EFFECTS OF EARTHWORM ACTIVITIES ON SOME CHEMICAL AND PHYSICAL PROPERTIES OF A GRASSLAND SOIL AND ON THE GROWTH OF MAHOGANY (SWIETENIA MACROPHYLLA KING.) AND YEMANE (GMELINA ARBOREA ROXB.) SEEDLINGS (MULTIVARIATE ANALYSIS VARIANCE, ORGANIC MATTER).

摘要

The biology and growth pattern of the earthworm Pontoscolex corethrurus Mull. were studied in the laboratory based on single-cultures from cocoon to maturity.; Three earthworm durations of activity (control, 1.5 mo, and 3.0 mo) on potted grassland soil under greenhouse condition and combined factorially with 5 organic matter sources (control, 1:1 rice straw + Leucaena leaves, 2:1 rice straw + Leucaena leaves, 1:1 cogon grass + Leucaena leaves, and 2:1 cogon grass + Leucaena leaves) were evaluated to determine their effects on the chemical and physical properties of the soil including the effects on seedling biomass of two reforestation species. The study was conducted as a factorial experiment in a randomized complete block design. Univariate and multivariate technique of data analyses were used. A total of 28 variables were monitored and evaluated.; In Mahogany plots, earthworm activities significantly affected four soil chemical properties (N, Mg, Fe, and Na), two size-classes of water-stable aggregates (2 mm, and 0.25 mm) and, most of earthworm and seedling biomass variables. Organic matter treatments were significant for five soil chemical properties (pH, N, K, Al, and OM), two size-classes of water-stable aggregates (2 mm, and 0.125 mm) and, all of earthworm and seedling variables.; In Yemane plots, earthworms significantly affected Fe and Na, 2 mm and 0.25 mm fractions of water-stable aggregates, particle density (PD), all earthworm biomass indicators, but none of the seedling variables. The effects of OM treatments were the same as in Mahogany plots.; The earthworm-treated plots were better than controls in some soil properties that were reflected in earthworm biomass indicators but not by seedling performance. The average effect of organic matter additions was better than the control in most soil properties that was also reflected by both earthworm biomass and seedling variables.; Canonical correlation analyses between soil and seedling variables indicate significance for Yemane plots but none for Mahogany plots. Fresh weight had very high loadings on the canonical variables for both species, indicating better representation of seedling performance than height and/or oven-dry weight especially when correlations with variations in soil properties are considered.