Comparison of hay vs. grass mulch on lettuce production in no-dig beds

Figure 1: Photo of part of the no-dig trial site

Figure 1: Photo of part of the no-dig trial site

Comparison of hay v grass mulch on lettuce production in no-dig beds

by Kitty Scully

This study used beds which had been operated under a no-dig system for a number of years (Figure 1).

To produce conditions suitable for the crop, a deep mulch of either hay (3 kg/m2, 65 mm deep) or grass (6 kg/m2, 50 mm deep) was applied to the surface of the beds (sandy loam soil) on 1 June 2013.

The grass mulch resulted in much larger yields of butterhead lettuce than did the hay mulch (Figures 2 and 3). This effect was associated with a significant increase in available nitrogen in the soil under the grass mulch (25.3 ppm) compared to that under the hay mulch (7.6 ppm), as well as a higher soil moisture content in the site under a grass mulch. The lettuce plants reached a marketable size earlier under grass mulch and this effect could enable growers to achieve a higher number of crops per growing season.

Figure 2. Median fresh weight of butterhead lettuce heads  grown with hay or grass mulch

Any two medians with a common letter are not significantly different (P>0.05)

Figure 2. Median fresh weight of butterhead lettuce heads  grown with hay or grass mulch

 

Figure 3. Differences in size of  lettuce heads from no-dig beds mulched with hay (left) or grass (right)

Figure 3. Differences in size of  lettuce heads from no-dig beds mulched with hay (left) or grass (right)

 

No significant differences were observed between earthworm numbers in sites which were mulched with hay or grass or were unmulched (Figure 4), although the proportion of juvenile earthworms was highest in the control sites. No significant difference in numbers and diversity of soil bacteria was noted between the two mulched sites.

 

 Figure 4. Presence and absence, and type of mulch on earthworm numbers.

Any two medians with a common letter were not significantly different (P>0.05)

Figure 4. Presence and absence, and type of mulch on earthworm numbers.

Centre for Organic Horticulture Research

School of BEES, Butler Building, Distillery Field, North Mall, Cork

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