Juha Heiskanen

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

Physical properties of two-component growth media based on Sphagnum peat and their implications for plant-available water and aeration

The physical properties, in particular the water retention characteristics, of two-component growth media based on low-humified Sphagnum peat were studied. The high water retention of pure peat, which is further increased by shrinkage of the medium at desorption, yielded low air-filled porosity at high matric potentials (≥ −1 kPa). The addition of coarse perlite to peat decreased the shrinkage markedly and also tended to increase the low saturated hydraulic conductivity of peat, which had initially been rather low. In all media studied, the amount of water that is easily available to plants (water content retained between −1 and −10 kPa matric potential) was relatively high. In peat that contained half repellent rockwool or hydrogel, this water retention was, however, markedly lower. Between −10 and −50 kPa matric potential, water retention was rather low in all media (< 10%). Within the lowest matric potential range studied (−50 to −1500 kPa), water retention was considerably elevated in peat that contained half hydrogel. The implications of the physical properties of the media for plant-available water and aeration in the media are discussed.

Favourable water and aeration conditions for growth media used in containerized tree seedling production: A review

The importance of soil water and aeration conditions on the growth of containerized tree seedlings in conjunction with the physical properties of various growth media used are reviewed and discussed. Favourable water and aeration conditions in these different growth media are described and some implications for the Nordic production of containerized tree seedlings are considered. It is concluded that matric potentials of > — 50 kPa and oxygen diffusion rates > 70 μg m‐2 s‐1 in the growth medium should be achieved during the growth period. Light, low humified Sphagnum peat, which is the most commonly used growth medium in the Nordic countries, provides favourable growth conditions in the greenhouse. However, when these growth conditions are not properly managed, light peat may not favour good seedling growth. Seedling hardening and outplanting phases are critical for outplanted seedling success, but little control can be exerted over them. Thus the physical properties of growth media should be evaluated an...

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.

Irrigation regime affects water and aeration conditions in peat growth medium and the growth of containerized Scots pine seedings

Containerized Scots pine seedlings growing in light Sphagnum peat growth medium in a greenhouse were subjected to three irrigation treatments. The seedlings were irrigated by saturating the growth medium with a nutrient solution (i) daily or when (ii) −5 or (iii) −10 kPa medium matric potential was achieved. In general, the nutrient concentrations in the foliage of the seedlings were rather similar for all irrigation treatments. In the wet (daily) irrigation treatment, however, the foliar concentration of N was lower and the foliar concentrations of P, Ca, S, Mn and Na were higher than in the other two treatments. In the wet irrigation treatment, height growth was lower than that in the other treatments. In this treatment the shoot to root ratio and several other morphological characteristics were also reduced, while the number of root lenticels and seedling mortality were increased compared to the other treatments. Rapid growth was obtained by irrigating at −5 to −10 kPa matric potential. In the wet irrigation treatment, the median matric potential and air-filled porosity of the peat medium were −0.4 kPa and 11%, respectively, which indicated waterlogging and very suboptimal aeration to the seedlings. The respective values for the irrigations at −5 and −10 kPa were −2.7 to −3.3 kPa and 39 to 43%, which were considered to cover the range from optimum to slightly suboptimum for average water availability and aeration.

Autumn Fertilization in the Nursery Affects Growth of Picea abies Container Seedlings After Transplanting

Second-year Norway spruce seedlings [Picea abies (L.) Karst.] grown in containers were divided into three fertilization levels in August [5, 15 and 25 mg nitrogen (N) seedling−1]. The resulting foliar concentrations of N were 11.0, 13.1 and 15.8 g kg−1, respectively. Seedling height (mean 26.0 cm) did not differ among treatments. The next spring, the seedlings were tested in two experiments. (1) The seedlings were transplanted into pots containing sandy soil in the greenhouse, where they were fertilized with either pure water or nutrient solution (22 mg N l−1). (2) The outplanting performance of the autumn-fertilized seedlings was tested on a sandy field. In the greenhouse experiment, the autumn fertilization level affected height growth and root egress of the seedlings significantly, but less than fertilization with a nutrient solution after planting. In the field experiment, during the first season after transplanting shoot growth of the seedlings increased with the level of autumn fertilization. After the second and third seasons, the seedling stem volume was highest with the highest level of autumn fertilization. These results suggest that, by improving the preplanting nutrient status of seedlings, the growth of shoot, stem diameter and root biomass can be enhanced after planting, especially on nutrient-poor soils. However, heavier autumn fertilization than that used here may yield a greater and more persistent increment in growth.

Effects of compost additive in sphagnum peat growing medium on Norway spruce container seedlings

Sphagnum peat has been the most commonly used growing medium in containers in tree nurseries worldwide for its good growing properties. As a result of increasing costs and environmental incentives, seedling-growers are seeking more local growing medium components such as composts. Composts are, however, diverse products with varying chemical, physical, and hygienic properties and therefore require thorough testing before real-world use. In this study, a commonly used compost (raw materials: sewage sludge, biowaste, peat, wood chips) was tested for feasibility as a component (0–30 vol.%) of a sphagnum peat container medium for growing Norway spruce (Picea abies (L.) Karst.) container seedlings in a forest-tree nursery. In proportions of up to 30% in peat, the compost additive used was shown to be a feasible material for seedling growing in forest nurseries. On average, the seedlings grew best in pure peat, but the compost additions to peat showed no marked reduction in seedling growth in greenhouses, nor were there any effect on seedling growth in the first summer after outplanting. However, a slightly elevated risk of seed non-germination and of seedling mortality was observed when the growing media contained compost in proportions of 20% or more. The compost additive in peat also changed the bulk density, structure, and chemical properties of the medium during nursery growing. The results suggest that seedling watering and fertilisation should be adjusted for each growing medium mix separately to achieve correct water, oxygen, and nutrient availability in containers during nursery growing.

Hydrological Properties of Container Media Based on Sphagnum Peat and their Potential Implications for Availability of Water to Seedlings after Outplanting

Abstract Hydrological properties, in particular water-retention characteristics (WRC) and hydraulic conductivity (K), were studied in eight different growth media based on low-humified sphagnum peat with coarse (perlite) and fine (sand) constituents. The temporal change of matric potential (ψ) in the media, which were connected to two contrasting mineral soils (fine and coarse sandy soil) with higher ψ, was studied in the laboratory in order to emulate the hydraulic situation in field conditions after outplanting of container seedlings. It was shown that the hydrological properties of peat medium and its hydraulic interaction with sandy soil can be altered markedly by the additives used. Adding a coarse constituent (perlite) to peat increased air-filled porosity (AFP) and saturated K of the medium, but decreased water retention (WR) (especially in wet conditions) and unsaturated K. Addition of a fine constituent (sand) decreased AFP and saturated K, but increased WR and K in dryish conditions. In general,...

Influence of different nursery container media on rooting of Scots pine and silver birch seedlings after transplanting.

Scots pine (Pinus sylvestris L.) and silver birch (Betula pendula Roth.) seedlings were grown in containers filled with growth media based on medium-textured sphagnum peat, coarse perlite and fine sand. The seedlings were then planted into fine and coarse sandy soils in 2.2 l pots, which were subjected to two water-content treatments (only one for birch). After the seedlings had grown five weeks in a greenhouse, rooting into the surrounding soil and shoot growth were measured. Addition of perlite and sand to peat medium slightly affected rooting; thus suggesting minor effects on seedling establishment. However, nitrogen concentration of the seedlings varied between growth media and correlated positively with rooting into the soil. The particle size and water content of the soil affected considerably rooting of the seedlings. Seedling height at the time of planting did not affect rooting or shoot growth. The fact that the fewest out-grown roots occurred in the dry fine sandy soil, suggests that dry soil together with high strength and resistance to root penetration reduce rooting and water uptake by container seedlings most and may thus cause water and nutrient stresses to seedlings after outplanting.

Effect of Peat-based Container Media on Establishment of Scots Pine, Norway Spruce and Silver Birch Seedlings after Transplanting in Contrasting Water Conditions

Container seedlings were grown in pure sphagnum peat and peat mixtures containing coarse perlite and/or fine sand 25% by volume. Soil - water availability and rooting of the seedlings into the surrounding sandy soil after transplanting were studied in contrasting soil - water conditions in a greenhouse and a field experiment. No clear benefit was found for seedling rooting and establishment after planting by adding the used constituents to peat container medium. In fact, rooting of pine and birch was greatest in pure peat medium. Weakened seedlings occurred most frequently in media containing fine sand with lower water retention (in the matric potential range ?1 to ?10 kPa) than in pure peat or peat containing perlite. Preplanting and postplanting waterings clearly affected soil - water relations and seedling performance. Wet container media were found to release the most easily retained water into the soil within hours after planting. The amount of water released into coarse planting soil was less than that released into fine soil. Dry container media absorbed water from the soil for several days after planting, but still remained drier for a few days than those watered prior to planting. Preplanting watering decreased the mortality of conifer seedlings, and promoted their rooting into the soil, height growth and needle mass, but did not do so for birch. Postplanting watering did not affect mortality, but it promoted height growth and needle and leaf mass of all three species and rooting of birch. The results emphasize the importance of the water - retention characteristics of container media and of watering seedlings before outplanting for seedling establishment, especially in dry growth conditions.