Antti Wall

Soil fertility of afforested arable land compared to continuously

In Finland, over 220,000 ha of arable land has been afforested in recent decades. To meet the goals of forest management on afforested fields, information on the effects of former agricultural land use on soil fertility is needed. In this study, we examine the soil fertility of 12 former arable fields afforested either 10 or 60–70 years ago with Norway spruce (Picea abies (L.) Karst.) and adjacent sites that have been forested continuously. Volumetric soil samples were collected from the organic soil layer and from mineral soil to a depth of 40 cm. Soil samples were analyzed for pH, bulk density, organic matter content and amounts of nutrients (Kjeldahl N, extractable P, K, Ca, Mg, Zn and B). On afforested fields, amounts of nutrients in the mineral soil, especially in 10-year-old afforestations, were higher than on continuously forested sites. In the organic layer plus the 0–40 cm soil layer, the 10-year-old afforestations had 68% more N, 41% more P, 83% more K, 252% more Ca, 6% more Mg, 61% more Zn and 33% more B than the continuously forested sites at a comparable soil depth. In the 60–70-year-old afforestations, the differences were significant only for N, Ca and Zn (20% more N, 121% more Ca and 115% more Zn than on the continuously forested sites). The effects of agriculture on amounts of nutrients were most clearly detected in the former plough layer (0–20 cm) of the 10-year-old afforestations and in the top layer (0–10 cm) of the older afforestations. Amounts of nutrients in the organic layer of the afforested sites were lower, but their concentrations were higher than in the continuously forested sites. On the 10-year-old afforestations, the bulk density of the mineral soil tended to be lower and the organic matter content higher than on the continuously forested sites. On both young and old afforestations, soil pH was higher than on the continuously forest sites. According to these results, changes in soil properties caused by agriculture have increased the soil fertility and therefore probably also the site index. The results also suggest that changes in soil properties due to agricultural land use are quite long lasting.

Water-retention characteristics and related physical properties of soil on afforested agricultural land in Finland

Abstract In recent decades, afforestation of agricultural land in Finland has caused a substantial change in land use. To assess the potential of such former agricultural soils for production of tree crops, information on soil properties is needed. The water-retention characteristics (WRC), bulk density (BD), organic matter (OM) concentration and particle-size distribution were studied in soil on afforested agricultural land in western Finland. Sites with an OM

Effect of Air-filled Porosity and Organic Matter Concentration of Soil on Growth of Picea abies Seedlings after Transplanting

The effects of air-filled porosity (AFP) and organic matter concentration (OMC) of soil on the growth of Norway spruce [Picea abies (L.) Karst.] seedlings were studied in a greenhouse experiment. One-year-old seedlings were planted into 250 pots filled with five different growth media based on low-humified sphagnum peat and fine sand. The media were mixed to achieve five levels of OMC (1, 25, 50, 75 and 97% by mass). Five AFP levels (5, 10, 20, 30 and 40%) were applied to the mixtures of growth media during irrigation. The growth attributes of the seedlings were measured after seedlings had grown in the greenhouse for 15 weeks. The shoot height and mass growth as well as root mass were significantly higher in 20, 30 and 40% AFP than in 5 and 10% AFP (p<0.05). The longest shoots were produced in growth media with 25, 50 and 75% OMC (p<0.05). The effect of OMC on root mass, while significant (p=0.03), was less pronounced than the effect on height growth and mass of the shoots (p<0.001). The results indicate that, for good seedling growth in pots in greenhouse conditions, AFP should be 20-40% and OMC 25-75% in the growth medium.

Loss‐on‐Ignition in the Determination of Pools of Organic Carbon in Soils of Forests and Afforested Arable Fields

Abstract Loss‐on‐ignition (LOI) and concentration of organic carbon (Cc) were determined on pristine forest soils and soils from afforested arable fields. The objectives were to investigate the relation between the Cc of soil estimated indirectly from LOI and true Cc from dry combustion (CLECO) and further to evaluate how the applied analytical method affects the carbon pool estimates. According to results, LOI was a good indicator of Cc in the organic layer. As regards mineral soil, however, CLECO/LOI ratio significantly decreased with increasing depth, and the ratio changed differently in soils underlying forest sites as opposed to the soils from former fields. The results indicate that estimation of carbon pools from conversion factors would lead to considerable bias and that direct measurement of Cc is preferable to the use of any Cc/LOI ratio. The results also emphasize the need for elimination of carbonate carbon when measuring Cc from the soil of arable fields.