Leaf and root litter of a legume tree as nitrogen sources for cacaos with different root colonisation by arbuscular mycorrhizae

Traditionally cacao (Theobroma cacao L.) is cultivated under legume shade trees, which produce N-rich litter that improves soil organic matter content, microbial activity, and recycles N to the crop. Arbuscular mycorrhiza forming fungi (AMF) are known to play an important role in plant nutrient uptake, yet their role in plant N uptake from organic residues in tropical agroforestry systems is not clear. We studied root and leaf litter of the legume shade tree Inga edulis Mart. as a source of N for cacao and the importance of AMF colonisation in the uptake of litter N under controlled conditions. Leaf and root litter of I. edulis enriched with ¹⁵N was added to cacao pots filled with field soil. Half of the cacao saplings were AMF-inoculated and the soil of non-inoculated saplings was treated with fungicide to suppress AMF. During the 10-week experiment, young cacao leaves were sampled for ¹⁵N analyses and at the end of the experiment whole plants were harvested. Microbial populations in the soil were determined using phospholipid fatty acid (PLFA) analysis, and AMF structures in the roots were quantified. Fungicide treatment decreased AMF structures in roots and increased bacterial populations, but did not affect the decomposition rate of either litter type. Inoculated and non-inoculated cacao saplings used 2.6 and 2.1%, respectively, of N added to the pots in leaf litter and 12.1 and 7.1% of N available in root litter indicating that root litter of I. edulis may be a more efficient N source than leaf litter for cacao. Although the fungicide treatment did not completely suppress AMF in non-inoculated pots, it created sufficient contrast in root AMF colonisation for concluding that AMF significantly enhanced cacao N use from both litter types. The role of root litter of shade trees as a N source in agroforestry should not be neglected.     

Methylene urea as a slow-release nitrogen source for processing tomatoes

The potential for improved fertilizer N use efficiency was tested using a slow release N fertilizer, methylene urea (MU), on processing tomato (Lycopersicon esculentum Mill.) in a 2-year field study in the Sacramento Valley, California. Fertilizer N use efficiency of urea and a (50:50, w:w) mixture of urea and MU (uMU) was determined in direct-seeded and transplanted tomato plots with winter cover crop (CC) or winter fallow (F) using ¹⁵N labeled fertilizers. Residual MU-N was estimated from tomato N uptake in the ¹⁵N microplots, and from residual ¹⁵N uptake of wheat grown after two tomato crops. No significant differences were found in the quantity and quality of tomato yields among fertilizer and management treatments during the first year. Total yields in transplanted FuMU plots were significantly lower in the second test year, suggesting slow mineralization of MU-N in the F treatment. On average, about 40% of added fertilizer N was taken up in both fertilizer treatments, and the recovery of ¹⁵N in plant biomass and soil was 75–96 and 50–74% in seeded and transplanted blocks, respectively. In the laboratory, mineralization of MU started faster in soils with past MU use, but the enhanced mineralization did not affect the plant N uptake in the field. MU is potentially an environmentally attractive fertilizer, but without an immediate increase in yield and N use efficiency compared to conventional fertilizers, its use on row crops may not be economically feasible unless the positive environmental factors like decreased leaching of N are considered.     

Guano as a nitrogen source for fertigation in organic farming

Guano is a natural organic fertilizer used in organic farming management when supplementary nitrogen is needed. In modern irrigated agriculture N top dressing is often applied through the irrigation water. The objective of this research was to evaluate the potential of guano as a source of available N when applied through water, compared with application to soil. The release of mineral and total soluble N from guano to water was monitored, as a function of time, under laboratory conditions, and compared with mineralization of guano in soils. The effect of guano:water ratio, aeration of the mixtures, addition of rock-phosphate or clay minerals, and temperature on the composition of the solutions was determined. Guano released more than 90% of its N content into solution during 10 d at a guano:water ratio of 1:10 at 27°C. The release of soluble N, of which 85% was NH₄-N, was linked with an increase of pH from 7.0 to 8.5 or more. None of the treatments increased the rate or the total N release beyond that. Suboptimal temperatures, 13.6 ± 4.7°C or 50°C, greatly reduced the rate of guano-N release to solution. The mineralization of guano in soil was more rapid than in water, but the total N release was the same, leading to the conclusion that the application of guano through the irrigation water may be as efficient as directly to soil, provided sufficient time for fermentation is allowed.Contribution from the ARO, The Volcani Center, Bet Dagan 50250, Israel, no. 3290-E, 1991 series.     

Spent mushroom compost as a nitrogen source for spring barley

Spent mushroom compost (SMC) contains a range of plant nutrients, including nitrogen (N), a large proportion of which originate from arable crops. Using SMC as an organic fertilizer for crops recycles these nutrients. Effective use of SMC in fertilizer regimes requires knowledge of the nitrogen fertilizer value (NFV) of the SMC, which is the amount of mineral fertilizer N required to give the same N yield, or marketable yield, as an application of SMC. The objectives of these experiments were to evaluate the effect of SMC on spring barley grain yield and quality and to determine its NFV. Experiments were carried out on two soils, light- and medium-textured, over 3 years (2008–2010). The experiments compared the yield response and N uptake of spring barley to fertilizer N with and without SMC. SMC application gave similar or higher grain yield and N uptake compared to fertilizer only treatments at corresponding fertilizer N rates. SMC had no significant (P > 0.05) effect on the economic optimum fertilizer N rate but the maximum yield was significantly (P < 0.05) higher where SMC was applied in two of the six experiments. Effects of SMC on grain quality were small. Results indicated that the NFV, expressed as a proportion of the total N applied in SMC, ranged from 0.05 to 0.29 kg kg^?1 N applied in SMC, with a mean of 0.15 kg kg^?1. It is concluded that SMC can contribute to the nitrogen nutrition of small grain cereal crops in high yield potential environments.     

A conceptual assessment of the importance of denitrification as a source of soil nitrogen loss in tropical agro-ecosystems

This paper attempts to answer the question: is denitrification a major route of N loss from tropical agro-ecosystems? This question turns out to be very difficult to answer due to a severe shortage of data on this process for tropical agro-ecosystems other than rice. Given this lack of data, I approach this question by analyzing data on denitrification and nitrous oxide flux in tropical native forest and pasture soils and attempt to make some conclusions and pose some hypotheses about the significance of denitrification in tropical agricultural soils. I also briefly review methods for measuring denitrification. The data analysis suggests that denitrification in tropical forest soils is strongly influenced by the nature and amount of soil C and N turnover. Studies to examine differences in denitrification in different tropical agricultural systems should focus on the effects of system management on C and N turnover. The data analysis also suggests that, just as in temperate regions, denitrification may not be a significant route of N loss from most tropical agricultural systems. However, field studies are necessary to determine if this is actually the case.     

Biological nitrogen fixation in tropical dry forests with different legume diversity and abundance

Tropical dry forests have high diversity and plant abundance of potentially biologically nitrogen fixing (BNF) legume species, attributed to the ecological advantage of fixation. However, there are few estimates of N quantities annually fixed, hindering the understanding of factors that control BNF, like low phosphorus availability. The quantities of N fixed in three dry forest (caatinga) fragments of the semiarid Brazilian northeastern region with different legume plant proportions were determined and seedlings of Mimosa tenuiflora were grown with phosphorous fertilized soil from the fragments to verify if lack of fixation was due to the absence of rhizobia populations or P deficiency. The vegetation of all areas was dominated by legume plants, mainly potentially nodulating ones, despite the relatively high soil N availability. M. tenuiflora was the most abundant nodulating legume in all fragments, with annual leaf productions from 800 to 1400 kg ha^?1. BNF amounts were low (1.4, 18 and 3.6 kg ha^?1 year^?1 in the mature caatinga of Petrolina and in the mature and regenerating caatingas of São João, respectively) considering the high proportions of potentially nodulating plants (33, 61 and 82% of total plant basal area), because 80, 10 and 70% of these plants were not fixing and those fixing had only 20–46% of their N derived from the atmosphere. Since the pot grown seedlings nodulated abundantly, the low BNF could not be explained by absence of microsymbionts but likely to low symbiosis efficiency due to relatively high N and low P availability.     

Relationships between rhizobial diversity and host legume nodulation and nitrogen fixation in tropical ecosystems

With recent advances in rhizobial phylogeny, questions are being asked as to how an ecological framework can be developed so that rhizobial classification and diversity could have greater practical applications in enhancing agricultural productivity in tropical ecosystems. Using the results of studies on tropical rhizobia which nodulate agroforestry tree legumes, three ecological aspects of rhizobial biodiversity were used to illustrate how its potential can be exploited. The results showed that legumes nodulate with diverse rhizobial types, thus contributing to the success of legumes in colonising a wide range of environments. There was an apparent shift in the relative dominance of rhizobia populations by different rhizobial types as soil pH changed. The Rhizobium tropici-type rhizobia were predominant under acidic conditions, Mesorhizobium spp. at intermediate pH and Sinorhizobium spp. under alkaline conditions. The R. tropici-type rhizobia were the most effective symbiotic group on all the host legumes. However, strains of Sinorhizobium spp. were as effective as the R. tropici types in N₂-fixation on Gliricidia sepium, Calliandra calothyrsus and Leucaena leucocephala; while Mesorhizobium strains were equally as effective as the R. tropici types on Sesbania sesban. Classification of rhizobia based on phenotypic properties showed a broad correlation with groupings based on 16S rRNA sequence analysis, although a few variant strains nested with the dominant groups in most of the clusters. Some of the phenotypic characters that differentiated different rhizobial groups are highlighted and a case is made for the need to standardise this method.     

Nitrous oxide emissions as influenced by legume cover crops and nitrogen fertilization

In this study, we measured nitrous oxide (N₂O) fluxes from plots of fall-planted hairy vetch (HV, Vicia villosa) and spring-planted broadleaf vetch (BLV, Vicia narbonensis) grown as nitrogen (N) sources for following summer forage crabgrass (Digitaria sanguinalis). Comparisons also included 60 kg ha^?1 inorganic N fertilizer for crabgrass at planting (60-N) and a control without N fertilizer. Each treatment had six replicated plots across the slope. Fluxes were measured with closed chamber systems during the period between spring growth of cover crops and first-cut of crabgrass in mid-July. HV had strong stand and aboveground biomass had 185?±?50 kg N ha^?1 (mean?±?standard error, n?=?6) at termination. However, BLV did not establish well and aboveground biomass had only 35?±?15 kg N ha^?1. Ratio vegetation index of crabgrass measured as proxy of biomass growth was highest in HV treatment. However, total aboveground biomass of crabgrass was statistically similar to 60-N plots. Fluxes of N₂O were low prior to termination of cover crops but were as high as 8.2 kg N₂O ha^?1 day^?1 from HV plots after termination. The fluxes were enhanced by large rainfall events recorded after biomass incorporation. Rainfall enhanced N₂O fluxes were also observed in other treatments, but their magnitudes were much smaller. The high N₂O fluxes from HV plots contributed to emissions of 30.3?±?12.4 kg N₂O ha^?1 within 30 days of biomass incorporation. Emissions were only 2.0?±?0.7, 3.4?±?1.3 and 1.0?±?0.4 kg N₂O ha^?1 from BLV, 60-N and control plots, respectively.     

Nitrogen in coal as a source of nitrogen oxide emission from furnaces

In this paper are presented some experimental results on the conversion of fuel-nitrogen to nitric oxide in both diffusion and premixed flames, and the results are used to speculate on mechanisms of nitric oxide formation. Models of pulverized-coal combustion are reviewed and used to examine the conditions under which fuel-nitrogen contributes significantly to nitric oxide emission. Mechanisms are suggested to explain why fuel-nitrogen contributes most of the emission from fluidized-bed combustors but only a small fraction of the emission from pulverized-coal flames.     

Optimizing soil nitrogen balance in a potato cropping system through legume intercropping

Nutrient Cycling in Agroecosystems - Negative nitrogen balance represents a major factor causing low potato yield in potato growing areas of Kenya while its excessive surplus poses a significant...     

Alternatives for nitrogen nutrition of crops in tropical agriculture

The development of sustainable agricultural systems for the tropics requires among other technologies, alternatives for nitrogen fertilizers which are often limited in availability for financial reasons and also represent a major source of groundwater and air pollution. There are many new alternatives for the development of agricultural systems which make use of biological processes in soil. Biological nitrogen fixation (BNF), that is, the biological conversion of atmospheric dinitrogen into mineral N, is the most important alternative among them. Examples are given of the impact of various technologies used in Brazil. Soybean, introduced into the country 30 years ago, is now the second most important export crop, reaching 24 million tons annually with no N fertilizer application. Consequently, Brazil today is the country in the world which uses the lowest amounts of nitrogen fertilizers in relation to phosphate. Alternatives for crop rotations and pastures are also discussed. Possibilities of expanding BNF to cereals and other non-legume crops are gaining new credibility due to the identification of endophytic associations with diazotropic bacteria. The definite proof of substantial BNF in sugar cane with N balance and¹⁵N methods in certain genotypes selected under low N fertilizer applications opens up new alternatives for sustainable agriculture and will be the key to viable bio-fuel programmes.     

Use ofLeucaena leucocephala (Lam. de Wit) leaves as a nitrogen source for crop production

Field and pot trials were conducted to determine optimum management practices for usingLeucaena leucocephala (Lam. de Wit) leaves as a N source for crop production. Field trials with maize showed no benefit from split application of leucaena leaves or from application of fresh as opposed to dried material. Field trials also failed to show any difference between incorporation as opposed to surface application of leucaena leaves. This may be attributed to the low nitrogen response observed. Pot trials however, showed that soil incorporation of leucaena leaves was more effective than surface application in increasing plant dry weight.Leucaena leaves were not as effective as inorganic N in increasing maize grain yield (field trials) or dry matter production (pot trial). Unlike inorganic N, leucaena leaves had a significant residual effect on the succeeding maize crop. In decomposition studies, buried leucaena leaves decomposed more quickly than surface-applied leaves, and fresh leaves decomposed more rapidly than dried leaves.     

High-pressure high-temperature synthesis of GaN with melamine as the nitrogen source

Micron-sized grains of gallium nitride (GaN) crystallizing in the Wurtzite phase were synthesized through a chemical reaction between gallium (Ga) metal and melamine (C₃N₆H₆). The reaction occurred at the temperature range from 1073 to 1473 K and the pressure range from 3.5 to 5.5 GPa. X-ray diffraction (XRD) and transmission electron microscopy (TEM) investigations showed that the final black products mainly contained the clusters of tiny GaN crystals. Prism-like well-shaped single crystals were found in the TEM micrographs. A vapor–liquid–solid growth process was proposed to explain the growth mechanism of GaN in which the pyrolysis of melamine was responsible for the provision of reactive nitrogen.     

Meat and bone meal as nitrogen and phosphorus fertilizer to cereals and rye grass

Meat and bone meal (MBM) contains appreciable amounts of total nitrogen (~8%), phosphorus (~5%) and calcium (~10%). It may therefore be a useful fertilizer for various crops. This paper shows results from both pot and field experiments on the N and P effects of MBM. In two field experiments with spring wheat, increasing amounts of MBM (500, 1000, 2000 kg MBM ha⁻¹) showed a linear yield increase related to the N-supply. A similar experiment with barley gave positive yield increase for 500 kg MBM ha⁻¹ and no further yield increase for larger amounts of MBM. Supply of extra mineral P gave no yield increase when 500 kg MBM ha⁻¹ or more was applied. Meat and bone meal as P fertilizer was studied in greenhouse experiments using spring barley and rye grass as test crops. N applications were 100 N kg ha⁻¹ to barley and 200 kg N ha⁻¹ to rye grass, either from mineral fertilizer or assuming that 80% of total N in MBM was effective. Four different P deficient soils were given increasing doses of MBM and compared with compound NPK fertilizer 11-5-18, mineral N fertilizer (0 kg P ha⁻¹) and a control (0 kg N ha⁻¹, 0 kg P ha⁻¹). In barley there was no significant yield difference between the NPK treatment and MBM treatment with equal N supply, and both had significant higher yield than the treatment receiving the same amount of mineral N without P-supply. The positive yield response of MBM was even larger in rye grass. Both in barley and rye grass a significant residual effect of P from MBM applied the year before was found when the treatments received the same amount of mineral N fertilizer (0 kg P ha⁻¹). The pot experiments confirmed the assumed N effect of MBM. When MBM is used according to the N demand of the crops, the P supply will be more than sufficient and residual P will be left in the soil. Since a part of this residual P was utilized by the crops of the following year, it is not recommended to apply P-fertilizer the year after MBM application.     

改性碳铵为氮源的复混肥施用技术研究

碳铵加入稳定剂,改善物性,增强稳定性,提高了肥效.玉米、水稻专用肥与对照(空白)比,玉米增产18.5%,水稻增产30.6%.玉米、水稻专用肥与等价格磷酸二铵比,玉米专用肥增产7.8%,水稻专用肥增产10.3%.玉米、水稻专用肥最佳用量600～660/hm2.     

Corn intercropped with tropical perennial grasses as affected by sidedress nitrogen application rates

Nutrient Cycling in Agroecosystems - In tropical regions, one of the primary difficulties in the sustainability of no-till systems is the maintenance of soil cover throughout the year....     

Chiastolite ores as a source for refractory production

Ore samples of the Bezymyanskoe deposit in the Kemerovo Region containing about 20% chiastolite (A1₂O₃ · SiO₂) are studied. It is shown that the ore can be enriched for the production of concentrate for highalumina refractories.     

Crambe meal as a protein source for feeds

Crambe abyssinica may be grown for its seed oil containing 55-60% erucic acid, which fills a long-term, technologically important US industrial market. The residual meal could serve in animal feeds, but, like other Cruciferae, crambe seed contains glucosinolates that limit the feed value of the defatted meal. Protein content, amino acid composition, protein efficiency tests and numerous animal feeding experiments show that crambe meal contains protein of good nutritional quality. Means of reducing, nullifying or removing the glucosinolates and their hydrolysis (aglucon) products have been the object of many studies, and crambe meals containing native levels of glucosinolates and/or aglucon products have been shown to be lethal to mice, rats and chicks when fed at significant dietary levels. Animal performance is inversely related to sublethal concen-trations of these compounds in modified meals. However, water-extracted crambe meals have excellent nutritional quality when such extraction removes the glucosinolates and/or aglucon products. Feeding experiments suggest that these meals, although more costly to prepare, could be used in feeds for nonruminant animals. On the other hand, moist heat-toasting of crambe meals in conventional oilseed extraction facilities provides meals of value for supplemental protein in beef rations. For this use, specifications and FDA ap-proval are in place for commercial exploitation of crambe meal. These studies and the status of crambe as a protein source in feeds are reviewed.     

Prospects for sphagnum peat as a source of fullerenes

The modification of slightly decomposed sphagnum peat for the synthesis of fullerenes is considered. Topographic images of the carbon nanotubes first synthesized on that basis are presented.     

Ammonia as a source of hydrogen for hardening oils

Summary and Conclusions Equipment for dissociating or “cracking” ammonia has been developed to deliver catalytically pure hydrogen under pressure. The cracker is practically automatic in operation, occupies but small space, and can be built to meet a wide range of capacity operating at high economy. While it is not claimed that cracked ammonia is the preferred source of hydrogen for large outputs, it should be considered for any requirement of less than 1,000 cu. ft. per hour, and in some cases for requirements of 1,000 cu. ft. and more. Cracked ammonia has been demonstrated to be suitable for hardening oils, and affords a source of cheap hydrogen with a minimum investment for those who desire to operate on small scale or who desire to decentralize large operations.