03.08.2015   Recycling of Biomass Ashes

Results. Soil

Soil pH and Ca, Mg, K, P, and S levels increased slightly after ash application. No leaching loss was observed after several applications of ash. Furthermore, microbial activity increased and ammonium and nitrate concentrations decreased as a conse­quence of N immobilization. No effects due to heavy metals were observed in the soil solution, and the availability of Mn and Zn increased slightly after the third application of ash.

3.3.1 Nutrition

The Pinus radiata plantations were initially deficient in P, K, and Mg (Table 6.4), as often found in this type of acid soil plantation (Mesanza et al. 1993; Romanya and

Table 6.4 Concentrations of nutrient elements in the needles (mg g!)

N

P

K

Ca

Mg

N/P

Lutites

13.4

0.9

4.3

1.3

1.0

18.0

Migmatites

15.0

0.9

5.6

1.4

0.8

17.7

Will (1985) and Lambert (1984)a

15

>1.4

>5.0

>1.0

>1.0

—

Zas et al. (2002)b

16.9

1.1

6.2

2.1

0.8

15.4

Sanchez-Rodnguez et al. (2002)c

16.4

0.8

7.5

1.7

0.7

20.5

WAP wood ash plus P2O2

aOptimal values for Pinus radiata D. Don plantations

bFoliar concentrations in Galicia for Pinus radiata young plantations

cAverage concentrations of nutrient elements in the needles of Pinus radiata plantations on different soil parent material

Vallejo 1996). In contrast, foliar N concentrations were sufficient (15 mg g-1). Repeated application of wood ash to the soil did not have any effect on foliar concentration 3 years after the initial treatment. Although the concentrations of basic cations such as Ca2+ and Mg2+ increased significantly in the soil, foliar analysis did not show any significant changes in the needles after the treatment. This may be the result of tree growth and the consequent dilution effect.

Supplemental fertilization with slow release of phosphorus (WAP treatment) increased the foliar concentration of the element throughout the study (Fig. 6.3). The differences between treatments are more significant for the soils over migma — tites than for those over lutites. However, repeated application of wood ash did not increase the levels of P in needles.