Field evaluation of the "Bait-lamina test" to determine the soil microfauna feeding activity
The soil microfauna regulate nutrient cycling through predation on soil microorganisms but also through comminution of organic residues in soils. The feeding activity of the soil microfauna has a large impact on nutrient cycling and soil function, but is rarely considered because it is difficult to assess. The Baitlamina test was proposed as a practical mean to assess microfauna feeding activity. The test consists of vertically inserting 16-hole-bearing plastic sticks stuffed with a plant material preparation into the soil. We tested if the plant material used to prepare the bait would be differentially utilized by microfaunal population present under different plant species or mixtures of plants. We evaluated the Bait-lamina test in a 5-year old field experiment with five levels of plant communities (monocultures of Russian wild rye, switchgrass, green needlegrass, or western wheatgrass, and a grass mixture) distributed in four complete blocks, using six levels of bait flavour (Russian wild rye, switchgrass, green needlegrass, western wheatgrass, alfalfa, and wheat bran). Bait-lamina strips were equally spaced at five locations between plant rows. We found that the bait flavour had no significant (P = 0.22) effect on feeding, although the concentration of crude protein in the plant material used in the baits varied (P = 0.006) from 2.9% in switchgrass to 5.9% in Russian wild rye. We found low feeding activity in our field plots over the period of the test ( 13 June to 17 August 2005), with only 2.7% of the lamina (hole stuffing) showing signs of feeding. The data nevertheless revealed that microfauna feeding was more important close to the soil surface (0.5 mm deep), and in Russian wild rye plot mid-rows as compared to green needlegrass or switchgrass plots. Closer to plant rows, however, differences were not significant. We conclude that bait prepared with any plant material used in this study can be used to compare microfauna feeding in different plant stands. We recommend the use of a large number of replicated strips in agricultural field experiments where the microfauna may be scarce.
soil biological activity
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