up to 50%.
• Four farms had yields approaching a 100% incease in yield.