Differences In Soil Fertility Research Articles

Composted biochar versus compost with biochar: effects on soil properties and plant growth

Biochar is widely recognized as an amendment that enhances soil properties and sequesters carbon, particularly in degraded soils. However, biochar applied solely to soil may also hinder plant development due to toxic by-products generated during pyrolysis or nutrient retention. To mitigate these adverse effects, it has been suggested to either mix biochar with compost or to process it by composting with fresh organic materials. To date, there is a lack of comparative studies evaluating the performance of these two approaches. In this study, three types of biochar, differing in their initial feedstocks (beech wood, hornbeam/beech/oak mixture, and digestate/cereal straw mixture), were investigated. These biochars were applied solely, mixed with green waste compost, or processed as composted biochar in two soils of different fertility (a Luvisol and a gleyic Fluvisol). A pot experiment was conducted under controlled conditions where lettuce was grown for three months. After harvesting, plant biomass, and soil microbial and physicochemical properties were measured. Composted biochar and compost additives maintained a neutral soil pH, contrary to biochar applied solely or mixed with compost. The dissolved organic carbon and total nitrogen were higher in composted biochar treatments, leading to a higher proportion of humified material with a high degree of condensed aromatic groups compared to other treatments. Microbial activities were higher in the composted biochar treatments compared to those in the compost with biochar, and more specifically in the less fertile Luvisol. Finally, composted biochar increased plant growth by almost six times compared to the control without amendments, whereas the mix of biochar and compost increased it by only three times. Solely applied biochars did not affect lettuce growth. This study demonstrates that biochar composting is more beneficial than mixing biochar with compost in terms of improving soil fertility and mitigating the negative effects associated with pure biochar application.Graphical

Влияние аэротехногенных выбросов магнезитового производства на надземную фитомассу Betula pendula Roth в зависимости от плодородия почвы

The study of the test crop European birch elevated phytomass at the magnesite production impact zone (the Southern Urals, Satka) was carried out. Two plots of test crops of the same age (created in 1983) growing 3 km away from the source of technogenic pollution from magnesite production and with different soil fertility were studied. The elevated phytomass of the stand was calculated using sample trees. The selection of trees was carried out from different thickness levels within the entire range. A regression method was used to estimate the phytomass of the stand. In the course of our work, we tested the null hypothesis that soil fertility is a significant factor for the adaptation of the Betula pendula Roth to pollution since it was noted that stands on rich soils have the best growth (height, diameter) and the vital condition of the stand. A comparative analysis of the elevated phytomass of test crops with the same level of pollution by magnesite production emissions, but growing on soils of different fertility, allowed us to assess the effect of the soil factor on the ability of the European birch to adapt to technogenic pollution. Under the conditions of magnesite production emissions, the elevated phytomass of experimental Betula pendula Roth crops growing on highly fertile soils is not reduced to the same extent as that of birch growing on low-fertile soils. Under the negative emissions impact, the mass of wood and branches of the Betula pendula Roth growing on highly fertile soils decreases to a smaller extent than the mass of other fractions. The wood and branches weight of the Betula pendula Roth growing on highly fertile soils is 3.8 and 3.0 times higher, respectively, and the weight of leaves and bark is 2.3 and 2.4 respectively, compared with test plot No. 5 on low-fertile soils.

INFLUENCE OF SOIL FERTILITY ON THE ABILITY OF SCOTS PINE (Pinus sylvestris L.) TO ADAPT TO TECHNOGENIC POLLUTION

ABSTRACT The purpose of the research is to identify the effect of soil factor on the ability of Scots pine to adapt to technogenic pollution based on comparative analysis of radial increment of the species which grows on soils of different fertility. The null hypothesis that soil fertility is a significant factor for adaptation was tested. The research area i.e. the plantation created in 1983 and exposed to pollution of aero-technogenic emissions of magnesium production Satka/Chelyabinsk Region/Russia, is located within the central part of the subzone of coniferous-broad-leaved and South-taiga coniferous forests of the Southern Urals. The analysis of annual growth rings (AGR) of Scots pine growing on soils of different fertility allowed us to estimate the effect of soil factor on the ability of Scots pine to adapt to magnesite pollution. As results of the research it was found that the differences in the AGR of Scots pine growing on soils of different fertility was statistically significant under the same level of technogenic pollution. During the investigation period (1994-2010), the AGR of Scots pine on fertile soils were significantly higher than those of on poor soils for 7 years. It was revealed that the positive effect of soil fertility on the Scots pine growth is leveled at the level of pollution exceeding 6-10 thousand tons per year of gaseous emissions and 25-30 thousand tons per year of total emissions. It was also found that soil fertility allows better adaptation of Scots pine to low temperatures, and more actively grow on sites with increasing precipitation.

Invasions of <i>Bidens frondosa</i> L. (Asteraceae) in communities of saline soils of south-east Europe

Bidens frondosa is an invasive xenophyte which is naturalized in vegetative communities on the territory of the Southeast of Europe. The natural area of B. frondosa is in the North America. The secondary one is on the territory of Eurasia, here B. frondosa forces out native B. tripartita that is explained by competitive superiority of the North American species on growth rates and seed efficiency on soils of different fertility and water regime. In the secondary area in Eurasia B. frondosa grows on banks of reservoirs and water currents as well as on other damp habitats (including disturbed ones) often in large quantities. This species is also found on saline soils of the European Southeast. It is registered in communities of association Atriplici aucheri-Tamaricetum ramosissimae Golub et al. 1998 belonging to class Nerio-Tamaricetea Br.-Bl. et Bols 1958 order Tamaricetalia ramosissimae Golub in Barmin 2001 alliance Elytrigio repentis-Tamaricion ramosissimae Golub in Barmin 2001, in one of its subassociations A.au.-T.r. althaeetosum Golub et al. 1998, but there B. frondosa is the diagnostic taxon as well as the constant species that is met in all of its described coenosis.

Effects of wheat straw mulch application and nitrogen management on rice root growth, dry matter accumulation and rice quality in soils of different fertility

The root is the most sensitive part of the plant. This study examined the effects of wheat straw mulch, nitrogen (N) management and soil fertility on rice root morphology, dry matter accumulation, grain yield and rice quality and explored the correlation between root morphology and rice quality indexes. Wheat straw mulch had an obvious inhibitory effect on rice root morphology, especially on the total root length and total root surface area at 20 days after transplanting in the high- and low-fertility soil. The low-fertility soil treatments had higher levels of inhibition. However, straw mulch significantly promoted root growth, increased dry matter accumulation in the subsequent growth periods and improved the grain yield and rice quality, which mainly reduced the percentage of chalky kernels and the chalkiness degree. Increasing the nitrogen fertilizer percentage applied as a basal or tillering fertilizer reduced the inhibition in the early growth period; for balanced rice root growth, dry matter accumulation, grain yield and rice quality, 30% as basal fertilizer, 30% as tillering fertilizer and 40% as panicle fertilizer were the best N management strategy. Correlation analysis showed that the rice quality was extremely significantly positively correlated (r = 0.30–0.59, P < 0.05) with the root morphology indexes of the brown rice and protein contents and was significantly or extremely negatively correlated (r = − 0.73 to − 0.28, P < 0.05) with the length–width ratio, percentage of chalky kernels, chalkiness degree and amylose content.

Differences between nitrogen-tolerant and nitrogen-susceptible sweetpotato cultivars in photosynthate distribution and transport under different nitrogen conditions.

To characterize the differences in photosynthate distribution and transport between nitrogen(N)-tolerant and N-susceptible sweetpotato cultivars under different N conditions, three N levels, including 0 (N0), 120 (N120), and 240 kg ha−1 (N240), were used in field experiments with the Jishu26 (J26) and Xushu32 (X32) cultivars in 2015 and 2016. The results from both years revealed that high N application reduced the tuberous root yield, the tuber/vine rate of carbon-13 (13C), and top-to-base (three equal segments of stem divided from the fifth opened leaf of the shoot tip to the main stem, defined as the top, middle, and base parts, respectively) gradients such as sucrose, ammonia N and potassium along the stem. ‘J26’ showed a higher yield than ‘X32’ under N0 but lower yield than ‘X32’ under N120 and N240. It also exhibited a higher 13C distribution to tuberous roots compared with that of ‘X32’ under N0, and the opposite trend was observed under N120 and N240. Under N0, ‘J26’ showed a steep top-to-base amino acid gradient and a significantly lower top-to-base sucrose increase along the stem in the late growth stage. Under N120 and N240, ‘X32’ exhibited a greater top-to-base decrease in the ammonia N along the stem during the main growth stages, a steep top-to-base sucrose gradient along the stem in the early growth stage, and a lower top-to-base sucrose increase along the stem in the middle and late growth stages. The formation of a reasonable photosynthate distribution structure attributed to high yield was related to a desirable sucrose, ammonia N or K+ gradient downward along the stem. These results might help provide farmers with sweetpotato cultivars using less or no N fertilizer in soils of different fertility and enhance the knowledge of yield-related physiology.

Mineral Nutrition of Young Ash in Latvia

Abstract The research objectives were: 1) to determine healthy young ash supply with nutrients and their concentrations in natural growth conditions; 2) to estimate nutrient balance and inter-correlations within a system “soil-plants”; and 3) to determine the potential effect of environmental conditions (forest type, plant phytosociological group, soil group, etc.) on nutrient accumulation in soil and leaves of young ash. The investigation was conducted in 28 different forest sites with young ash in Latvia. The results demonstrated that young ash grows well on a wide range of site types in terms of soil composition, forest type and phytosociological tree group. Although highly heterogeneous, soil in ash stands in Latvia can provide a sufficient supply of nutrients. Therefore, the nutrient status of healthy young ash leaves can be characterized as sufficient, although low levels of P, Zn, and K in leaves was found for most sites. Significant impact of soil group and forest type was found on nutrient composition of ash soil, while leaf nutrient concentrations were more dependent on the forest type and phytosociological tree group. The obtained results confirmed the ability of ash to accumulate nutrients within a certain range from soils of different fertility, organic matter content and soil reaction in Latvia.

Decomposition Dynamics of Soybean Residues in Two Soils of Different Fertility

Decomposition Dynamics of Soybean Residues in Two Soils of Different Fertility

Effects of Organic-Manure Application on Growth, Grain Yield, and Nitrogen, Phosphorus, and Potassium Recoveries of Rice Variety Manawthuka in Paddy Soils of Differing Fertility

A 2-year pot experiment (2005–2006) was conducted in a greenhouse using rice variety Manawthuka on high-fertility Kasuya soil and low-fertility Futsukaichi soil. Fermented cow manure (CM) and poultry manure (PM) were applied as organic nitrogen (N) sources. In every manure application, 20 kg urea ha–1 was also applied at basal. Dry matter, grain yield, and nitrogen uptake were greater in PM than CM and significantly greater in Kasuya soil. In 2006, they increased in Futsukaichi soil but decreased in Kasuya soil. Apparent nitrogen recovery was greater in PM than in CM and increased in both soils in 2006 because of residual benefits from manure application. The apparent phosphorus recovery was greater in CM than in PM; however, large plant phosphorus accumulation was observed in PM. In both soils, the efficiency of CM is very low, and CM-only application is unlikely to achieve an optimal rice yield in the short term.

The effect of bovine saliva on growth attributes and forage quality of two contrasting cool season perennial grasses grown in three soils of different fertility

The aim of this study was to determine the response of Dactylis glomerata L. (Orchardgrass) and Festuca ovina L. (Sheep fescue), to bovine saliva application in a loamy soil (most fertile), a sandy loam and a sandy soil (least fertile). The effects of cutting and cutting + saliva on relative height growth rate (RHGR), above- and belowground biomass and forage quality attributes [crude protein, NDF (neutral detergent fibre) and ADF (acid detergent fibre)] were investigated. The results showed that the cutting and cutting + saliva treatments resulted in greater RHGR than the control, but only with D. glomerata in the sandy soil did the application of saliva increase the RHGR. However, saliva applied after cutting increased the aboveground biomass averaged over all species and all three soils. Saliva applied to D. glomerata increased the belowground biomass in the sandy loam and sandy soils but decreased it in F. ovina in the sandy soil. The application of saliva had no effect on the crude protein or the NDF content of either species in any of the soils. On the other hand, the application of saliva after clipping increased the ADF of F. ovina but decreased that of D. glomerata averaged over all three soils. Averaged over both species, the ADF was increased by the addition of saliva in the sandy soil, had no significant effect in the sandy loam (P &gt; 0.05) and was slightly increased in the loam.

Enzyme activity in forest peat soils

The aim of the study was to determine the activity of dehydrogenases and urease in forest peat soils of different fertility. There were selected 23 experimental plots localised in central and northern Poland. The research was conducted on forest fens, transition bogs and raised bogs. The biggest differences in soil physical and chemical properties were detected between fen and raised bog soils while raised bog soils and transition bog soils differed the least. Statistically significant differences between particular subtypes of peat soils were observed for soil pH-H2O, pH-KCl, C/N ratio as well as the content of organic carbon, nitrogen, calcium and potassium. The highest average dehydrogenase activity in the soil surface level was observed in fen soils, and the lowest – in raised bogs soils. The results obtained on urease activity were similar. Differences in urease activity in the studied soil types were shown. Dehydrogenase activity did not reveal statistically significant diversity. The activity of urease was negatively correlated with the content of carbon, C/N ratio, hydrolytic acidity and moisture. Also the increase in enzymatic activity accompanied by the increase in pH has been observed.

Vegetation composition promotes carbon and nitrogen storage in model grassland communities of contrasting soil fertility

Summary 1. The benefits of plant functional group and plant species diversity for sustaining primary productivity have been extensively studied. However, few studies have simultaneously explored potential benefits of plant species and functional group richness and composition for the delivery of other ecosystem services and their dependency on resource availability. 2. Here, we investigated in soils of different fertility the effects of plant species and functional group richness and composition on carbon (C) and nitrogen (N) stocks in vegetation, soil and soil microbes and on CO2 exchange and the loss of C and N from soil through leaching. We established plant communities from a pool of six mesotrophic grassland species belonging to one of three functional groups (C3 grasses, forbs and legumes) in two soils of contrasting fertility. We varied species richness using one, two, three or six species and one, two or three functional groups. 3. After 2 years, vegetation C and N and soil microbial biomass were greater in the more fertile soil and increased significantly with greater numbers of plant species and functional group richness. The positive effect of plant diversity on vegetation C and N coincided with reduced loss of water and N through leaching, which was especially governed by forbs, and increased rates of net ecosystem CO2 exchange. 4. Soil C and N pools were not affected by the number of plant species or functional group richness per se after 2 years, but were enhanced by the presence and biomass of the legumes Lotus corniculatus and Trifolium repens. 5. Synthesis. Collectively, our findings indicate that changes in plant species and functional group richness influence the storage and loss of both C and N in model grassland communities but that these responses are related to the presence and biomass of certain plant species, notably N fixers and forbs. Our results therefore suggest that the co‐occurrence of species from specific functional groups is crucial for the maintenance of multifunctionality with respect to C and N storage in grasslands.

Release of mineral nutrients and heavy metals from wood and peat ash fertilizers: Field studies in Finnish forest soils

Two field trials were conducted to study the rate of release of nutrients and heavy metals from wood and peat ash fertilizers in forest soils. In the first experiment, ash particle residues were extracted from peat and mineral soils 3 and 5 years after spreading and analysed for changes in element concentrations. Dissolution of different ash fertilizer products was also estimated by measuring the changes over time in the recovery of added nutrients and heavy metals in the surface of two peat soils. The results showed that potassium (K), sodium (Na), boron and sulfur are easily released from wood ash, whereas heavy metals are highly insoluble in all types of ash fertilizer products. Granulated ash fertilizers were less soluble than powdered fertilizers and the products stabilized by self-hardening. Minor differences occurred in ash fertilizer dissolution between peat and mineral soils and soils of different fertility. The most significant difference between wood and peat ash concerning their dissolution was the low solubility of K and Na in peat ash. Given the very slow dissolution of ash fertilizers, long-term studies are needed to understand fully the effect of ash fertilization on nutrient and heavy metal cycling in forest ecosystems.

The impacts of individual plant species on rhizosphere microbial communities in soils of different fertility

To investigate the effects of individual plant species on microbial community properties in soils of differing fertility, a microcosm experiment was carried out using plant species representative of the dominant flora in semi-fertile temperate grasslands of northern England. Soil microbial biomass and activity were found to be significantly greater in the more fertile, agriculturally improved soil than in the less productive unimproved meadow soil. Differences in microbial community structure were also evident between the two soils, with fungal abundance being greater in the unimproved soil type. Individual plant species effects significantly differed between the two soils. Holcus lanatus and Anthoxanthum odoratum stimulated microbial biomass in the improved soil type, but negatively affected this measure in the unimproved soil. In both soil types, herb species generally had negative effects on microbial biomass. Patterns for microbial activity were less consistent, but as with microbial biomass, A. odoratum and H. lanatus promoted respiration, whereas the herbs negatively affected this measure. All plant species grown in the improved soil increased the abundance of fatty acids synthesised by bacteria (bacterial phospholipid fatty acid analysis) relative to bare soil, but they negatively impacted on this group of fatty acids in unimproved soil. Similarly, the abundance of the fungal fatty acid 18:2ω6 was increased by all plants in the more fertile improved soil only, albeit non-significantly. Our data indicate that effects of plant species on microbial properties differ markedly in soils of differing fertility, making general predictions about how individual plants impact on soil properties difficult to make.

Plant phenology and soil fertility effects on below-ground carbon allocation for an annual ( Bromus madritensis) and a perennial ( Bromus erectus) grass species

Plant strategies for using available resources were explored through a comparative analysis of C allocation and use in the rhizosphere. The seasonal dynamics of plant C partitioning was compared for annual and perennial species of bromegrass ( Bromus madritensis and B. erectus) in soils of different fertility using successive 2-week labelling with 14CO 2. Measurements of labelled soil CO 2 indicated that current assimilates were readily used by roots and rhizosphere microflora. For vegetative stages of plant growth, there was a regular decrease during the year of carbon translocation from above to below-ground and 10–20% more of net C assimilation was directed toward the roots in the poor soil than in the fertile soil. During reproductive stages, there were drastic decreases to as low as 10 and 25% of net C assimilation reaching below-ground in the annual and perennial species, respectively. Over an entire year, below-ground C allocation in B. madritensis was 37% of net assimilation in the fertile soil and 44% in the poor soil. In B. erectus the figures varied from 42-49 to 60% in the fertile and poor soil, respectively. The proportion of current below-ground C respired and exuded in the rhizosphere was more than 15% higher in the fertile soil than in the poor soil. During reproductive stages, C losses exceeded gain by the roots and the variation from vegetative to reproductive stages reached 30% in B. madritensis (25–57% in poor soil, 45–73% in fertile soil), 20% in B. erectus (39–59% for plants developed from cuttings in the rich soil). In B. erectus, the development of reproductive structures was strongly correlated with soil fertility and a determinant in rhizosphere C budgets. This feature characterised the difference between the annual and perennial species. When expressed in units of C translocated below-ground per unit of root C, the highest C use efficiency was in the poor soil. In B. madritensis, 64% of annual below-ground C allocation remained in the roots in the poor soil, 44% in the fertile soil. In B. erectus, this percentage varied from 62 to 50% between low and high fertility soils. The trade-off between rate of growth and resource use efficiency defined in the literature for above ground plant traits was confirmed below-ground: faster growth rate, higher losses and, therefore, lower resource use efficiency in the rich soil than in the poor soil.

Towards a better understanding of carbon flow in the rhizosphere: a time-dependent approach using carbon-14

Controversies exist in interpreting rhizosphere C flow obtained by different 14CO2 labelling methods. However, there is a need for the standardisation of methods in order to be able to compare values obtained for different plants, different stages of development and different habitats. Perennial bromegrass (Bromus erectus Huds) grown in soils of different fertility was exposed to a 14CO2 atmosphere for different periods of time: 1 h, 298 h and 78 days. The evolution of 14CO2 in the soil was measured during and after labelling. The 14C contents of plant and rhizosphere compartments were then estimated. The time-sequence of the rate of 14CO2 evolution after 1 h of labelling, indicated a maximum after around 20 h, followed by an exponential decrease. When expressed as a percentage of net 14C assimilation, root-soil respiration accounted for 14% and 18% in the nutrient-poor and nutrient-rich soils, respectively. Integration of the hourly values over several days showed that the dynamics of the evolution rate were similar for the 298-h and 78-day experiments, thus indicating that rhizosphere C flow was dominated by newly assimilated C. This was confirmed by the proportions of below-ground 14C, measured for roots, respiration and soil, which were not significantly affected by the labelling regime. The differences were, however, found to be significant between the two types of soils. The conclusion was that the conditions for plant growth during labelling were more important than the length of time of labelling, and that this explained the discrepancies in the literature-cited values. A succession of short-term 14C labelling of plants at different development stages followed by an allocation period of about 1 week is proposed to give a reliable estimation of the dynamics of C flow in the rhizosphere.

The impact of elevated CO2 on plant-herbivore interactions: experimental evidence of moderating effects at the community level.

Surprisingly little research has been published on the responses to elevated [CO2] at the community level, where herbivores can select their preferred food. We investigated the combined effects of atmospheric [CO2] and herbivory on synthesised plant communities growing on soils of different fertility. Factorial combinations of two [CO2] (350 or 700 [Formula: see text]l l-1), two fertility (fertilised or non-fertilised), and two herbivory (herbivores present or absent) treatments were applied to a standard mixture of seven fast- and eight slow-growing plants in outdoor microcosms. The herbivores used were the grain aphid (Sitobion avenae) and the garden snail (Helix aspersa). We measured plant biomass, foliar nitrogen and soluble tannin concentration, aphid fecundity, and snail growth, fecundity, and feeding preferences over one growing season. Elevated [CO2] did not have a significant impact on (1) the combined biomass of fast-growing or slow-growing plants, (2) herbivore feeding preferences, or (3) herbivore fitness. There was, however, a significant biomass increase of Carex flacca (which represented in all cases less than 5% of total live biomass), and some chemical changes in unpalatable plants under elevated [CO2]. The herbivory treatment significantly increased the biomass of slow-growing plants over fast-growing plants, whereas fertilisation significantly increased the abundance of fast-growing plants over slow-growing plants. Predictions on the effects of elevated [CO2] based on published single-species experiments were not supported by the results of this microcosm study.

Root competition in soils of different fertility: a paradox resolved?

Root competition in soils of different fertility: a paradox resolved?

Genecological studies of groundsel (Senecio vulgaris L.)

summaryIn a well‐weeded site, selection is likely to favour quick‐maturing variants of annual weeds. Variation in rate of development ‐ from sowing, with synchronous germination, to first flowering and fruiting‐was studied in experiments with Senecio vulgaris L. from the Botanic Garden of Cambridge University, England. Experiments revealed that the number of nodes on the main axis could not be used a ‘genetic marker’ for rate of development.From a large random sample of seed‐parents, progenies were raised from open‐pollinated capitula. Family lines differed significantly in rate of development, with markedly different degrees of variation within families. Twenty family lines, representing the extremes of variation, were chosen for further study. In cultivated selfed derivatives, the majority of the seed‐parents appeared to be behaving as inbred lines for rate of development. Evidence of genetic segregation was detected in only two out of 20 cases. Using the radiate locus as a marker, there was also evidence for a very small amount of outcrossing, with greater values for radiate than non‐radiate seed‐parents. In an experiment in which six inbred lines, derived from the original seed‐parents, were grown out‐of‐doors on fertile and infertile soils and on fertile soil in a glasshouse, there was considerable developmental flexibility in a number of heritable traits including rate of development.Although the methods of weed control in the Botanic Garden would seem to exert a powerful directional selective force favouring only the quickest‐maturing variants of groundsel, a certain amount of variation was nevertheless detected. Many factors are likely to be important in the maintenance of population variation in rate of development in groundsels in the Garden. Several statistically significant lines x soils and lines x places of cultivation were discovered. Thus, the lines did not all behave in the same way in the inside and outside treatments and the rank order of date of maturity of the different lines was not the same in the two soils. This suggests that, in the Garden proper, relative fitness, in the face of weeding pressures, is not fixed but may vary seasonally and in soils of different fertility. This behaviour, in a species which is able to reproduce at all seasons of the year, could be a major factor in the maintenance of population variation. Other contributory factors are of great importance, namely, spatial and seasonal variation in the intensity of weeding, developmental flexibility and the effects of predators, pests and diseases.

An inexpensive cultural system using ash for cultivation of soybean (Glycine max (L.) merrill) on acid clay soils

Several cultural techniques were tested for establishment of nitrogen fixing soybeans on heavy-clay, acid sulfate soils of different fertility at two locations. Holes of 2.5 cm deep were made by inserting a pointed pole into the surface soil. Soybean seeds were dropped into the holes and covered with either (i) Rhizobium inoculant, molybdenum (0.5 kg Mo/ha) and ash from burned rice husks (0.2 t/ha) or (ii) Rhizobium inoculant, molybdenum and local soil instead of the ash. Additional treatments evaluated were the use or absence of tillage and the presence or absence of a rice straw mulch (5 t/ha). Soybean plants treated with ash had the highest number of nodules per plant. The combination of mulching and ash treatments produced the highest soybean grain yields. Without ash all treatments produced low grain yields. Tillage had no effect.