Inorganic NP Fertilizers Research Articles

Evaluation of FYM and Inorganic NP Fertilizers on Yield Performance of Sweet Potato [Ipomoea batatas (L.) Lam] in Debub Ari District, Southwestern Ethiopia

Evaluation of FYM and Inorganic NP Fertilizers on Yield Performance of Sweet Potato [Ipomoea batatas (L.) Lam] in Debub Ari District, Southwestern Ethiopia

Effect of coffee husk biochar and inorganic NP fertilizer on soil properties, growth and yield of potato (Solanum tuberosum L.) on acidic soil of southwest Ethiopia

Soil acidity and low soil fertility due to nutrient leaching coupled with low inorganic fertilizer usage is a major cause of low crop yields across Southwest Ethiopia. Recently, biochar potential to improve soil fertility has gained significant attention but there are limited studies on the use of biochar in combination with inorganic fertilizers. A field experiment was, therefore, conducted to investigate the effect of combined application of biochar and inorganic NP nutrient on soil physicochemical properties, growth and yield of potato in Andiracha district, Southwestern Ethiopia. The experiment was laid out in randomized complete block design (RCBD) and replicated three times. The treatment consisted of four levels of biochar rates (0, 2.5, 5 and 7.5 t ha−1) and four fertilizer rates of (0, 75,100 and 125% of recommended N P rates). Data were analyzed using SAS version 9.3 Software. Analysis of variance showed that combined application of biochar and inorganic NP fertilizer had highly significant (p < 0.01) effect on days to flowering, stem number, plant height, total leaf area, total dry biomass, marketable tuber number per hill and harvest index and significant (p < 0.05) effect on marketable tuber weight and total tuber weight ha−1. Combined application of 7.5 ton ha−1 biochar with 165 kg N and 60 kg P ha−1 resulted highest tuber yield (42.64 t ha−1), that increased yield by 28.99% compared with recommended NP fertilizer alone (165 kg N ha−1 and 60 kg P ha−1), and by 76.6% compared to the control. The increase was mainly attributed to the improvement in soil physico-chemical properties especially soil pH, CEC, organic matter, total N and available P which is a reflection of increase in soil fertility. Consequently, it was determined that the best course of action for potato production in the area was to apply 7.5 tons of biochar ha−1 together with 165 kg N and 60 kg P ha−1. Therefore, the study recommends adoption of low cost biochar production techniques and capacity building to ensure satisfactory knowledge of biochar use and its adoption by potato growers for soil fertility management and enhanced crop productivity.

Straw residue incorporation and potassium fertilization enhances soil aggregate stability by altering soil content of iron oxide and organic carbon in a rice–rape cropping system

AbstractBoth iron (Fe) oxide and soil organic carbon (SOC) content, among other factors, drive the development and subsequent stability of soil aggregates. However, the mechanism of these drivers in paddy‐upland rotation systems with straw residue incorporation is not well understood. In this multiyear (2011–2017) trial, we sought to study the factors which drive the stability of soil aggregates in such a rice‐rape (RR) agronomic system. In order to examine the effect of straw residue incorporation and potassium fertilization on soil aggregation dynamics, we divided our trial into four treatments: inorganic phosphorus (P) and nitrogen (N) fertilizer; inorganic NPK fertilizer; inorganic NP fertilizer plus straw residue; and inorganic NPK fertilizer plus straw residue. Treatments which incorporated straw residue significantly increased both the geometric mean diameter (GMD) and the mean weight diameter (MWD) of soil aggregates. Soil aggregate stability was greater after rape harvest than after rice harvest, while SOC shows the opposite trend. Straw residue incorporation increased the SOC and, specifically, concentrations of aliphatic‐C and aromatic‐C, particularly in aggregates greater than 0.25 mm. Straw residue addition significantly increased both the amorphous (Feo) and complex iron oxide (Fep) contents of soil. In both bulk soil and in aggregates greater than 5 mm, SOC and Fep were positively correlated with MWD, while in aggregates less than 5 mm, Feo was positively correlated with MWD. Overall, we suggest that the increased concentrations of SOC, alkane‐C, Feo, and Fep in soils after incorporation of straw residue were responsible for increasing soil aggregate stability.

Effect of high soil C/N ratio and nitrogen limitation caused by the long-term combined organic-inorganic fertilization on the soil microbial community structure and its dominated SOC decomposition

The application of organic fertilizers, such as straw and manure, is an efficient approach to maintain soil productivity. However, the effect of these organic fertilizers on soil microbial nutrient balance has not yet been established. In this study, the effects of the long-term combined organic-inorganic fertilization on microbial community were investigated by conducting a 30-year-long field test. Overall, the following five fertilizer groups were employed: inorganic NP fertilizer (NP), inorganic NK fertilizer (NK), inorganic NPK fertilizer (NPK), NPK + manure (MNPK), and NPK + straw (SNPK). The results indicated that the mean natural logarithm of the soil C:N:P acquisition enzyme ratio was 1.04:1.11:1.00 under organic-inorganic treatments, which showed a deviation from its overall mean ratio of 1:1:1. This indicates that microbial resources do not have a balance. Vector analysis (vector angle <45°) and threshold elemental ratio analysis (RC:N-TERC:N > 0) further demonstrated that the microbial metabolism was limited by Nitrogen (N) under SNPK and MNPK treatments. N limitation further influenced soil microbial community structure and its dominated SOC decomposition. Specifically, Microbial communities transformed into a more oligotrophic-dominant condition (fungal, Acidobacteria, Chloroflexi) from copiotrophic-dominant (Proteobacteria, Actinobacteria) condition with increasing N limitation. Lysobacter genus and Blastocatellaceae family, in the bacterial communities along with the Mortierella elongata species in fungal communities, were markedly associated with the N limitation, which could be the critical biomarker that represented N limitation. Both correlation analysis and partial least squares path modeling showed significant positive effects of N limitation on the ratio of bacterial functional genes (Cellulase/Amylase), involved in recalcitrant SOC degradation.

Nitrogen and phosphorus release from paper mill biosolids as affected by material source and soil type under controlled incubation

Combined paper mill biosolids (PB) are a well-known fertilizing source of nitrogen (N) and phosphorus (P). Many jurisdictions have established default values for estimating their agronomic N and P contribution, but nutrient release can vary with their chemical properties, and this has been little studied. The objective of this incubation study was to compare four PB of different sources along with a de-inking paper sludge (DPS) for their N and P release in three contrasting soils under controlled conditions (25 °C, 60% water-filled pore space). Treatments consisted of PB or DPS at 50 Mg fresh mass ha−1, PB at 30 Mg fresh mass ha−1 plus inorganic N to supply 100 kg available N ha−1, inorganic NP fertilizer, and an unfertilized control. Measurements of NO3 + NH4-N were made after 3 d and 1, 2, 3, 4, 6, 8, 12, and 16 wk of incubation. Mehlich-3 P was measured after 2 and 16 wk of incubation. Nitrogen mineralization generally declined a few days after PB addition and then gradually and constantly increased. The P mineralization of PB also increased with time. By the end of incubation, net N and P release averaged 30% (7%–49%) and 75% (16%–116%) of the NP fertilizer, respectively. The intensity of release, however, varied with material characteristics and soil type. Mineral N addition to the 30 Mg PB ha−1 promoted N release to a level comparable to NP fertilizer. Soil N immobilization occurred with the DPS application. Current default N value used for PB in Quebec and Ontario is appropriate but not P.

Effect of Integrated Farmyard Manure and NP Fertilizers Use on Hybrid Maize Yield and Soil Properties in Western Ethiopia

A study was carried out to assess the effect of integrated Farmyard Manure (FYM) and inorganic NP fertilizers use on yield and soil properties in Bako-Tibe district of Oromia, western Ethiopia. Five treatments (i.e., 110 kg N ha-1 + 46 kg P2O5 ha-1 (T1), 12 ton FYM ha-1 (T2) , 55 kg N ha-1 + 23 kg P2O5 ha-1 + 6 ton FYM ha-1(T3), 27.5kg N ha-1 + 11.5 kg P2O5 ha-1 + 6 ton FYM ha-1(T4) and the control (T5)) were used in a Randomized Complete Block Design (RCBD) with five replications using five farmers’ fields. Yield and yield related parameters were analyzed using SAS statistical software version 9.0. Economic analysis was performed to compare treatments advantages. The treatment with half the recommended NP (55 kg N ha-1 + 23 kg P2O5 ha-1 + 6 ton FYM ha-1) showed superior plant growth performance as compared to other treatments. Pure use of inorganic NP resulted in high Na, K, Ca and P composition of grain while pure FYM use resulted in high content of Mg and Ca composition. The level of P in grain decreased with the increasing of FYM. Soil fertility parameters considered showed no significance difference (P: 0.05) among the treatments. The mean difference values indicated that use of pure inorganic fertilizer increased soil PH, exchangeable Na, and available S. Use of pure farmyard manure resulted in an increase in the soil exchangeable Na, K, Mg, total Nitrogen, and available K and S. The use of half of the recommended inorganic fertilizer and FYM can enhance soil fertility in addition to yield improvement.&#x0D;

Effect of Jatropha curcas L. Press-cake and Inorganic NP Fertilizers on the Productivity of Potato (Solanum tuberosum L.) and Soil Properties

Low soil fertility is a major constraint to potato production in Ethiopia. A field experiment was conducted at rare research farm, main campus of HU in Ethiopia, during the main growing season of 2011 under supplementary irrigation to evaluate the effects of J. curcas L. press-cake and inorganic NP fertilizers on the productivity of potato (S. tuberosum L.) and soil properties. The treatments consisted of four rates of J. press-cake (0, 2, 4 and 6 t ha-1) and 5 rates of combined mineral NP (0 + 0; 0 + 46; 50 + 0; 50 + 46; 100 + 92 kg N + P, respectively, ha-1) fertilizers. The experiment was laid out as a RCBD in a factorial arrangement and replicated three times. The plot sizes were 3.75 m x 3.9 m. The distance between plots and blocks was maintained at 1 and 2 m, respectively. All agronomic and soil data were collected and analysis of variance was done. The results indicated that J. Press-cake along with mineral fertilizer significantly enhanced potato tuber yields and soil OM. From the results of the study, it could be deduced that 2 t J. press.-cake ha-1 resulted in an optimum total tuber yield.

Effect of Jatropha curcas L. Press-cake and Inorganic NP Fertilizers on the Productivity of Potato (Solanum tuberosum L.) and Soil Properties

Low soil fertility is a major constraint to potato production in Ethiopia. A field experiment was conducted at rare research farm, main campus of HU in Ethiopia, during the main growing season of 2011 under supplementary irrigation to evaluate the effects of J. curcas L. press-cake and inorganic NP fertilizers on the productivity of potato (S. tuberosum L.) and soil properties. The treatments consisted of four rates of J. press-cake (0, 2, 4 and 6 t ha-1) and 5 rates of combined mineral NP (0 + 0; 0 + 46; 50 + 0; 50 + 46; 100 + 92 kg N + P, respectively, ha-1) fertilizers. The experiment was laid out as a RCBD in a factorial arrangement and replicated three times. The plot sizes were 3.75 m x 3.9 m. The distance between plots and blocks was maintained at 1 and 2 m, respectively. All agronomic and soil data were collected and analysis of variance was done. The results indicated that J. Press-cake along with mineral fertilizer significantly enhanced potato tuber yields and soil OM. From the results of the study, it could be deduced that 2 t J. press.-cake ha-1 resulted in an optimum total tuber yield.

Determination of Inorganic N and P Fertilizers on Fruit Yield and Yield Components of Pineapple (Annanas comosus MERR L. Var. Smooth cayanne) at Gojeb, South Ethiopia

The study was conducted at Gojeb Horizan plantation farm of South Ethiopia, for two cropping seasons (20122014 and 2015–2017 as a ratoon crop). The aim of the study was to determine the appropriate inorganic NP fertilizer amount required for high yield and quality of pineapple (variety Smooth cayenne) for production. Four levels of N (0, 93.6, 108 and 281 kg ha-1) and four levels of P (0, 134.8, 269.6 and 404.4 kg P2O5 ha-1) weresourced from Urea and DAP arranged in RCBD with three replications. Different yield, quality and yield related traits collected and subjected to data analysis. The result revealed that, the highest fruit yield obtained from application rate of 281 kg N ha-1 and 134.8 kg P2O5 ha-1. The rate of application of nitrogen of 281 kg ha-1 significantly increased the fresh fruit yield of pineapple up to 26.86% than the control. Likewise, application of phosphorus rate of 134.8 kg P2O5 ha-1 increased the fresh fruit yield of pineapple by 8.93% than the control. Similarly, the quality (TSS content) of pineapple significantly decreased when the applied nitrogen beyond 93.6 kg N ha-1 rate. Apply treatments beyond 93.6 kg N ha-1, similarly, the quality (TSS content) declined by 5.67%. The economic analysis also revealed that the highest net benefit of 18305.0 Ethiopian Birr/ha (ETB/ha) with marginal rate of return of 705.4% was obtained by the application of 281 kg N ha−1. Likewise, the net benefit of 131774.0 ETB/ha with marginal rate of return of 5431.74% were obtained by the application of 134.8 kg P2O5 ha−1. Based on the above results, a combined application of 281 kg N ha−1 and 134.8 kg P2O5 ha−1 are optimum and economically better for pineapple production at Gojeb plantation and its surroundings.

Evaluation of Planting Date and Different Inorganic NP Fertilizer Rates for Irish Potato (&amp;lt;i&amp;gt;Solanum tuberosum L.&amp;lt;/i&amp;gt;) Production at Bore, Southern Ethiopia

The experiment was conducted at Bore Agricultural Research Center on station for three consecutive years’ main cropping seasons with the aim to adjust planting date and fertilizer rate for Irish Potato production. Four level of fertilizer rate (0, 61.5, 82, and 114 kg Nitrogen and 0, 69, 92, and 115kg P ha^-1 and planting date Immediately rain season (T1), 7days after rain (T2), 15days after rain (T3), 3 weeks later (T4). The treatments were arranged in RCBD in factorial arrangement with 3 replications. Tubers were planted on plot size of 4 m x 5m at spacing of 1m between plot, 1.5m b/n block, 70 cm between rows and 30cm between plants. The variety used in this experiment was Gudane. Based on the combined analysis of variance treatments over three consecutive years indicated that interaction effect of Planting Date and Different Fertilizer Rate significantly (P<0.001) affected Days to 50% emergency, maturity, plant height, stem number, number of tubers, and fresh tuber yield. However, parameters days to flowering and average tuber weight are non-significant (P<0.05) difference between each treatment means. The combined effect of immediate planting date (T1) with control (no nutrient) treatment (R1) recorded shortest (9.55 days) to emergency and early days to maturity (104.22days). And also regarding plant height the maximum (74.28 cm) plant height was recorded for treatment planted at first planting date with combined nutrient application of 114 kg N* 115 kg P. The interaction effect of immediate planting date with 82 kg N*92 kg P₂O₅ shows significant (P<0.05) maximum (9.1) stem number of potato. The maximum number of tubers (9.88, 9.66 and 9.44) was observed when tubers were planted at first week and applied with 82 kg N+92 kg P; 114kg N+115 kg P and second week with 82 kg N+92 kg P of fertilizer rates respectively. The highest Total tubers yield (41821 kg ha^-1 and 41395 kg ha^-1) were obtained from T₁R₃ (Immediate planting with combined nutrient of 82 kg N* 92 kg P₂O₅) and T₂R₃ (Immediate planting with combined nutrient of 82 kg N* 92 kg P₂O₅) respectively.

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The NP fertilizer or organic resources alone may not provide sufficient amounts or may be unsuitable for alleviating specific constraints to crop production. Therefore, a field experiment was conducted at Maitsebri Research Station of Shire-Maitsebri Agricultural Research Center (SMARC) to study the effect of inorganic NP fertilizers and vermicompost on growth, seed yield and yield components of red onion (Allium cepa L.) variety during 2016/17 dry season under irrigation. The treatments consisted of five NP fertilizer rates {0, 25, 50, 75 and 100% of recommended NP rates (69 kg N and 92 kg P2O5 ha-1)} and four rates of vermicompost (0, 2.5, 5.0, 7.5 t ha-1). The experiment was laid out in a factorial arrangement using randomized complete block design (RCBD) with three replications. Results of the analysis revealed that the interaction effects on inorganic NP fertilizer and vermicompost significantly (P<0.05) affected plant height. Days to bolting, days to 50% flowering, flower stalk diameter and days to maturity were significantly (P<0.05) affected by the main effect of NP fertilizer rates and vermicompost. Similarly, numbers of umbels per plant, umbel diameter, number of seeds per umbel and seed weight per umbel were significantly affected by the main effect of NP fertilizer rates and vermicompost. The highest seed yield per hectare (1462.5 kg ha-1) was obtained from the plants grown at 75% of RDF with vermicompost at 2.5 t ha-1 which was about 263% higher than seed yield from unfertilized control plot. It can, thus, be concluded that the combined application of 75% of RDF with vermicompost at 2.5 t ha-1can improve growth, seed yield and yield components of Bombay red onion variety in the study area. Key words: Growth, onion, NP fertilizers, parameters, seed yield, vermicompost.

The integrated use of excreta-based vermicompost and inorganic NP fertilizer on tomato (Solanum lycopersicum L.) fruit yield, quality and soil fertility

PurposeA field study was conducted at Dire Dawa, Eastern Ethiopia, with an objective to find out an optimum combination of inorganic (NP) fertilizer and excreta-based vermicompost for best economic yield and quality of tomato and to assess their effect on selected physico-chemical properties of amended soil after crop harvest.MethodsThe experiment consisted of eight treatments where the mineral (NP) fertilizer and the excreta-based vermicompost were combined in different proportions being arranged in a completely randomized block design replicated three times.ResultsGrowth, yield and quality attributes of tomato as well as the post-harvest soil nutrient status were markedly influenced by the nutrient treatments. The highest values for the various growth, yield and quality attributing parameters were recorded for the treatment combination consisting 75% of the recommended rate of NP fertilizer + 11.25 ton ha−1 vermicompost (T6), this treatment was also observed to have the highest net benefit with acceptable economic return as well as a fairly high residual soil nutrient status. Following this treatment, is the integration of 50% of recommended rate of NP fertilizer + 7.5 ton ha−1 vermicompost (T3) which surpassed the sole mineral fertilizer and vermicompost in terms of the crop’s yield and its economic return.Conclusion25–50% of the recommended rate of chemical fertilizer can be supplemented through vermicompost. However, in order to generate more reliable information, there is a need to conduct more such studies using more integration ratios of these nutrient sources (NP fertilizer and vermicompost) at various soil and agro-climatic conditions.

Growth, dry matter production of avocado (Persea americana Mill.) seedlings and soil physicochemical properties as affected by organic and inorganic nutrient sources

A lath house trial involving four doses of inorganic N and P and six types of organic potting materials was undertaken in the Jimma Agricultural Research Centre in the year 2011 to determine the effect of organic and inorganic nutrient sources on the soil physico-chemical properties, growth and dry matter production of avocado seedlings. Four levels of inorganic N and P (N 0 P 0 , N 150 P 200 ,N 300 P 400 and N 450 P 600 mg/pot) as the first factor and five organic materials, FYM (farmyard manure), FD (farmyard manure mixed with decomposed coffee husk), DCH (decomposed coffee husk), UCH (un decomposed coffee husk) and UF (un decomposed coffee husk mixed with farmyard manure), including TS (Top soil) as the second factor were evaluated in a Randomized Complete Block Design with three replications. Avocado shoot (plant height, stem girth, number of leaves and leaf area) and root growths (root girth, primary root length and lateral root length) were significantly (p TS:FD (2:1)>TS:DCH (2:1). Media prepared from TS:UCH(2:1)+N 0 P 0 and TS:DCH (2:1)+N 450 P 600 resulted significantly the lowest and the highest shoot dry mass, respectively. TS : FYM (2:1)+N 300 P 400 produced the highest total dry matter followed by TS:DCH (2:1)+N 450 P 600 . The lowest total dry matter, on the other hand, was obtained from TS:UCH (2:1) + N 0 P 0 . Decomposed organic materials incorporated into the growing media had significantly improved the water holding capacity of the media at both the permanent and field capacity. The decomposed organic materials, in particular, had a positive influence on most chemical properties considered during the study (Total N, available P, Organic carbon, pH, CEC and EC).With the increase in the rate of application of inorganic NP fertilizers, the pH and EC of the growing media had accordingly decreased; Total N and available P, on the other hand, had improved. Apart from independent effects, the electrical conductivity of the growing media was also significantly affected by the interaction of organic and inorganic source of fertilizers. In conclusion, most vigorous avocado seedlings under lath house condition was obtained by amelioration of the growth media using TS : FYM(2:1) +N 300 P 400 followed by TS: DCH (2:1) + N 450 P 600 .

Effects of Farmyard Manure and Inorganic Fertilizer Application on Soil Physico-Chemical Properties and Nutrient Balance in Rain-Fed Lowland Rice Ecosystem

A field experiment was conducted to assess the effects of combined application of farm yard manure (FYM) and inorganic NP fertilizers on soil physico-chemical properties and nutrient balance in a rain-fed lowland rice production system in Fogera plain, northwestern Ethiopia. The study was carried out during the main cropping seasons of 2010 and 2011. Twenty-seven treatments comprising a factorial combination of three rates of FYM (0, 7.5, and 15 t·ha-1), three rates of nitrogen (0, 60, 120 kg·N·ha-1) and three rates of phosphorus (0, 50 and 100 kg·P2O5·ha-1) were tested. The experiments were laid out as a randomized complete block design with three replications. Bulk density, organic matter content, and available water holding capacity, total N, and available P of the soil were measured just after harvesting the rice crop. Results showed that application of 15 t·FYM·ha-1 significantly increased soil organic matter and available water holding capacity but decreased the soil bulk density, creating a good soil condition for enhanced growth of the rice crop. Application of 15 tFYM·ha-1 increased the level of soil total nitrogen from 0.203% to 0.349%. Combined application of 15 t·ha-1·FYM and 100 kg·P2O5·ha-1 increased the available phosphorous from 11.9 ppm to 38.1 ppm. Positive balances of soil N and P resulted from combined application of FYM and inorganic N and P sources. Application of 15·t ha-1·FYM and 120 kg·N·ha-1resulted in 214.8 kg·ha-1·N positive balance while application of 15 t·ha-1·FYM and 100 kg·P2O5·ha-1 resulted in a positive balance of 69.3 kg·P2O5·ha-1 available P. From the results of this experiment, it could be concluded that combined application of FYM and inorganic N and P fertilizers improved the chemical and physical properties, which may lead to enhanced and sustainable production of rice in the study area.

Effect of integrated use of cattle manure and inorganic fertilizers on tuber yield of potato in Ethiopia

A field experiment was conducted to assess the effect of farmyard (cattle) manure (FYM) and inorganic nitrogen (N) phosphorus (P) fertilizers on growth and tuber yield of potato (Solanum tuberosum L.). The treatments consisted of factorial com- bination of 4 levels of FYM (0. 10, 20 and 30 t h -1 ) and three levels of inorganic NP fertilizers (0, 33.3%, 66.6% recommended rates) laid out in a Randomized Complete Block Design (RCBD) replicated three times. Results demonstrated that the applica- tion of 20 or 30 t ha -1 FYM + 66.6% of the recommended inorganic NP fertilizers significantly increased total tuber yield over the application of full dose of inor - ganic NP fertilizers without FYM in vertisol whereas in nitosol, the highest level of FYM (30 t ha -1 ) + 66.6% of the recommended inorganic NP fertilizers significantly improved total tuber yield over the application of full dose of inorganic NP fertil- izers without FYM. The application of 10 t ha -1 FYM + 66.6% of the recommended inorganic NP fertilizers and 20 or 30 t ha -1 FYM + 33.3% of the recommended inor- ganic NP fertilizers gave a total tuber yield, which was on par with the tuber yield obtained due to the application of full dose of inorganic NP fertilizer alone, in both soils. Thus, the application of 10 t ha -1 and 20 or 30 t ha -1 FYM resulted in a saving of 33.3% and 66.6% of the recommended NP fertilizers, respectively without sig- nificantly reducing the total tuber.

Soil properties related to the spatial pattern of microbial biomass and respiration in agroecosystems

Soil microorganisms exhibit a high degree of spatial variation, even in homogenously managed agroecosystems. The spatial pattern of microbial biomass and activity may be related to soil properties like hydrology, texture, organic matter and pH. This study took place in a 0.4-ha field with research plots under wheat and maize production. Soil microbial biomass, respiration and extractable nutrient levels were not generally affected by fertilizer treatments (inorganic NP fertilizer, poultry manure), relative to the unfertilized plots. This was probably due to soil heterogeneity; for instance, soil pH (1:2, soil:water) ranged from 5.8 to 7.2 across the field. Exploratory path analysis revealed that soil pH, dissolved organic carbon and total organic carbon concentrations were directly related to the spatial pattern in soil microbial biomass and respiration. This work demonstrates that path analysis could be used to identify independent soil variables and describe relationships between soil properties and microbial indicators in spatially heterogeneous agroecosystems. Key words: Field variability, microbial biomass, mineral fertilizer, organic amendment, soil respiration, spatial dependence

Inoculation of grass and tree seedlings used for reclaiming eroded areas in Iceland with mycorrhizal fungi

The objective of this study was to investigate the response of plant species used for reclamation of eroded areas in Iceland to inoculation with mycorrhizal fungi. In a greenhouse trial,Leymus arenarius andDeschampsia beringensis were grown in pots with volcanic ash collected from a site near the Mt. Hekla volcano in Iceland and were inoculated with arbuscular mycorrhizal fungi (AMF) isolatesGlomus mosseae BEG25 orGlomus intraradices BEG75. In two field experiments conducted on volcanic tephra fields near Mt. Hekla, a native soil inoculum or commercial inocula TerraVital-D and Terra Vital-G Ecto Mix were compared for efficacy onL. arenarius andBetula pubescens. After four months of growth, the presence of AMF in the pot experiment significantly increased the capacity of grass root systems to bind soil particles. In the field, inoculation significantly increased the number ofL. arenarius plants, which emerged from seed and their subsequent survival and growth. Seedlings ofB. pubescens grew best following inoculation with ectomycorrhizal fungal (ECMF) inoculum and a subsequent application of inorganic NP-fertilizer. The addition of native soil inoculum had almost no effect on growth of either grass or trees. Our results indicate that reclamation of eroded areas in Iceland could benefit from the use of a ppropriate mycorrhizal fungi, which might improve plant establishment and growth and increase soil aggregation and stability.