ORGANIC FERTILIZERS AND WOOD ASH IMPACT ON GROWTH OF ENERGY CROPS IN PEAT A LABORATORY STUDY

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1 ORGANIC FERTILIZERS AND WOOD ASH IMPACT ON GROWTH OF ENERGY CROPS IN PEAT A LABORATORY STUDY Latvia University of Agriculture dagnija.lazdina@silava.lv Abstract Willows (Salix sp.) and reed canary grass (Phalaris arundinecea L.) (RCG) are fast growing perennial energy crop and potential cultures for recovering of cutaway peat lands. Cut away peat land soils are characterized by high acidity +1 (ph KCl 2-3), high NH 4, and lack of P and K. Wood ash could be good liming agent and resource of potassium. Waste water sewage sludge (WWSS) compost is effective fertilizer and source of phosphorus. The objective of the study was to investigate the effect of application of WWSS compost and wood ash fertilizers of different doses on ingrown of willow cuttings and RCG in potted cultures. The wood ash addition of 10 g l -1 and 20 g l -1 to WWSS compost mix with peat from used query in proportions 1:1 and 4:1 were tested. The length of shoots and dry mass of shoots and roots were assessed to determine the effect of fertilization on growth of crops. Chemical analyses of growing media were performed to determine the content of main nutrient elements and ph KCl changes during season. The positive effect of fertilization on growth of crops was observed an optimum dose for willows is (10 g l -1 ) equivalent to 10 t DM wood ash with mix of WWSS compost with peat. RCG produces more biomass in growing media containing largest doses of wood ash and WWSS compost premix. The willows produced bigger amount of biomass and accumulated more nutrients from growing media than RCG. Key words: peat, fertilization, willow, reed canary grass, organic fertilizer, wood ash, compost. Introduction In Latvia are available large amounts of waste water sewage sludge (WWSS) to be used as fertilizer for plantation forests according to EU Soil policy (LVA, 2007). Cut away peat lands with thick peat layer in Riga region belongs mainly to Rīgas meži Ltd. Now areas are set-aside lands and municipality are looking for the best way to manage these areas. These studies are model of possible ways of ameliorating of such kind of areas. Willows and reed canary grass (Phalaris arundinecea L.) (RCG) are perennial crops with very short rotation period. It is possible to get biomass for energy from RCG in the first year, but maximum of yield is the second year. The next five years yield is less or more stabile; only after every 7 years it is necessary to re-establish plantations. Yield of RCG is about 4 7 t DM of biomass. Willows have a three year harvesting cycle; average productivity should be at least 9 t DM (Ericsson et al., 2006). Soils of peat lands are usually acid with good supplement of N, but there is a K and P deficit. WWSS contains P, but it is necessary to use minerals or wood ash for K supply and liming of soil in peat (Hytonen, 1998). Willows (Salix sp.) are adapted to wide growth conditions, but acid and wet soils with low aeration are less suitable for willows. Cut away peat lands with thick peat layer usually are too acid for willow cultivation (Hytonen, 1995; Hytonen, 1998; Tahvanainen and Rytkonen, 1999; Puttsepp 2004). Willows are adapted to neutral soils, for production of biomass, and a high supplement of phosphorus and potassium is necessary. Wet and nitrogen rich mires have developed a potassium deficiency that causes a growth reduction (Kaunisto, 1992). Possibility of fast growing willows species to accumulate in biomass large amounts of nutrient elements (such as N, P and K) it is widely used in municipal waste water treatment plants (Hytonen, 2003; Mathe-Gaspar and Anton, 2005). Willows are widely used for reclamation of quarries and mining sites and for production of energy wood in addition too (Weih, 2004). Finland has large experience in establishing energy wood plantations and is most 165

2 competent in peat land afforestation (Hytonen, 1995; Hytonen and Wall, 1997; Tahvanainen and Rytkonen, 1999). In the late 1990 s, nutrient recycling became current in Finnish forestry because of the requirements of the new environmental legislation and the new landfill directives (Moilanen et al., 2004). Use of WWSS and wood ash as the fertilizer for areas reclamation before cultivating fast growing tree species plantations solve different problems: it is a way of environmentally friendly utilization of municipal waste by recycling organic and mineral matter and improvement of soil chemical properties before cultivation of plantations, at the same time decreasing the established cost (Gemste and Vucans, 2006). In Poland, initiative of growing willow plantations comes from waste water sludge producers and managers. In Latvia these questions are still in the initial stage (Лаздиня и др.; 2006, Lazdiņa et al., 2007). In Poland, the main reason for WWSS use as the fertilizer in willow plantations is lower price of sludge compared to minerals (Komorowski et al., 2005). The effects of water soluble K and N fertilizers are faster but of shorter duration than those of P fertilization only years on nitrogen rich sites (Kaunisto, 1992). Wood ash is a good alternative to commercial P and K fertilizers in drained pine mires. Stand nutrient status and growth are enhanced over a longer period of time than with commercial P and K fertilizers (having phosphorus as raw phosphate and potassium as KCl) on both nitrogen rich and nitrogen poor sites (Moilanen et al., 2004). In Latvia, wood ash and WWSS are easy available and could compete with minerals. The year 2008 is the first year when owners of abandoned lands could get support for willows plantation establishing. The interest in WWSS and wood ash usage as fertilizer for fast growing woody crops comes from small municipalities of Latvia. During the last ten years, suitability of wood ash for forest fertilization and cut away peatland reclamation has been studied in the Baltic States and Nordic countries. In Lithuania it was observed that a wood ash dose of 5.0 t changed the chemistry of forest litter and increased ph, and total concentrations of most of the macronutrients were found after 2 years. In contrast, total N concentrations decreased due to ash application. Wood ash increased the number of ammonifying, denitrifying microorganisms and cellulose decomposers in the forest litter 3 months after application. Wood ash slightly reduced total length of fine roots and number of root tips 1 year after treatment. The highest degree of fine roots vitality was found in the plots treated with highest doses of wood ash. No changes in ground vegetation diversity were found after the wood ash and N application (Ozolinčus et al., 2007). Like wood ash, small doses of WWSS 3-5 t DM are recommended in the present studies in Latvia and Lithuania, because, depending of treatment technology, the dry solids of sludge may contain g kg -1 of nitrogen and g kg - 1 of phosphorus. The WWSS and compost may also be used as a fertilizer in tree nurseries and in green lining of towns and cities (Gradeckas et al., 1998; Kāposts et al., 2000). Scientists of the Latvia State forest research institute Silava have good experience of WWSS usage in afforestion of unfertile sites and dunes. Optimal ais application of 3-4 kg per planting spot directly on spot. Growth of trees increases by 30-60%, and application improves survival of trees (Kāposts et al., 2000). Colleagues from Lithuania have similar results that utilizing of sludge in cut away peat lands for growing forests on short rotation along with willows, deciduous trees and their hybrids is very perspective. The biomass productivity of the most perspective tree species in the fifth year of growth reached 12.9 t DM h -1 and is not less than necessary biomass increment for willow plantations. Fertilization is necessary for improvement of peat soil, and the cheapest fertilizer is waste water sludge. Such kind of fertilizer contains heavy metals. Peat possesses bigger absorbing properties of heavy metals than mineral soils, and stops them from migration into deeper soil layer and ground water (Gradeckas et al., 1998). Composts of WWSS contain less heavy metals and has less hygienic risk. Composting is one of the oldest solid waste treatment methods, and the principles of composting process is well known. From the environmental point of view, it is not a good policy to transport biodegradable material from one site to another for storage. To minimize the generation of waste, it is necessary to study composting as solution to recycle organic and mineral nutrient elements (Veijalainen et al., 2007). The objective of the study is to investigate the effect of application of WWSS compost and wood ash fertilizers of different doses on ingrown of willow cuttings and RCG in potted cultures and changes in the content of main nutrient elements and ph KCl in growing media during vegetation season. 166

3 Materials and Methods In current paper, the impact of different doses of waste water sewage sludge (WWSS) compost mix with peat and wood ash on fast growing willow ((Salix schwerinii x S. viminalis) x S. viminalis) clone Torhild and reed canary grass (Phalaris arundinecea L.) (RCG) biomass production and substrate chemical properties changes of the main nutrient elements N, P and K during the vegetation season had been studied. Different substrates were mixed from wood ash (ph KCl 12) from a small boiler house and WWSS compost (N 16 g kg -1 ; P 205 g kg -1, and K 61 g kg -1 ) taken from Meliorators J Ltd. blend with peat from cut away peat land were made. 167 Seven different substrate variants were tested during the vegetation season of 2006 and The experiment was done in potted culture with 3 l of substrate. Four - 20 cm long - cuttings of Torhild were planted in each pot, in total 60 cuttings in 15 pots for each variant. In six pots for each variant, 20 seeds of RCG were sown, in total 120 seeds for all variants (10 kg ). Peat (T) from cut away peat land - turbary -was mixed with WWSS compost (Ko) in proportions 4:1 and 1:1, and then wood ash (A) was added in doses equivalent to 10 t DM or 20 t DM (Table 2). Substrate mixes of potted cultures (willow clone Torhild and RCG) T T4Ko1 T4Ko1A10 T4Ko1A20 Control peat four portions a peat with one portion of compost four portions a peat with one portion of compost with wood ash (10 g l -1 ) equivalent to 10 t DM T1Ko1 T1Ko1A10 T1Ko1A20 peat and compost in equivalent doses peat and compost in equivalent doses with wood ash (10 g l -1 ) equivalent to 10 t DM The experiment was carried out in Olaine nursery. Substrate samples were collected in May before establishing and in September after finishing of the experiment in 2006 and Chemical analyses of N, P, K, and ph KCl were done in Latvia State forest research institute Silava Soil laboratory. Soil acidity (ph KCl ) was tested according to LVS ISO In the laboratory, substrate samples were dried (< 40 ºC), milled and sieved through 2 mm sieve according to LVS ISO standard. Sieved samples were mixed for testing of chemical properties. In dried samples were tested: ammonium form of nitrate N-NH 4 by colorimetric method with Nesler reagent in 0.1 n NaCl extract (Pāvule, 1978; LVS ISO/ TS ); plant nutrient elements phosphorus (P) by colorimetric method in 0.2 n HCl solution (Manual IIIa, 2003); and potassium (K) by Atomic Absorption Spectrometer in CH 3 COONa solution (An Analyst User Manual CD, 2004). Growth of willow clone Torhild was characterized by the height increment and dry matter of shoots and roots during the vegetation season every two weeks and in the end of vegetation season. Dry mass of RCG was determined at the end of vegetation season. Sprouts and roots were dried till constant Table 1 four portions a peat with one portion of compost with wood ash (10 g l -1 ) equivalent to 20 t DM peat and compost in equivalent doses with wood ash (10 g l -1 ) equivalent to 20 t DM mass in 100 C in thermostat and then weighted. Means were compared for significant difference at 0.05 level. The survey was done in October of 2006 and Data statistical analysis T-test, one way ANOVA, and correlation analysis were done by software SPSS. Data statistical analysis by Kolmogorov-Smirnov test approved the normality of data distribution. Results and Discussion The previous experiments hadshowed that limiting factor for willows and reed canary grass (Phalaris arundinecea L.) (RCG) in cut away peat areas are soil acidity and lack of potassium and phosphorus (Lazdina et al., 2007). It was observed that large doses of wood ash neutralize peat acidity as well as enriche it with nutrient elements, wood ash application significantly increases soil extractable phosphorus, potassium, calcium, and magnesium concentrations (Park et al., 2005). In current laboratory study, both wood ash applications stimulated growth of perennial fast growing energy crops, and addition of compost had positive effect too.

4 The addition of WWSS compost to substrate had lees effect on ph value than combination of wood ashes and compost. During vegetation season, acidity of substrate without addition of wood ash slowly decreased, especially in top layer of substrate. Wood ash addition significantly decreased acidity of substrates. Wood ash premix stabilized ph value of substrate, which could be the effect of ash buffer trait (Figure 1). 8 ph KCl ph week Figure 1. Changes in ph of substrate: KCl T; T4Ko1; T4Ko1A10; T4Ko1A20; T1Ko1; T1Ko1A10; T1Ko1A20; T top. WWSS compost premix neutralizes peat till optimum ph for most of Latvia s deciduous tree species, including willows. Premix of wood ash equivalent 20 t DM had alkaline effect on all substrates. The mix of composts and peat in similar proportion with premix of ash equivalent 10 t DM had a similar effect (Figure 1). Studies of other scientists show that wood ash applications in Salix purpurea 3 - year - old plantations significantly increased soil ph in the 0-10-cm soil layer from 6.1 in the control to 6.9 and 7.1 in the 10 and 20 t treated plots (Park et al., 2005), like in our experiment. RCG produced more biomass in pots with enriched substrate, above - ground biomass production did not correlate with higher doses of wood ash and addition of WWSS composts. It was observed that correlations between wood ash addition and decreasing of root dry mass were the same as in woody crop experiments (Figures 2 and 3). DM, g T T4Ko1 T4Ko1A10 T4Ko1A20 T1Ko1 T1Ko1A10 T1Ko1A20 Figure 2. Dry mass (DM) development of RCG at the end of vegetation season: above ground DM g; root DM g. Roots of willow clone Torhild cuttings planted in peat (control) were allocated only in top layer of substrate. In the top of control substrate, ph KCl achieved almost 5, which is more optimal for root development. In alkaline substrates (wood ash - 20 t DM ), a lot of roots were allocated in the bottom of pot. Lithuanian scientists have found that wood ash reduces total length of fine roots and number of root tips 1 year after treatment in pine stands (Ozolinčius et al., 2007). We found similar tendency in root developing of willow cuttings with wood ash additive in some variants. A gregter effect of wood ash premix on willow clone Torhild shoot growth than on root development was obserwed (Figure 3). 168

5 20 Shoots 20 Roots g 10 g week week Figure 3. Dry mass (DM) development of willow clone Torhild shoots and roots during vegetation season: T; T4Ko1; T4Ko1A10; T4Ko1A20; T1Ko1; T1Ko1A10; T1Ko1A20. WWSS composts and wood ash during vegetation season stimulated growth of willows, but differences were significant only between control and other variants. Faster growth of willow shoots was observed in substrates with wood ash addition (Figure 4). Figure 4 demonstrates mean data of shoot growth during season. Irregularity of trends could be explained by withering and rushing up of sprouts during summer. cm week Figure 4. Average height of willow sprouts during the vegetation season: T; T4Ko1; T4Ko1A10; T4Ko1A20; T1Ko1; T1Ko1A10; T1Ko1A20. At the end of vegetation season, there significant differences in sprout count from cutting among different variants (P<0.001) were observed but not among sprout height(figure 5). Production of more sprouts from willow cuttings in substrates with wood ash premix explain why more biomass were produced in such growth conditions. Willow clone Torhild had only one sprout from cutting in most cases of the control variant, but addition of WWSS compost lead to increase of sprout count from 2 to 3, which is optimal for energy crop cultivation. Average sprout count increased when wood ash was added - in these variants each cutting produced 4 or more sprouts. An opposite effect has been found by other scientists in the experiment with wood ash fertilizing in USA; increase of size of stems of Salix purpurea; however this effect was balanced by a decrease in the number of stems (Park et al., 2005). Willows in field conditions had tendency to produce larger amount of sprouts on alkaline soils, substrates with wood ash premix were more alkaline, and willow cuttings produced more sprouts, like in field conditions. Significant correlations between willow sprouting and content of phosphorus, potassium, and peat acidity (Table 2) were observed, but no correlations were found between shoot height and substrate chemical properties. 169

6 Table 2 Willow shoots growth, substrate ph and macronutrients Pearson correlations (N=255) Height, Number InitiallN, InitiallyP, InitiallyK, Initially Final N, Final P, Final K, cm of g kg -1 g kg -1 g kg -1 ph KCl g kg -1 g kg -1 g kg -1 sprouts Final ph KCl Height cm Number of sprouts ** ** ** ** ** ** Initially N, g kg ** ** ** ** ** ** ** ** Initially P, g kg ** ** ** ** ** ** ** ** Initially K, g kg ** ** ** * ** Initially ** ** ** ** ** ** ** ph KCl Final N, g kg ** ** ** ** ** ** ** Final P, g kg ** ** ** * ** ** ** ** Final K, g kg ** ** ** ** ** ** ** ** Final ph KCl ** ** ** ** ** ** ** * Correlation is significant at the 0.05 level (2-tailed). ** Correlation is significant at the 0.01 level (2- tailed). Sprouting of cuttings had negative correlation with potassium in substrates at autumn, and rushing of sprouts lead to decreasing of potassium in substrates. There were observed Negative correlations between nitrogen and phosphorus content in substrates were observed in spring. Substrates were mainly enriched with phosphorus with WWSS and wood ash addition. Positive spring correlations of phosphorus and soil alkalinity could be explained by presence of element in ash and compost. At the end of vegetation season, significant changes in nitrogen, and phosphorus content in substrates (P<0.001) as well as in proportions of N, P and K (Figure 5), especially in top layer of peat (control), were observed. autumn 80% 40% 0% % 40% 0% T T4Ko1 T4Ko1A10 T4Ko1A20 T1Ko1 T1Ko1A10 T1Ko1A20 T T4Ko1 T4Ko1A10 T4Ko1A20 T1Ko1 T1Ko1A10 T1Ko1A20 Figure 5. Macronutrient (N, P and K) content and proportion changes during the vegetation season: N g kg-1 P g kg-1 K g kg-1 N g kg -1 ; N g kg-1 P g kg-1 K g kg-1 P g kg -1 ; N g kg-1 P g kg-1 K g kg-1 K g kg

7 Plants had been uptaken nutrients for biomass production, especially nitrogen. In some substrates, potassium content in autumn was observed higher than in spring. Tendency o plants to accumulate nutrients in roots before the cold season to reach higher cold resistance and presence of necrotic tissues of roots in substrates could explain higher concentration of potassium in some substrate samples. Above - ground biomass of willow shoots and substrate phosphorus concentration showed positive correlation, RCG above - ground dry mass correlated with substrate acidity, but root dry mass - with amount of phosphorus (Table 3). Compost Table 3 Willow and RCG biomass accumulation and substrate properties Pearson correlations Above - ground Root, N, P, K, Wood ash biomass, DM g g kg -1 g kg -1 g kg -1 ph DM KCl addition addition Willow clone Torhild Above ground biomass, DM g * Root, DM g RCG Above - ground biomass, DM g * Root, DM g * * Correlation is significant at the 0.05 level (2-tailed) Despite the well known fact that potassium is the element most affected by wood ash treatment at all soil depths (Park et al., 2005; Ozolinčus et al., 2007), no significant effect of this element was observed. Wood ash and composts are sources of phosphorus - this could be one of the reasons why we observed higher biomass production in substrates where combination of both fertilizers was used. In Finnish research papers, wood ash is mentioned as one of cheapest and most effective sources of phosphorus for long term effect (Hytonen, 1998; Hytonen, 2003; Moilanen et al., 2004). Results of the research allow drawing up a conclusion that WWSS composts and wood ash application and digging into soils of cut away peat lands could be good solution of waste management and biomass production for green energy. Conclusions 1. Soils from abundant peat cutaway areas are too acid for cultivation of perennial crops - willows and reed canary grass. 2. Addition of WWSS compost to peat in similar proportions decreased soil acidity for 1 2 units. Addition of wood ash (doses equivalent to t DM ) decreased substrate acidity for 3 4 units. 3. WWSS composts, wood ash and peat mix are suitable substrate for growing of willows and RCG. In cutaway peat areas, WWSS composts and wood ash must be ploughed into soil. Surface fertilizing is ineffective. 4. Wood ash and WWSS compost different proportions show significantly different effect on willows shoots and roots development and production of RCG biomass. 5. The best combination was the mix of peat with WWSS compost in similar doses and 10 g l -1 ( equivalent to 10 t DM ) of wood ash, but production of RCG biomass was significantly stimulated by 20 g l -1 ( equivalent to 20 t DM ) of wood ash. 6. The content of phosphorus correlated with RCG root biomass, willow shoot height and biomass, but substrate acidity correlated with RCG browse biomass. Acknowledgements Research work was done with the support of Ministry of Education research project Top-07-15, European Social Found. 171

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