Z. Henkin et al., SOIL-PHOSPHORUS IN A MANAGED MEDITERRANEAN WOODLAND ECOSYSTEM - HERBAGE RESPONSE AND CATTLE GRAZING EFFECTS, Agriculture, ecosystems & environment, 47(4), 1994, pp. 299-311
A study of soil-plant relations in scrub woodlands on terra rossa soil
in Israel, examined the following hypotheses: (a) that herbaceous pla
nt growth on terra rossa is limited by phosphorus deficiency; (b) that
shrub control and tree thinning can release available P for use by he
rbaceous vegetation; (c) that cattle fed P-rich poultry litter as a ni
trogen supplement, can increase the available P level in the soil by r
ecycling excess P through their excrements. Soil available P (bicarbon
ate-soluble) content was 4-9 mg kg-1 soil in the surface 15 cm soil la
yer and 2-3 mg kg-1 soil in the deeper 15-30 cm layer. A bioassay show
ed that plant growth was restricted when P concentration was less than
11 mg P per kg soil. Addition of nitrogen did not increase herbaceous
yield, Neither thinning of trees nor shrub control using herbicide ha
d any significant effects on available soil P. There was a significant
increase in available soil P concentration in the surface 3 cm layer
of soils on sites that had been partially cleared and grazed for 3 yea
rs by cattle supplemented with poultry litter. Only near centers of ca
ttle activity was there a significant increase of P in the 3-15 cm lay
er, and only there was the enrichment sufficient to remove phosphorus
limitation to herbage growth.