Effect of Application of Different Types of Organic Composts on Rice Growth under Laboratory Conditions

In the present study, pot experiments were conducted to evaluate the effects of the application of two different kinds of composts: pea-rice hull compost (PRC) and cattle dung-tea compost (CTC) on rice growth. These composts differed in their nitrogen composition, as well as in their effect on plant height, number of tillers, dry matter yield and nutrient uptake (nitrogen (N), phosphorus (P), potassium (K)) of rice plants. Plants were cultivated in 1/5,000 Wagner pots, which contained 3 kg of soil, completely mixed with the composts (PRC 404 g; CTC 380 g) and chemical fertilizer (CHEM), respectively in the first crop. The residual effect of the composts was studied after the plants of the first crop were harvested. All the treatments were replicated four times, with a randomized complete block design. The nutrient concentrations in the roots, leaf sheaths, leaf blades, stalks, and grain were analyzed at different growth stages. At the most active tillering and heading stages of the plants of the first crop, the number of tillers, dry matter yield and the amount of nutrients absorbed from the CHEM treatment were found to be higher than those in the other treatments. The values of the plant height, straw growth and nutrient uptake of the rice plants with the PRC treatment were the highest among all the treatments at the maturity stage. In the plants of the second crop, the values of the plant height, number of tillers, straw and whole plant yield and the N and K uptake from the PRC treatment were the highest among all the treatments at the heading and maturity stages. The chemical fertilizer was a fast-release fertilizer used to supply nutrients at the early stage of rice growth in the first crop. The beneficial effect of the composts on rice growth and nutrient uptake was conspicuous in the second crop, compared with that of routine treatment of chemical fertilizer.     

Effect of different composts on growth and nitrogen composition of Chinese mustard in an acid red soil

Abstract

A pot experiment was conducted to assess the effect of different kinds of composts on the growth and nitrogen (N) composition of Chinese mustard in acid red soil. There were six treatments including a lime‐chemical fertilizer treatment and a control plot of conventional chemical fertilizer. The plants were harvested 37 days after transplanting and the growth and N composition of these plants were measured. The soil was also sampled, and selected chemical properties were determined after harvesting the plants. The results show that different composts affected the growth and soil chemical properties significantly. The pH, nitrate nitrogen (NO₃‐N), ammonium N (NH₄‐N), electrical conductivity (EC), and 1 N ammonium acetate exchangeable potassium (K), calcium (Ca), magnesium (Mg), aluminum (Al), manganese (Mn), and iron (Fe) were all significantly affected by the compost treatment. The growth of plants in the control treatment was significantly lower than that of the compost‐treated and lime‐treated plants, suggesting that the acid Oxisol is unfavorable for the growth of Chinese mustard. Some composts could increase the growth of Chinese mustard. The lime‐treated plants had higher concentrations of chlorophyll a and chlorophyll b than those of the compost‐treated plants. There were no significant differences between treatments in the concentrations of chlorophyll a and chlorophyll b, however, there was a close correlation between the total chlorophyll concentrations and the shoot yield of the plants. The NO₃‐N, soluble reduced N, and insoluble N concentrations in leaf blades and petioles of Chinese mustard varied significantly according to the compost applied. The hog dung compost B could adequately supply nutrients especially N for plant growth and caused little NO₃‐N accumulation in plant tissues.     

The effect of winery solid waste compost application on maize growth,biomass yield,and nutrient content under greenhouse conditions

A greenhouse study was conducted to assess the fertilizer value and determine the optimum application rate of five winery solid waste (WSW) composts containing varied filter material (FM) mixed proportions with grape marc and pruning canes using maize. The composts comprised of 4, 10, 20, 30, and 40% FM (w/w) designated C4FM, C10FM, C20FM, C30FM, and C40FM, respectively. Application rates of 5, 10, 20, 40, and 80 t ha^?1 were used; while unamended control and inorganic NPK fertilizer treatments were included as references. The results showed that application of composts with 20% FM or more at 80 t ha^?1 significantly increased the dry matter yield more than NPK fertilizer but full potential was not reached due to inadequate nitrogen supply. Maize shoot K content from compost treatments exceeded the critical nutrient level while the shoot Zn content from compost treatments with 20% FM or less also exceeded the critical level. The results revealed that these composts could serve as potential good sources of K and Zn for maize production, particularly, in sandy soils where these nutrients are often reported to be deficient. Quantitative estimate of the optimum rate of the composts for dry matter production ranged from 75 to 307 t ha^?1.     

Effect of the long-term application of organic matter on soil carbon accumulation and GHG emissions from a rice paddy field in a cool-temperate region,Japan-II. Effect of different compost applications-

ABSTRACT

The influence of long-term application of different types of compost on rice grain yield, CH₄ and N₂O emissions, and soil carbon storage (0 ? 30 cm) in rice paddy fields was clarified. Two sets of paddy fields applied with rice straw compost or livestock manure compost mainly derived from cattle were used in this study. Each set comprised long-term application (LT) and corresponding control (CT) plots. The application rates for rice straw compost (42 years) and livestock manure compost (41 years in total with different application rates) were 20 Mg fresh weight ha^–1. Soil carbon storage increased by 33% and 37% with long-term application of rice straw compost and livestock manure compost, respectively. The soil carbon sequestration rate by the organic matter application was 23% higher with the livestock manure compost than with the rice straw compost. The rice grain yield in the LT plot was significantly higher than that in the corresponding CT plot with both types of compost. Although the difference was not significant in the rice straw compost, cumulative CH₄ emissions increased with long-term application of both composts. Increase rate of CH₄ emission with long-term application was higher in the livestock manure compost (99%) than that in the rice straw compost (26%). In both composts, the long-term application did not increase N₂O emission significantly. As with the rice straw compost, the increase in CH₄ emission with the long-term application of livestock manure compost exceeded the soil carbon sequestration rate, and the change in the net greenhouse gas (GHG) balance calculated by the difference between them was positive, indicating a net increase in the GHG emissions. The increase in CH₄ and net GHG emissions owing to the long-term application of the livestock manure compost could be higher than that of the rice straw compost owing to the amount of applied carbon, the quality of compost and the soil carbon accumulation. The possibility that carbon sequestration in the subsoil differs depending on the type of composts suggests the importance of including subsoil in the evaluation of soil carbon sequestration by long-term application of organic matter.     

Effects of phosphorus-based application of animal manure compost on the yield of silage corn and on soil phosphorus accumulation in an upland Andosol in Japan

Animal manure contains significant amounts of nitrogen (N) and phosphorus (P) that can be utilized as fertilizer. However, manure application rates are generally set to meet crop N demand, which results in excess P application which increases the risk of P loss into bodies of water. We examined the application method of manure compost based on crop P demand on the dry matter yield of silage corn (Zea mays L. var. indentata), on nutrient uptake and on soil P accumulation in an upland Andosol with a high P-fixing capacity. Cattle and poultry manure composts (CMC and PMC) with different P solubility were applied to meet the crop’s N requirements (N-based application) or P requirements (P-based application) in 3 consecutive years. Supplemental N was applied using polyolefin-coated urea in the P-based treatments. The dry matter yields and nutrient uptakes of silage corn in the P-based CMC and PMC application systems were similar to those in the corresponding N-based systems. The average relative efficiency of N in CMC (33%) was close to the predicted value (30%) during the study. On the other hand, the relative efficiency of N in PMC (42%) was higher than the predicted value (28%). The average relative efficiency of P from CMC and PMC was 109% and 50%, respectively. These were higher than the predicted values based on the available P proportion (the sum of water- and sodium bicarbonate-soluble P) for CMC (78%) and PMC (34%), indicating that the available P fraction in the manure composts was more effective than that in P fertilizer for corn growth or that the other P fractions were also effective for corn. P-based manure compost application lowered the soil P accumulation to between 41 and 43% of the value in the N-based accumulation (versus a value of between 31 and 40% of that value for soil Truog-P). Compared to N-based manure compost application, P-based manure compost application with supplemental N fertilizer produced similar dry matter yields of corn and suppressed soil P accumulation in the upland Andosol field.     

Ryegrass Response to Mineral Fertilization and Organic Amendment with Municipal Solid Waste Compost in Two Tropical Agricultural Soils of Mali

Abstract

A pot experiment was conducted to assess the effect of mineral fertilization and compost on the growth and chemical composition of ryegrass (Lolium perenne L.) grown on two Malian agricultural soils coming from Baguinéda, abbreviated as Bgda, (12°23′ S, 7°45′ W) and Gao (16°18′ N, 0°). Treatments included non‐fertilized control, NPK alone, NPK + C₂₅, NPK + C₅₀, NPK + C₁₀₀, PK + C₅₀, NK + C₅₀, NP + C₅₀, K + C₅₀, P + C₅₀, N + C₅₀, and C₅₀ alone, where NPK represents the non modified Hoagland's solution and C₂₅, C₅₀, and C₁₀₀ represent the different rates (25, 50, and 100 T/ha) of compost. Compost and mineral fertilization significantly increased dry matter production. The application of 50 T/ha of compost alone increased the dry matter yield by 10 and 17.5% while mineral nitrogen–phosphorus–potassium (NPK) increased yield by 69.7 and 65% for Gao and Bgda, respectively. The combination of compost and mineral NPK (NPK + C₂₅ for Gao and NPK + C₅₀ for Bgda) affected the highest dry matter yield. For both soils, N concentrations in plants increased significantly with compost rate. Phosphorus and K concentrations in plants varied according to the soil. The application of compost increased the uptake of iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), and potassium (K from both soils). Increases in soil organic carbon, available P, calcium (Ca), magnesium (Mg), Fe, Mn, Zn, Cu, K, and pH were observed in treatments receiving compost. Therefore, compost appeared to be a good supplier of nutrients for tropical soils.     

Comparisons of Composts with Low or High Nutrient Status for Growth of Plants in Containers

Abstract

Composts may be incorporated into container mixes for several purposes, including to supply nutrients, add organic matter, or suppress plant diseases. The objective of this research was to assess the nutritional benefits of two composts derived in common from composted chicken manure and used in formulation of container media for growth of tomato (Lycopersicon esculentum Mill.). The composts differed in extractable and total plant nutrients so that one of the composts was considered a nutrient‐rich material and the other a nutrient‐poor material. Media were formulated from soil or peat with the composts added in a progressive array of concentrations from a medium with no compost addition to a medium that was all compost. Half of the media were treated with a water‐soluble, complete fertilizer and half were left unfertilized. Optimum growth occurred in media in which compost did not exceed 25% of the volume. The beneficial effects of the composts on plant growth were associated with increased supply of nutrients for the plants. The suppressive effects were attributed to restricted accumulation of nutrients with the nutrient‐poor compost and to excessive potassium supply and accumulation with the nutrient‐rich compost. Fertilization was beneficial in increasing plant growth with the nutrient‐rich compost and was essential for plant growth with the nutrient‐poor compost. The research demonstrated that composts can be used in formulation of media for container growth of plants.     

Integrated nutrient management for better quality and yield of Kinnow mandarin

This study was carried out to determine the integrated effect of organic matter alone and in combination with chemical fertilizers in order to maintain the nutritional status in Kinnow fruit plants. Lahore Compost was used as a source of organic matter. Treatments were made by using compost alone and in combination with nitrogen, phosphorus, potassium (NPK), and well-rotten farm yard manure (FYM; cow dung). Treatments were applied before flowering and after fruit set. Effect of these treatments on different physicochemical characteristics of Kinnow fruit and nutritional status in tree leaves was determined. Among all treatments, minimum flower drop, maximum yield, and better fruit quality were recorded in plants where 40 kg compost + 1/2 recommended doses of NPK were applied before flowering and after fruit setting, while minimum fruit set was recorded from the plants where 30 kg compost alone was applied before flowering.     

Comparative Effectiveness of Organic-Based Fertilizer To Mineral Fertilizer on Tomato Growth and Fruit Yield

The effect of three different organic based fertilizers (OBF) was compared to conventional chemical fertilizer on tomato (Lycopersicon esculentum). The OBF is composted plant material fortified with poultry manure. The compost used was made from Maize (MP), guinea grass (GP) and cowpea (CP) stovers in combination with poultry manure in ratio 3:1 by weight. Two rates of each compost type (4t/ha, and 2t/ha + 30kgN/ha), the recommended rate of mineral fertilizer (i.e. 60kg N/ha) and nonfertilizer control plants constituted the treatments. Chemical analysis of the matured composts showed that CP compost produced the highest N while MP compost gave the best P, K, Ca and Mg. Compost type significantly influenced growth and yield characteristics with MP compost either at 4t/ha or 2t/ha + 30kgNha consistently producing the best results with significantly higher marketable fruit yield than the nonfertilized plants. The OBF was highly effective on crop performance and was favorably comparable with the chemical fertilizer. Irrespective of the compost type, OBF significantly increased dry matter and fresh fruit yield by 29.6% and 36.3% respectively and was well compared with applying 60kgN/ha in form of chemical fertilizer. Hence, the idea of OBF is a worthwhile venture in boosting agricultural production in Nigeria.     

Rice yield nutrient uptake as affected by cyanobacteria soil amendments—a pot experiment

Rice production and cyanobacterial N in acid soil can be improved by liming. There is evidence that the organic amendments can increase the soil pH. The aim of this study was to find appropriate combination of soil amendments and cyanobacteria capable for enhancing nutrient uptake and improving rice yield in acidic paddy soil. Three soil amendments (rice straw, sewage‐sludge composts, NPK) with and without inoculation of cyanobacteria were studied for rice plants (Oryza sativa L.) in a pot experiment. The sludge compost had significantly reduced soil acidity from 5.44 to 6.67. The plant N and K uptake increased significantly with sludge and cyanobacteria application. The yield components increased significantly with sludge, but decreased thereafter, an exception was the number of panicles, with straw compost. These characters were also significantly affected by inoculation with cyanobacteria except 100‐grain weight, filled‐grain percentage, and harvest index. The combination of sludge compost and cyanobacteria improved the yield components and consequently grain yield (138 g pot^–1) compared with sludge treatment only (132 g pot^–1). The amount of cyanobacterial N absorbed (N‐difference method) by rice plant under sludge compost was higher than that of soils amended with either rice straw or NPK treatments. Therefore, the addition of sewage sludge to acid paddy soil not only amended the soil properties but also activated the cyanobacteria and consequently improved rice plant nutrition and grain yield.     

Soil nutrient status and yield of rice as affected by long-term integrated use of organic and inorganic fertilizers

Nutrient balance is the key component to increase crop yields. Excess and imbalanced use of nutrients has caused nutrient mining from the soil and deteriorated crop productivity and ultimately soil health. Replenishment of these nutrients has a direct impact on soil health and crop productivity. Based on this fact, the present research was conducted to determine the effects of long-term integrated use of organic and inorganic fertilizers on soil nutrient status and yield (grain and straw) in rice. Different combinations of inorganic nitrogen (N) and organic sources (sewage sludge and compost) were applied to the soil. Data revealed that application of mineral NPK in combination with 50% N through compost significantly increased the organic matter content (0.36%), available phosphorus (16.50 kg/ha) and available potassium content (239.80 kg/ha) in soil. The maximum available N (225.12 kg/ha) was found by the substitution of 50% N through sewage sludge. This improvement in soil nutrient status through combined use of organic and inorganic fertilizers produced significant increase in grain and straw yield as compared to inorganic fertilizers alone. Maximum grain (6.96 t/ha) and straw (8.56 t/ha) yields were found in treatment having substitution of 50% N (recommended) through compost @10t/ha. Also, a significant positive correlation was found between soil nutrients and straw and grain yield in rice. Thus the study demonstrated that substitution of 50% inorganic N through compost will be a good alternative for improving soil fertility.     

Application rate and composting method affect the immediate and residual manure fertilizer value in a maize–rice–rice–maize cropping sequence on a degraded soil in northern Vietnam

A field experiment was carried out in northern Vietnam to investigate the effects of adding different additives [rice (Oriza sativa L.) straw only, or rice straw with added lime, superphosphate (SSP), urea or a mixture of selected microorganism species] on nitrogen (N) losses and nutrient concentrations in manure composts. The composts and fresh manure were applied to a three-crop per year sequence (maize–rice–rice) on a degraded soil (Plinthic Acrisol/Plinthaquult) to investigate the effects of manure type on crop yield, N uptake and fertilizer value. Total N losses during composting with SSP were 20% of initial total N, while with other additives they were 30–35%. With SSP as a compost additive, 65–85% of the initial ammonium-N (NH₄-N) in the manure remained in the compost compared with 25% for microorganisms and 30% for lime. Nitrogen uptake efficiency (NUE) of fresh manure was lower than that of composted manure when applied to maize (Zea mays L.), but higher when applied to rice (Oriza sativa L.). The NUE of compost with SSP was generally higher than that of compost with straw only and lime. The mineral fertilizer equivalent (MFE) of manure types for maize decreased in the order: manure composted with SSP?>?manure composted with straw only and fresh manure?>?manure composted with lime. For rice, the corresponding order was: fresh manure?>?manure composted with SSP/microorganisms/urea?>?manure composted with lime/with straw alone. The MFE was higher when 5 tons manure ha^?1 were applied than when 10 tons manure ha^?1 were applied throughout the crop sequence. The residual effect of composted manures (determined in a fourth crop, with no manure applied) was generally 50% higher than that of fresh manure after one year of manure and compost application. Thus, addition of SSP during composting improved the field fertilizer value of composted pig manure the most.     

Effects of Different Organic Materials on Crop Production under a Rice–Corn Cropping Sequence

Soil organic matter (SOM) is an important index of soil quality because of its relationship with crop yield. The application of organic matter to soil is a significant method for increasing SOM. Different organic materials have varying effects in increasing SOM. This study investigates the effects of combining different sources of organic matter (i.e., compost, leguminous green manure, and peat) with a chemical nitrogen (N) fertilizer on the growth and N accumulation in corn and rice plants. This study examines seven treatments, including a no-fertilization check and a conventional chemical fertilizer treatment. Shoots of corn and rice were sampled at the tasseling (panicle initiation for rice) and maturity stages. The biomass yield was measured and the total N was analyzed. At the maturity stage, the soil samples were collected to determine the chemical properties. The results showed that a small percentage of the N in the compost and peat, after their application, was available to the crop during the growth season; the production of biomass and N absorption among rice and corn plants was minimal compared to that treated with chemical N fertilizer. The application of compost and peat resulted in SOM accumulation, particularly with peat. However, the application of compost combined with chemical fertilizer not only produced sufficient nutrients for crop growth but also resulted in an accumulation of SOM, which is vital for enhancing the soil quality. Most of the N in green manure (GM) was mineralized shortly after application, causing excessive growth of rice and corn plants during the early stage, but reducing their reproductive growth and grain yield.     

Growth of Date Palm (Phoenix dactylifera L.) in Composts of Olive Oil Mill Waste with Organic Household Refuse

This study highlights the effects of composts of olive mill wastes and organic household refuse with a pH range of 7 to 7.98 and a C/N ratio between 14.9 and 22, to improve the growth and the mineral nutrition of the date palm (Phoenix dactylifera L.). After 7 months of cultivation, plants amended with composts showed higher biomass production than the controls. Compost C1, i.e., the basic compost with no additives phosphate, at 100% and 45% doubled the production of dry matter in comparison with control plants. The rise of root biomass was considerably greater for plants grown with compost C1 without phosphate. In contrast, the shoot biomass was highly significant for composts C2 and C3 enriched with phosphate. The control plants, grown without amendment, showed significantly higher specific root length (SRL) and specific leaf length (SLL). The efficiency of compost application was reflected by the biomass rise, the number of emerged leaves (2.6–4), and the rise in leaf area (3.3 to 6.7 cm²) by improving the mineral nutrition of the date palm. The composts of olive mill waste and organic household refuse supplemented with natural rock phosphate, or not, generated a notable agronomic added value.     

Short‐term effects of in‐row subsoiling and simultaneous admixing of organic material on growth of spring barley (H. vulgare)

Previous studies have shown that deep tillage, so‐called subsoiling, is beneficial for yield development, and that tillage of deeper soil layers can promote water and nutrient availability during dry periods. The application of composts to the topsoil has been widely studied and evaluated, and it has been shown to improve soil stability and plant N uptake. These effects can differ over time depending on the compost type. Since dry periods have become more frequent, sustainable soil tillage and fertilizer practices must be developed. A combination of deep soil tillage and compost application might be a way to ensure proper plant supply during dry periods. Therefore, a field experiment on spring barley growth was carried out to evaluate the short‐term effects of in‐row subsoiling with simultaneous admixing of compost. Two types of composts and one organic fertilizer (Bio: decomposed organic waste, Green: decomposed green cuttings and CM: cattle manure) were admixed into the subsoil, and a control treatment received single deep loosening (DL) to a depth of 0.6 m. Yield development, yield parameters and grain quality were analysed and showed that the DL and Bio treatments resulted in the highest yields, and a significantly increased ear density and number of kernels. The TKW (100‐kernel weight) of the CM treatment was significantly lower than the other treatments. In all treatments, a clear trend of decreasing yields with increasing distance from the subsoil tillage was observed. Thus a subsoil tillage every meter can increase overall yield development and offers a new perspective for sustainable crop production.     

PHOSPHORUS UPTAKE AND USE EFFICIENCY IN FIELD CROPS

Phosphorus (P) is required by crop plants for many physiological and biochemical functions. Knowledge of phosphorus uptake and its use by crop plants is essential for adequate management of this essential nutrient. A field experiment was conducted during four consecutive years to determine P uptake and use efficiency by upland rice, dry bean, corn and soybean grown in rotation on a Brazilian Oxisol. Plant samples were taken at different growth stages during the growth cycle of each crop for phosphorus analysis. Phosphorus concentration (content per unit dry matter) significantly decreased in a quadratic fashion with the advancement of plant age in four crop species. Phosphorus concentration was higher in legumes compared to cereals. Phosphorus uptake in shoot, however, significantly increased in an exponential quadratic fashion with the advancement of plant age of crop species. At harvest, P uptake was higher in grain compared to shoot, indicating importance of this element in improving crop yields. Phosphorus use efficiency (grain or straw yield per unit P uptake) was higher in cereals compared to legumes. The P use efficiency for grain production was 465 kg kg^?1 for upland rice, 492 kg kg^?1 for corn, 229 kg kg^?1 for dry bean and 280 kg kg^?1 for soybean. The higher P use efficiency in cereals was associated with higher yield of cereals compared to legume species.     

Nutrient transformations in soil amended with rock phosphate enriched composts for improving productivity of wheat-green gram sequence

The present study focuses on the transformations of nitrogen (N), phosphorus (P), and sulfur (S) in soil amended with rock phosphate (RP) enriched composts prepared using different crop residues under wheat-green gram sequence. Data emanated from the field study revealed that significant buildup in available pools of potassium permanganate (KMnO₄-N), Olsen-P, and calcium chloride (CaCl₂-S) as well as different fractions of N, P, and S were maintained higher under RP enriched composts treated plot than control. The total N, P, and S varied from 979 to 1776, 604 to 1165, and 273 to 464 kg ha^?1, respectively in different treatments. The yield of wheat and green gram was significantly correlated with different fractions of N, P, and S in soil. Results conclude that RP enriched compost could be an alternative and cost-effective option for mitigating the shortage of chemical fertilizers for crop production.     

Effects of Composted Pulp and Paper Industry Wastewater Treatment Residuals on Soil Properties And Cereal Yield

The aim of this study was to investigate effects of pulp and paper industry wastewater treatment sludge composts on soil and cereal crops. Five forest industry wastewater sludge composts were tested in a field study which was conducted in a silty clay soil in southern Finland with barley in 1998, with oats in 1999 and with barley in 2000. Two composts contained only pulp mill biosludge and bark in a ratio of 1:4 and 1:2, respectively. Two other composts were mixtures of biosludge and primary sludge with the addition of bark in a ratio of 1:2 and 3:4, respectively. These two wastewater sludges originated from a pulp mill and from a recycled paper mill. The fifth compost consisted of biosludge and primary sludge from a board mill. Two application rates of each compost were studied: the low rate was based on an annual P fertilization rate recommended for barley, 50-200 m³/ha; and the high rate was a double or triple the low rate depending on the mineral N concentration of the compost, 150-600 m³/ha. Based on the Finnish fertilizer recommendations, nutrient demands of the test plants were annually fulfilled by mineral fertilizers depending on the treatment. Total contents of N, P, K and Ca in composts were 8.8-17.5, 0.7-3.9, 1.5-6.5, and 4-25 g/kg dry matter, respectively. Especially at high doses, composts had beneficial effects on soil bulk density, porosity, C and N contents and C:N ratio. Despite the high total N rates applied with the composts, the mineralization following crop harvest did not significantly increase soil nitrate late autumn or following spring as compared to the soils that received mineral fertilization. There was no significant difference in the grain yields between plots that received mineral fertilization and compost treatments supplemented with mineral fertilizers. However, there was a decreased fertilization effect of some composts on straw yields during the first experimental year, indicating immobilization of mineral N. Heavy metals added in soil with the composts did not significantly increase their concentrations in the grain crops. All the composts had relatively low nutrient contents and low fertilizing value, but beneficial effects on soil properties and were regarded as soil conditioners. Soil improving and fertilizing effects of the composts varied annually depending on the weather conditions during the growing season. Heavy metal concentrations of the composts studied were far below the limit values set for the soil conditioners in the Finnish government regulations.     

Yields and Nutrient Budgets Under Composts,Raw Dairy Manure and Mineral Fertilizer

Composts made from rural and urban residues are increasingly available. Farmers wishing to use these materials need to know how they will perform as crop nutrient sources. The objectives of this field experiment were to evaluate compost as an N source, and to track the effects of compost application on NPK budgets. Four composts of various feedstocks, maturity, and nutrient content were compared to raw dairy manure (RDM) and conventional mineral fertilizer (CNV). A 3-year rotation of corn (Zea mays L.), bell pepper (Capsicum annum), and small grain was established, with all crops present every year. Treatments were applied on an N-equivalent basis, using a 40% availability factor for compost and 50% for RDM. Yields from compost-amended corn were comparable to RDM and CNV by the second year. Pepper, a less N-demanding crop, had no significant yield differences among treatments for the three years. The manure-based compost treatments had the highest P and K surplus after three years, showing that loading levels of these nutrients need consideration when using compost to satisfy crop N needs. Rotations can be designed to extract more P and K, but more practical for the long-term would be reducing compost additions and substituting an additional N source such as a legume.     

Soil Physical Properties and Organic Matter Fractions Under Forages Receiving Composts,Manure or Fertilizer

A field study was conducted to assess the benefits, with respect to soil physical properties and soil organic matter fractions of utilizing composts from a diversity of sources in perennial forage production. A mixed forage (timothy-red clover (Trifolium pratense L.) and monocrop timothy (Phleum pratense L.) sward were fertilized annually with ammonium nitrate (AN) at up to 150kg and 300 N ha^?1 yr^?1, respectively, from 1998-2001. Organic amendments, applied at up to 600 kg N ha^?1 yr^?1 in the first two years only, included composts derived from crop residue (CSC), dairy manure (DMC) or sewage sludge (SSLC), plus liquid dairy manure (DM), and supplied C to soil at 4.6 and 9.2 (CSC), 10.9 (SSLC), 10.0 (DMC) 2.9 (DM) Mg C ha^?1. Soil samples (0-5cm; 5-10cm;10-15cm) were recovered in 2000 and 2001. Improvements in soil physical properties (soil bulk density and water content) were obtained for compost treatments alone. Composts alone influenced soil C:N ratio and substantially increased soil organic carbon (SOC) concentration and mass (+ 5.2 to + 9.7 Mg C ha^?1). Gains in SOC with AN of 2.7 Mg C ha^?1 were detectable by the third crop production year (2001). The lower C inputs, and more labile C, supplied by manure (DM) was reflected in reduced SOC gains (+ 2.5 Mg C ha^?1) compared to composts. The distribution of C in densiometric (light fraction, LF; >1.7 g cm^?3) and particulate organic matter (POM; litter (>2000μm); coarse-sand (250-2000μm); fine-sand (53-250μm) fractions varied with compost and combining fractionation by size and density improved interpretation of compost dynamics in soil. Combined POM accounted for 82.6% of SOC gains with composts. Estimated compost turnover rates (k) ranged from 0.06 (CSC) to 0.09 yr^?1 (DMC). Composts alone increased soil microbial biomass carbon (SMB-C) concentration (μg C g^?1 soil). Soil available C (C_ext) decreased significantly as compost maturity increased. For some composts (CSC), timothy yields matched those obtained with AN, and SOC gains were derived from both applied-C and increased crop residue-C returns to soil. A trend towards improved C returns across all treatments was apparent for the mixed crop. Matching composts of varying quality with the appropriate (legume/nonlegume) target crop will be critical to promoting soil C gains from compost use.