Newsletter from Danish Research Centre for Organic Farming • March 2005 • No. 1

Ridge planting of maize shows promising yield increase

By Christian Bugge Henriksen, Jesper Rasmussen,The Royal Veterinary and Agricultural University (KVL), Martin Heide Jørgensen and Henning Carlo Thomsen, Danish Institute of Agricultural Sciences (DIAS)

In 2003 pilot studies with ridge planting of various crops was conducted at KVL and St. Jyndevad Experimental Station (DIAS) as a part of a collaboration between the DARCOF project CARMINA and the project Technological Development in Organic Farming.

A number of interesting observations have been made, and at KVL, where the field studies were conducted with block repetitions, a dramatic yield increase was found when maize was planted on ridges. Soybean also performed well on ridges.

Use of a newly developed ridge planter

Before the 2004 growing season a special ridge planter was constructed at DIAS Research Centre Bygholm (see Figure 1).

Figure 1.
Ridge planter developed at Research Centre Bygholm.

This planter can be used for precision planting on the top of ridges as well as planting of grass on the side of ridges. The planter was tested at St. Jyndevad Experimental Station, where maize, sugar beet and soybean were planted on ridges in spring 2004.

Yield increase in maize

The experiments showed that there are major advantages associated with ridge planting of maize (Figure 2). Ridge planting increased total dry matter yield by 60 pct. from 8.0 ± 0.7 to 12.8 ± 1.5 tonnes per hectare compared with traditional planting on flat soil.

The relative cob yield was 52 pct. with ridge planting and 56 pct. with planting on flat soil.

Figure 2. Maize on ridges (left) grows more vigorously than maize on flat soil (right). Figure 3. Maize on ridges (left) have better developed roots than maize on flat soil (right).

The reason for this dramatic yield increase is not known, but several factors may contribute:

  • use of ridges increases solar absorption and/or wind shelter, which in turn may increase soil temperature, speed up germination and increase early crop growth
  • ridges may increase drainage and reduce water logging
  • looser soil in the ridges and greater soil surface may improve aeration.

If soil moisture is adequate a higher temperature and improved aeration will increase mineralization and thereby improve the supply of nutrients to the crop early in the growing season. In this way it is possible that ridges may serve as an alternative to the starter fertilizer normally used in conventional maize production.

Root observations have shown that maize planted on ridges have a more vigorous root system (Figure 3), so it seems possible that ridges may both increase the availability of nutrients and stimulate root growth. More photos from the maize experiment can be found at the weblog Okologgen (in Danish)

Ridge planting of protein crops

The positive experiences with ridge planting of maize make it relevant to investigate whether other heat demanding crops such as faba bean, soybean and lupin may show similar advantages with ridge planting. In experiments at St. Jyndevad Experimental Station faba bean planted on ridges had a larger root system and bigger nitrogen fixing root nodules than faba bean planted on flat soil. This was also found in soybean, which gave a higher yield when planted on ridges, although the general yield level was very low.

In similar experiments at KVL ridge planting of soybean increased germination compared with planting on flat soil.

Thus, in additions a detailed examination of the reasons for the dramatic yield increases in maize, it is also relevant to investigate whether other row crops may be suitable for ridge planting.

Ridge planting of winter rape

In autumn 2004 a pilot study with ridge planting of winter rape was established at St. Jyndevad Experimental Station. Earlier studies at KVL have shown that ridging in autumn and winter may reduce N leaching and increase the yield of a subsequent crop planted on flat soil. In winter the winter rape will work as a catch crop to further reduce leaching and in spring it will benefit from the growth promoting advantages of ridges. Photos from the pilot study can be found at the weblog Okologgen (in Danish).

Future studies

We now have a functional ridge planter that may be used in future studies and based on the positive results from the pilot studies, especially with ridge planting of maize, we are currently applying for new funds to perform a thorough investigation of the potential for ridge planting in organic farming.