ABSTRACT
Phosphorus (P) reacts with soil minerals, which makes it less available to plants. Considering that Amazonian soils have a low pH and nutrient availability, both of these properties contribute to an increase in P limitation. Here, we investigate how the addition of P to the substrate affects morpho-physiological traits of Brazil nut trees (Bertholletia excelsa Bonpl.). The experiment was carried out in a greenhouse with 24-month-old saplings, and the P treatments consisted of a control (Ferrasol without P addition) and 100, 200, 400, and 500 mg P kg-1 of added to the soil. When B. excelsa saplings were fertilized with phosphate, the N:P leaf ratio reduced from 50 to 26. Addition of P favored the photochemical efficiency of PSII (FV/FM), and the application of 200 mg kg-1 increased photosynthesis (PN) by 50%. Furthermore, phosphorus enhanced light and nutrient use efficiency. An increase in B. excelsa dry biomass was observed when 200 mg P kg-1 was added, with maximum yield occurring at 306.2 mg P kg-1. Physiological parameters suggest robust responses by B. excelsa to P fertilization. In addition, our findings reveal the critical role of P on B. excelsa growth in Ferralsol, as well as the potential of P fertilization to improve functional traits of this important Amazonian tree.
ABSTRACT
In many countries, livestock slurry must be injected or incorporated into the soil to reduce nitrogen losses. However, when the injection is not feasible, farmers adopting conservation practices discard the use of slurry as fertilizer. New approaches related to slurry treatment or application management can stimulate the use of slurry in conservation agriculture (CA). This study aimed to evaluate the agronomic effects of some new management strategies to use dairy slurry for fertilization of ryegrass grown on stubble-covered soil, using as reference standard practices (slurry injection and mineral fertilizer application). The following treatments were considered: (i) bare soil: control (CB), mineral fertilizer (MB), injection (IN); (ii) stubble: control (CS), acidified dairy slurry (ADS), raw dairy slurry (RDS), irrigation following RDS (IR), mineral fertilizer (MS), RDS placed under the stubble (US), raw slurry applied 16 days after sowing (RDS T16). Effects on ryegrass yield, apparent nutrient recovery (ANR) and soil chemical properties were assessed. ADS reached 94% equivalence to MS and performed similarly to IN for productivity, ANR and soil parameters showing to be a sustainable alternative to replace mineral nitrogen and a potential solution to enable dairy slurry application in CA without injection or incorporation into the soil.
ABSTRACT
In general, fertilization recommendations for pepper are old and scarce. Because pepper is a semi-perennial crop with high yield potential and dependence on phosphorus (P), an extremely important element, as it participates in several metabolic processes, it is necessary to look for efficient alternatives for phosphate fertilization, due to its low availability and high adsorption capacity in most Brazilian soils. Slow-release fertilizers have been shown to be an excellent alternative to conventional mineral fertilization. Therefore, the objective of this study was to evaluate the effect of different sources of P on growth and yield of hot pepper (Capsicum frutescens L.). An experiment was carried out in a greenhouse in the JK campus of UFVJM, Diamantina -MG, Brazil, arranged in a completely randomized design with eleven treataments (absence of fertilization, mineral treatment, organic treatment and four slow-release phosphate sources: pelleted organomineral, granulated organomineral, MAP coated and triple formulated, at doses of 150 and 300 kg ha-1 of P2O5). Growth variables, fresh and dry matter accumulation and yield were evaluated 180 days after planting. The pelleted and granulated organomineral treatments at the dose of 300 kg ha-1 of P2O5,promoted the best results for the parameters dry mass of root, number of fruits per plant, fresh and dry mass of fruits and total yield. Such results can be explained by the better efficiency of P release and the better absorption of this nutrient by the plant, making it an excellent option in relation to conventional sources commonly adopted.(AU)
De modo geral, as recomendações para adubação da cultura da pimenta são antigas e escassas. E por se tratar de uma cultura semi-perene com alta produção e dependência de fósforo (P), elemento de suma importância, por participar de diversos processos metabólicos, torna-se necessário buscar alternativas eficientes para a adubação fosfatada, devido a sua baixa disponibilidade e alta capacidade de adsorção na maioria dos solos brasileiros. Os fertilizantes de liberação lenta têm se mostrado como uma excelente alternativa em relação a adubação convencional mineral. Desta forma, objetivou-se avaliar o efeito de diferentes fontes de P no crescimento e produção da pimenta malagueta (Capsicum frutescens L.). Realizou-se um experimento em casa de vegetação no Campus JK da UFVJM, Diamantina -MG, no delineamento inteiramente casualizado com onze tratamentos (ausência de adubação, tratamento mineral, tratamento orgânico e quatro fontes fosfatadas de liberação lenta: organomineral peletizado, organomineral granulado, MAP revestido e formulado triplo, nas doses de 150 e 300 kg ha-1de P2O5). Foram avaliadas variáveis de crescimento, acúmulo de matéria fresca e matéria seca e produtividade aos 180 dias após o transplantio. Os tratamentos organomineral peletizado e granulado 300 kg ha-1de P2O5promoveram os melhores resultados para os parâmetros massa seca do sistema radicular, número total de frutos, massa fresca emassa seca de frutos e produtividade total. Tais resultados podem ser explicados pela melhor eficiência da liberação do P pelos fertilizantes e melhor absorção do nutriente pela planta, tornando-se uma excelente opção em relação as fontes convencionais comumente adotadas.(AU)
Subject(s)
Capsicum/drug effects , Capsicum/growth & development , FertilizersABSTRACT
In general, fertilization recommendations for pepper are old and scarce. Because pepper is a semi-perennial crop with high yield potential and dependence on phosphorus (P), an extremely important element, as it participates in several metabolic processes, it is necessary to look for efficient alternatives for phosphate fertilization, due to its low availability and high adsorption capacity in most Brazilian soils. Slow-release fertilizers have been shown to be an excellent alternative to conventional mineral fertilization. Therefore, the objective of this study was to evaluate the effect of different sources of P on growth and yield of hot pepper (Capsicum frutescens L.). An experiment was carried out in a greenhouse in the JK campus of UFVJM, Diamantina -MG, Brazil, arranged in a completely randomized design with eleven treataments (absence of fertilization, mineral treatment, organic treatment and four slow-release phosphate sources: pelleted organomineral, granulated organomineral, MAP coated and triple formulated, at doses of 150 and 300 kg ha-1 of P2O5). Growth variables, fresh and dry matter accumulation and yield were evaluated 180 days after planting. The pelleted and granulated organomineral treatments at the dose of 300 kg ha-1 of P2O5,promoted the best results for the parameters dry mass of root, number of fruits per plant, fresh and dry mass of fruits and total yield. Such results can be explained by the better efficiency of P release and the better absorption of this nutrient by the plant, making it an excellent option in relation to conventional sources commonly adopted.
De modo geral, as recomendações para adubação da cultura da pimenta são antigas e escassas. E por se tratar de uma cultura semi-perene com alta produção e dependência de fósforo (P), elemento de suma importância, por participar de diversos processos metabólicos, torna-se necessário buscar alternativas eficientes para a adubação fosfatada, devido a sua baixa disponibilidade e alta capacidade de adsorção na maioria dos solos brasileiros. Os fertilizantes de liberação lenta têm se mostrado como uma excelente alternativa em relação a adubação convencional mineral. Desta forma, objetivou-se avaliar o efeito de diferentes fontes de P no crescimento e produção da pimenta malagueta (Capsicum frutescens L.). Realizou-se um experimento em casa de vegetação no Campus JK da UFVJM, Diamantina -MG, no delineamento inteiramente casualizado com onze tratamentos (ausência de adubação, tratamento mineral, tratamento orgânico e quatro fontes fosfatadas de liberação lenta: organomineral peletizado, organomineral granulado, MAP revestido e formulado triplo, nas doses de 150 e 300 kg ha-1de P2O5). Foram avaliadas variáveis de crescimento, acúmulo de matéria fresca e matéria seca e produtividade aos 180 dias após o transplantio. Os tratamentos organomineral peletizado e granulado 300 kg ha-1de P2O5promoveram os melhores resultados para os parâmetros massa seca do sistema radicular, número total de frutos, massa fresca emassa seca de frutos e produtividade total. Tais resultados podem ser explicados pela melhor eficiência da liberação do P pelos fertilizantes e melhor absorção do nutriente pela planta, tornando-se uma excelente opção em relação as fontes convencionais comumente adotadas.
Subject(s)
Capsicum/growth & development , Capsicum/drug effects , FertilizersABSTRACT
Low inherent nitrogen (N), phosphorus (P), and potassium (K) contents of smallholder farms limit maize grain yield. Maize grain yield response to N, P, and K mineral fertilizer application and economically optimal rates for nitrogen (EORN), phosphorus (EORP), and potassium (EORK) were evaluated on a Ferric Acrisol within the semi-deciduous forest zone of Ghana. The nutrient rates evaluated were N (0, 30, 60, 90, and 120 kg N ha-1), P (0, 30, 60, and 90 kg ha-1 P2O5), and K (0, 30, 60 and 90 kg ha-1 K2O). The treatments were arranged in a randomized complete block with three replications using an incomplete factorial design. Nutrient responses were determined using asymptotic quadratic-plus plateau functions. The best nitrogen rate for all P and K levels was 60 kg ha-1, which gave grain yield of 5 t ha-1 . Nitrogen uptake, N agronomic and N recovery efficiencies peaked at 60 kg N ha-1 while N partial factor productivity declined with increasing N application rate. Cost to grain price ratios (CP) were 1.29, 1.65, and 1.65 for N, P, and K, respectively. The EORN was 61 kg ha-1, 32% less than the recommended 90 kg N ha-1 for maize production in the semi-deciduous forest zone of Ghana. Nitrogen application had the lowest CP ratio, making its application economically profitable than P and K. The findings suggest that the application of N at 61 kg N ha-1 to maize is economically profitable than at higher application rates. However, further studies should be conducted on farmers' fields to validate the results obtained.
ABSTRACT
The objective of this study was to determine the effect of perennial ryegrass (PRG) forages differing in their concentration of water-soluble carbohydrates (WSC) and crude protein (CP), and collected in spring and autumn, on in vitro rumen fermentation variables, nitrogen (N) metabolism indicators and methane (CH4) output, using a batch culture system. Two contrasting PRG pastures, sampled both in autumn and spring, were used: high (HS) and low (LS) sugar pastures with WSC concentrations of 322 and 343 g/kg for HS (autumn and spring), and 224 and 293 g/kg for LS in autumn and spring, respectively. Duplicates were incubated for 24 h with rumen inocula in three different days (blocks). Headspace gas pressure was measured at 2, 3, 4, 5, 6, 8, 10, 12, 18, and 24 h, and CH4 concentration was determined. The supernatants were analysed for individual volatile fatty acids (VFA) concentrations, and NH3-N. The solid residue was analysed for total N and neutral detergent insoluble N. Another set of duplicates was incubated for 4 h for VFA and NH3-N determination. The HS produced more gas (218 vs. 204 mL/g OM), tended to increase total VFA production (52.0 mM vs. 49.5 mM at 24 h), reduced the acetate:propionate ratio (2.52 vs. 3.20 at 4 h and 2.85 vs. 3.19 at 24 h) and CH4 production relative to total gas production (15.6 vs. 16.8 mL/100 mL) and, improved N use efficiency (22.1 vs. 20.9). The contrasting chemical composition modified in vitro rumen fermentation tending to increase total VFA production, reduce the acetate:propionate ratio and CH4 concentration, and improve N use efficiency through lower rumen NH3-N.
ABSTRACT
Urea is the most widely used nitrogen (N) fertilizer, with a projected increase in annual demand of 1.5% in the coming years. After its application to soil, urea undergoes hydrolysis via the urease enzyme, causing increases in the soil pH in the surrounding area of the granules and resulting in NH3 losses that average 16% of N applied worldwide and can reach 40% or more in hot and humid conditions. The use of urease inhibitors is an effective way to reduce NH3 losses. Several compounds act as urease inhibitors, but only N-(n-butyl) thiophosphoric triamide (NBPT) has been used worldwide, being the most successful in a market that has grown 16% per year in the past 10â¯years. Only in the past three years other compounds are being commercially launched. In comparison to urea, NBPT-treated urea reduces NH3 loss by around 53%. Yield gain by NBPT usage is of the order of 6.0% and varies from -0.8 to 10.2% depending on crop species. Nitrification inhibitors usually increase NH3 volatilization and mixing them with urease inhibitors partially offsets the benefits of the latter in reducing NH3 loss. The efficacy of NBPT to reduce NH3 loss is well documented, but there is a need for further improvement to increase the period of inhibition and the shelf life of NBPT-treated urea.
ABSTRACT
Different growth rates of grasses from South American natural grasslands are adaptations to soils of low fertility. Grasses with fast growth rate are species with an accumulation of nutrients in soluble forms, with a high metabolic rate. This work aimed to study whether grasses with different growth rates have different phosphorus (P) uptake and efficiency of P use with high and low P availability in soil, as well as whether phosphatase activity is related to the species growth rate and variations in P biochemical forms in the tissues. Three native grasses (Axonopus affinis, Paspalum notatum, and Andropogon lateralis) were grown in pots with soil. Along plant growth, biomass production and its structural components were measured, as well as leaf acid phosphatase activity and leaf P chemical fractions. At 40 days of growth, leaf acid phosphatase activity declined by about 20-30% with an increase of P availability in soil for A. affinis and P. notatum, respectively. Under both soil P levels, P. notatum showed the highest plant total biomass, leaf dry weight and highest P use efficiency. A. affinis presented the higher P uptake efficiency and soluble organic P concentration in the leaf tissues. A. lateralis showed P-Lipid concentration 1.6 and 1.3 times higher than A. affinis and P. notatum, respectively. In conclusion, acid phosphatase activity in grass of higher growth rate is related to higher remobilization of P due to higher demand, as in A. affinis, and higher growth rates are associated with higher P uptake efficiency.
Subject(s)
Phosphorus , Poaceae , Phosphoric Monoester Hydrolases , SoilABSTRACT
During forest succession, litterfall nutrient fluxes increase significantly. The higher inputs of organic matter and nutrients through litterfall affects positively soil fertility and the species composition, which are essential components in forest restoration and management programs. In the present study, the input of nutrients to the forest soil via litterfall components was estimated for two sites of different development stages, in an early successional alluvial rain forest in Brazil. Litterfall returned to the soil, in kg/ha, ca. 93 N, 79 Ca, 24 K, 15 Mg, 6 P, 1.7 Mn, 0.94 Fe, 0.18 Zn, 0.09 Cu and 11.2 Al, in the site where trees were more abundant and had higher values of basal area. In the other area, where trees where less abundant and values of basal area were comparatively low, litterfall returned <50% of those amounts to the forest soil, except for Al. The amount of Al that returned to the soil was similar in both areas due to the high contribution of Tibouchina pulchra (82% of Al returned). Comparatively, high proportion of three dominant native tree species (Myrsine coriacea, T. pulchra and Cecropia pachystachya) explained better litter nutrient use efficiency (mainly N and P) in the site with the least advanced successional stage. Although litterfall of these species show lower nutrient concentrations than the other tree species, their nutrient fluxes were high in both sites, indicating a certain independence from soil essential nutrients. Such feature of the native species is very advantageous and should be considered in forest restoration programs. Rev. Biol. Trop. 59 (4): 1869-1882. Epub 2011 December 01.
Durante la sucesión secundaria forestal, el flujo de nutrientes en la hojarasca se incrementa significativamente. Los altos ingresos de materia orgánica y nutrientes a través de la hojarasca afecta positivamente la fertilidad del suelo y la composición de especies, las cuales son componentes esenciales para programas de restauración forestal y de manejo. En el presente estudio, el ingreso de nutrientes a través de la hojarasca y sus componentes fueron estimados para dos sitios de una selva lluviosa atlántica aluvial en sucesión temprana. La cantidad anual de elementos que ingresan al suelo desde la vegetación más desarrollada (sitios con alta área basal y abundancia de árboles) fueron (en kg/ha): 93 N, 79 Ca, 24 K, 15 Mg, 6 P, 1.7 Mn, 0.94 Fe, 0.18 Zn, 0.09 Cu y 11.2 Al. Menos de la mitad de esas cantidades fueron aportadas por la vegetación menos desarrollada, excepto para el Al. La cantidad de Al aportada a este sitio fue similar a la contribución de la vegetación más desarrollada, debido a la contribución de: Tibouchina pulchra (82% de todo el Al aportado). La eficiencia en el uso de nutrientes de la hojarasca (principalmente de N y P) de la vegetación menos desarrollada fue superior a la eficiencia de una más desarrollada, debido a la alta proporción de tres especies nativas dominantes (Myrsine coriacea, Tibouchina pulchra y Cecropia pachystachya) en la primera. Si bien la hojarasca de esas especies presenta menor concentración de nutrientes que las otras especies arbóreas, el flujo de nutrientes fue mayor (para ambos sitios), marcando una cierta independencia de los nutrientes esenciales del suelo. Las cantidades de esas especies deberían ser consideradas con mayor atención para su uso en programas de restauración forestal.
Subject(s)
Biodegradation, Environmental , Plant Leaves/metabolism , Soil/chemistry , Trees/metabolism , Brazil , Inorganic Chemicals/analysis , Organic Chemicals/analysis , Time Factors , Tropical Climate , Trees/growth & developmentABSTRACT
La producción de hojarasca, el retorno y la reabsorción de nutrientes, y la eficiencia en su uso, fueron estudiados durante un año en plantaciones de Acacia mangium estable-cidas en suelos degradados por minería aurífera en la región del Bajo Cauca colom-biano. La producción anual de hojarasca fina fue de 10,4 Mg ha-1 y estuvo dominada por la fracción foliar (54%), seguida del material reproductivo (24%), y en menor pro-porción por otros restos (6%) y hojas de otras especies (1,5%). Los mayores retornos de materia orgánica y nutrientes se presentaron en los sitios clasificados como de calidad alta, en tanto que la práctica de subsolado del suelo, previo establecimiento de las plantaciones, no mostró efectos significativos sobre estos. La hojarasca foliar mostró una concentración alta de N y consecuentemente, dados los altos valores de producción de esta fracción, un retorno potencial alto de N. El P, con baja concentración foliar y un bajo retorno potencial, además de los altos valores de los índices de eficiencia en su uso y de reabsorción foliar, fue el nutriente más limitante. Los altos valores de producción de hojarasca fina y de retorno potencial de nutrientes determinados en este es-tudio, muestran que la especie Acacia mangium tiene un gran potencial para la recupera-ción de áreas degradadas, a partir del restablecimiento de los ciclos biogeoquímicos.
Fine litter production, nutrient return, nutrient resorption, and nutrient use efficiency were studied during one year in Acacia mangium forest plantations in mining gold degraded soils at the Bajo Cauca region of Colombia. Annual fine litter production was estimated at 10.4 Mg ha-1 and it was dominated by the leaf fraction (54%), followed by the reproduc-tive material (24%) and to a lesser proportion by other debris (6%) and other species leaves (1.5%). The highest organic matter and nutrients returns were found on sites classified as high quality. Soil plowing realized previous Acacia mangium planting, did not show any significant effect on organic matter and nutrients returns. A. mangium leaf litter had a high N concentration and consequently, given the high leaf litter production values, it was found a high N return. By the opposite, leaf litter P content and P returns via litter fall were very low. The high values found for P retranslocation and P use efficiency indexes showed that P was the most limiting nutrient for the species. The high values of fine litter production and nutrient return via leaf litter indicate that A. mangium has a great capacity for degraded areas reclamation, as of the restoration of the biogeochemical cycles.
ABSTRACT
As leguminosas para adubação verde têm sido introduzidas nos sistemas agrícolas para a recuperação de solos desgastados pelo uso intensivo. O objetivo desse trabalho foi avaliar a resposta de leguminosas herbáceas à aplicação de calcário e fósforo sobre a produção de biomassa e eficiência nutricional para o P, Ca e Mg. O experimento foi desenvolvido em casa-de-vegetação do Departamento de Ciência do Solo da Universidade Federal Rural da Amazônia, utilizando-se um Latossolo Amarelo distrófico coletado na profundidade de 0 - 20 cm, em Belém, PA. O delineamento experimental usado foi o de blocos ao acaso, com arranjo de tratamentos em um fatorial 3³, onde foram comparadas três espécies de leguminosas: mucuna preta (Stizolobium atterrimum), mucuna cochinchinensis (Stilozobium cochinchinensis) e feijão-de-porco (Canavalia ensiformes); três níveis de calagem: de calcário dolomítico (0, 4 e 8 t.ha-1) e de fósforo (0, 25 e 45 mg.dm-3), com quatro repetições cada um. Mucuna cochinchinensis e o feijão de porco produziram maiores quantidades de biomassa vegetal do que a mucuna preta, sendo que a primeira espécie acumulou maior quantidade de P e a segunda maior quantidade de Ca. Mucuna cochinchinensis apresentou maior eficiência de utilização de P, Ca e Mg na ausência da calagem. Nos solos intemperizados com baixa concentração de P, Ca e Mg, o feijão-de-porco e a mucuna cochinchinensis poderão ter melhor desempenho do que a mucuna preta, visto que apresentaram maior eficiência de translocação e de utilização desses nutrientes, respectivamente.
The legumes used for green manure have been introduced in agricultural systems for recovering degraded soils by intensive use. The objective of this work was to evaluate the response of herbaceous legumes to liming and P application on dry matter and its nutritional efficiency. The experiment was developed in greenhouse at the Soil Science Department of the Federal University Agricultural of Amazon (Brazil). Soil used was a dystrophic Yellow Latosol, sampled in the 0 - 20 cm depth. A randomized block experimental design was used with treatments arranged in a factorial 3³, comparing three legume species: velvet bean (Stizolobium atterrimum), "mucuna cochinchinensis" (Stilozobium cochinchinensis) and jack bean (Canavalia ensiformes); three doses of liming (0, 4 and 8 t ha-1 of limestone) and of triple superphosphate (0, 25 and 45 mg P dm-3 of soil), with four replications each one. Results showed that "mucuna cochinchinensis" and jack bean produced higher amounts of dry matter than velvet bean. The first species accumulated higher amount of P and the second species higher amount of Ca in the tissue. The "mucuna cochinchinensis" species showed higher use efficiency of Ca, Mg and P in the absence of liming. The jack bean and mucuna cochinchinensis can have better performance than velvet bean, in weathered soils with low concentration of P, Ca and Mg, since they presented higher translocation efficiency and use of these nutrients, respectively.
Subject(s)
Composting , NutrientsABSTRACT
The legumes used for green manure have been introduced in agricultural systems for recovering degraded soils by intensive use. The objective of this work was to evaluate the response of herbaceous legumes to liming and P application on dry matter and its nutritional efficiency. The experiment was developed in greenhouse at the Soil Science Department of the Federal University Agricultural of Amazon (Brazil). Soil used was a dystrophic Yellow Latosol, sampled in the 0 - 20 cm depth. A randomized block experimental design was used with treatments arranged in a factorial 3³, comparing three legume species: velvet bean (Stizolobium atterrimum), "mucuna cochinchinensis" (Stilozobium cochinchinensis) and jack bean (Canavalia ensiformes); three doses of liming (0, 4 and 8 t ha-1 of limestone) and of triple superphosphate (0, 25 and 45 mg P dm-3 of soil), with four replications each one. Results showed that "mucuna cochinchinensis" and jack bean produced higher amounts of dry matter than velvet bean. The first species accumulated higher amount of P and the second species higher amount of Ca in the tissue. The "mucuna cochinchinensis" species showed higher use efficiency of Ca, Mg and P in the absence of liming. The jack bean and mucuna cochinchinensis can have better performance than velvet bean, in weathered soils with low concentration of P, Ca and Mg, since they presented higher translocation efficiency and use of these nutrients, respectively.
As leguminosas para adubação verde têm sido introduzidas nos sistemas agrícolas para a recuperação de solos desgastados pelo uso intensivo. O objetivo desse trabalho foi avaliar a resposta de leguminosas herbáceas à aplicação de calcário e fósforo sobre a produção de biomassa e eficiência nutricional para o P, Ca e Mg. O experimento foi desenvolvido em casa-de-vegetação do Departamento de Ciência do Solo da Universidade Federal Rural da Amazônia, utilizando-se um Latossolo Amarelo distrófico coletado na profundidade de 0 - 20 cm, em Belém, PA. O delineamento experimental usado foi o de blocos ao acaso, com arranjo de tratamentos em um fatorial 3³, onde foram comparadas três espécies de leguminosas: mucuna preta (Stizolobium atterrimum), mucuna cochinchinensis (Stilozobium cochinchinensis) e feijão-de-porco (Canavalia ensiformes); três níveis de calagem: de calcário dolomítico (0, 4 e 8 t.ha-1) e de fósforo (0, 25 e 45 mg.dm-3), com quatro repetições cada um. Mucuna cochinchinensis e o feijão de porco produziram maiores quantidades de biomassa vegetal do que a mucuna preta, sendo que a primeira espécie acumulou maior quantidade de P e a segunda maior quantidade de Ca. Mucuna cochinchinensis apresentou maior eficiência de utilização de P, Ca e Mg na ausência da calagem. Nos solos intemperizados com baixa concentração de P, Ca e Mg, o feijão-de-porco e a mucuna cochinchinensis poderão ter melhor desempenho do que a mucuna preta, visto que apresentaram maior eficiência de translocação e de utilização desses nutrientes, respectivamente.
ABSTRACT
Seedlings of nine southern Chilean trees were grown at three nutrient supply rates, to examine the roles of growth rate, biomass distribution and nutrient use traits in determining species natural distributions on resource gradients. Relative growth rate (RGR) showed no overall relationship with species site requirements, although RGR of fertile-site species tended to be more responsive to nutrient supply. In the low-nutrient treatment, infertility-tolerant Fitzroya cupressoides showed a higher RGR rank than a fertility-demanding species (Laurelia philippiana) which outgrew it substantially at the highest supply rate. This reversal of RGR ranks was associated with divergent nutrient use responses: at high nutrient supply both spp. had similar plant nitrogen concentrations (PNC), whereas at the low supply rate Fitzroya's production of biomass per unit of assimilated N was twice that of Laurelia's. However, this pattern does not appear to serve as a general explanation of the respective distributions of the study species, as RGR ranks of most species were unaltered by nutrient supply. At low nutrient availability, no clear differences in shoot:root ratio (SRR) were apparent between poor-site and fertile-site species. However, at high nutrient availability, SRR was markedly higher in the latter, resulting from differences in biomass allocation to stems (not leaves). Leaf area ratios (LAR) were higher in fertile-site species than in those tolerant of low fertility, because of differences in specific leaf area rather than leaf weight ratio. Very high LAR at high nutrient supply was characteristic of most shade-tolerant angiosperms, but not of shade-tolerant conifers. Although PNC showed no overall differences between poor- and fertile-site species, sensitivity of PNC to external supply rate was greatest in two infertility-tolerant conifers. In contrast, the angiosperm Weinmannia trichosperma, although tolerant of low fertility, responded to increased nutrient supply with greatly increased RGR and little change in PNC. Results show little trait convergence between conifers and angiosperms in adaptation both to shade and to infertile soils; i.e. fitness of different taxa in a given environment may hinge on different trait combinations.
ABSTRACT
We investigated plant ecophysiological response to fertilization of selected sites along an elevation gradient in a pinyon-juniper woodland. Plant density and species composition followed typical patterns for pinyon-juniper woodlands over this gradient, with a sparse juniper (Juniperus monosperma (Engelm.) Sarg.)-grassland community at the lowest elevation and gradually increasing total canopy cover and pinyon (Pinus edulis Engelm.) cover with elevation. Carbon isotope analysis showed that both tree species had higher water-use efficiency (WUE) at the lowest, and presumably driest, sites. Over most of the gradient, however, it appeared that changes in stand density compensated for changes in water availability. Contrary to initial hypotheses, the more drought-tolerant juniper did not demonstrate significantly greater WUE than pinyon, although it maintained positive carbon gain at lower predawn xylem pressure potentials than pinyon. In pinyon, both A max and WUE increased with increasing N concentration in tissues. Pinyon needles also demonstrated declining nitrogen-use efficiency with age. There was no relationship between tissue N and either A max or WUE measured at A max in juniper, although δ13C analysis indicated that WUE increased in juniper with increased N availability. Results from this study suggest that plasticity in plant physiological processes could result in nonlinear responses of organic matter production to climate change, and therefore must be accounted for in ecosystem models.