The Effects of Living Mulches on Tuber Yields of Potato.

N. S. Boyd¹, R. Gordon², S. K. Asiedu³, and R. C. Martin³

The adverse effects of long term soil erosion on potato production are well established, and living mulches are one option organic farmers have for reducing erosion in potato fields. Living mulches are typically grass or legume crops that are intercropped (i.e. grown simultaneously) with a cash crop. In terms of crop management and soil quality living mulches have several benefits:

• they help reduce erosion by keeping the soil covered and reducing the velocity of wind and water before they reach the soil;
• by covering the soil they also reduce soil moisture loss and provide competition for weeds;
• when ploughed under living mulches return nutrients and organic matter to the soil. This helps maintain soil structure and further reduces the risk of erosion; and
• if all or part of the living mulch is a legume, they also improve soil fertility by fixing atmospheric nitrogen.

However, while the use of living mulches may help reduce erosion rates, improve soil structure and fertility, and reduce weed competition, there is a potential trade-off in that they may also compete with the crop for nutrients, water, etc.

To study this potential trade off more closely in potato production, researchers at the Nova Scotia Agricultural College in Truro, NS conducted a 2-year trial in 1997 and 1998. The various treatments they used each year are summarized in Table 1. Each of these treatments was evaluated on two potato varieties (Russet Burbank and Island Sunshine) in both years.

Table 1. Treatments for living mulch trials - 1997, 1998:

In addition to plant development and tuber yields, the research also looked at the effects of the living mulches on soil moisture. The results of these trials showed that:

• Tuber yields were not significantly different when managed organically or conventionally. In both years soil moisture levels remained consistently lower in conventionally managed plots than in the organic plots planted with living mulches. However, since moisture levels were not monitored in the organic plots managed with no living mulch, there was no way to tell if this was due to the effect of the mulches or to the addition of manures to the organic plots.
• Of the living mulches, only the intact native sod adversely affected plant development and total tuber yields. Since the other living mulches were planted after hilling, the time for competition between the living mulches and the crop was reduced and plant development and tuber yields were not affected.
• Planting the tubers under a layer of straw or hay also affected plant development and decreased tuber yields. Although hay or straw mulches tended to result in increased soil moisture levels, plant development and yields were most likely affected by decreased soil temperatures in the early part of the growing season.
• Planting in raised beds reduced the yield of Canada No. 1 tubers in 1998, especially on the inside rows. This was because the closer plant spacing increased competition for soil nutrients.

Researcher Locations & Affiliations:
(1) Department of Plant Science, University of Manitoba
(2) Department of Engineering, Nova Scotia Agricultural College, P.O. Box 550, Truro, NS B2N 5E3
(3) Department of Plant and Animal Sciences, Nova Scotia Agricultural College, P.O. Box 550, Truro, NS B2N 5E3


Reference:
Boyd, N.S., R. Gordon, S.K. Asiedu and R.C. Martin. 2001. The effects of living mulches on tuber yields of potato (Solanum tuberosum L.). Biological Agriculture and Horticulture, 18: 203-220.


Related Links:
The link below provides a summary of the various methods used to prevent erosion and manage soil water and nutrients in organic farming:

Conservation Tillage and Organic Farming - Mutually Exclusive?
Av Singh, Organic Agriculture Centre of Canada


en français