12 research outputs found
Enhancing Carbon Sequestration in Mediterranean Agroforestry Systems: A Review
ReviewThe agroforestry systems with a high potential for C sequestration are those degraded by
poor management strategies. Studies on changes in soil C status in these ecosystems mostly take
into account labile C pools. Labile and stable soil organic matter (SOM) fractions are affected by
soil management and land-use changes. Stable C pools are essential to understanding effects of
land-use on soil C storage in the long term. The SOM stability is partly enhanced by the interaction
of SOM with minerals and its inclusion into soil aggregates. Recalcitrant substances (e.g., lignin and
chitin) also contribute to the passive SOM fraction. Macroaggregates mostly reflect the influence of
plant roots and coarse intra-aggregate particulate SOM (POM), whereas microaggregates reflect the
influence of fine interaggregate POM, clay concentration and humified SOM fraction. Often, POM
is more sensitive to soil management changes than total SOM. Glomalin is a recalcitrant protein
consisting of chitin produced by mycorrhizal fungi to protect hyphae. Glomalin has implications
on C sequestration in agroforestry soils, but further research is needed before any prediction can be
made. One challenge is reducing the CO2 emission from roots, and increasing the recalcitrant root Cinfo:eu-repo/semantics/publishedVersio
Nitrogen distribution, remobilization and re-cycling in young orchard of non-bearing Rocha pear trees
In newly planted orchards, special attention must be paid to fertilization to build up the permanent
structure of the trees so that high yield and fruit quality can be reached later on. Nitrogen (N) plays a
major role in the fertilization plan, although few studies have assessed its use efficiency in young nonbearing
trees, especially in field conditions. In this work, 1â3 years old âRochaâ pear trees, grafted on
quince BA29, were planted in a Mediterranean region, and fertigated with 6 g N tree 1 year 1 as
ammonium nitrate with 5 at.% 15N enrichment to study the fertilizer N uptake during the vegetative
cycle, the overall fertilizer N use efficiency at the end of each year, and the plantâsoil N balance for this
period. Nitrogen remobilization and the re-cycling of N from senescent leaves were also studied by
fertilizing some pear trees with 10 at.% 15N enrichment.
Nitrogen uptake was minimum at bud break and peaked in June/July remainingmore or less constant
until leaf fall. About 25% of the fertilizer N taken up by 3 years old trees in the previous year was found in
the new tissues formed (flowers, leaves and 1-year-old shoots), reaching 27% when fine roots were also
included. In those trees, 32% and 54% of the 15N stored in the previous year in the trunk and older shoots,
respectively, were mobilized to the new growth in the following year.
Fertilizer N use efficiency by trees increased from the first to the third year but was generally small
(6%, 14% and 33%), and estimated N losses were large (89%, 46% and 53%, respectively in the first, second
and third years). Irrigation water and soil provided more N to the trees than fertilizer N
Underestimated role of legume roots for soil N fertility
Research ArticleNitrogen (N) is a major fertilizing element for plants.
The distribution of N in legumes is influencing the efficiency of
the next crop. Nitrogen storage in legumes is actually estimated
by N fixation in shoots, whereas there is little knowledge on the
contribution of roots and nodules to legume N and soil N. Here,
we studied the contribution of roots and nodules of grain and
pasture legumes to plant N and soil N in Mediterranean fields.
Experiments were run under rainfed conditions for a 2-year
period in three regions of Portugal. Entire plants including top
plant and visible roots and nodules were sampled at the end of
the growing seasons for grain legumes, sweet and yellow lupine,
and over two harvests in case of pastures. N2 fixation was measured
for grain legumes and pasture legumes using 15N tracing.
Our results show that aboveground N concentration did not vary
among legumes, but differed in the belowground tissues. Field
studies show that 7â11%of total legume N was associated with
roots and nodules. Data also show an allocation of 11â 14 kg N fixed tâ1 belowground dry matter in indeterminate
legumes, which represents half the amount of total aboveground
plant. This finding demonstrates that investigation relying only
on shoot Nunderestimates the role of legumes for soil N fertilityinfo:eu-repo/semantics/publishedVersio
Impact of application of urea modes and rates on yield and nitrous oxide emissions in grapevine (Vitis vinifera L.) on sandy soils in subtropical climate
Grapevines subjected to applications of nitrogen (N) doses on the soil surface can use only a small amount of the nutrient, probably because of losses, such as nitrous oxide (N2O) emissions to the atmosphere. An alternative to reduce these N losses may be the application of N via fertigation. The study aimed to evaluate the N2O emissions and grape yield (Vitis vinifera L.), in grapevines submitted to the application of modes and doses of N cultivated in sandy soil in a subtropical climate. 'Alicante Bouschet' grapevines were subjected to a factorial scheme with three N rates: 0, 40 and 80 kg N ha-1 year-1; and two application modes: surface (NS) and via fertigation (NF). Evaluations of N2O emissions and ammonium (NH4+) and nitrate (NO3-) contents in the soil, N concentration in leaves, grape yield, and number of clusters per plant were carried out. Grapevines cultivated with applications of 40 and 80 kg N ha-1 yr-1, in NF and NS modes, respectively, present-ed higher N2O emissions. N2O emission peaks occurred in the first 9 days after N application. Cumulative N2O emissions ranged from 161.74 ± 34.67 to 496.18 ± 37.00 g ha-1 of N2O-N, in soils that received 0 and 40 kg N ha-1 yr-1, respectively, both in NF mode. Accumulated N2O emissions had a linearly positive relation with the mineral N content in the soil (NH4+ and NO3-) and these had a negative relation with grape yield.
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Nitrogen Transfer from Cover Crop Residues to Onion Grown under Minimum Tillage in Southern Brazil
Nitrogen Nutrition of Fruit Trees to Reconcile Productivity and Environmental Concerns
Although perennial fruit crops represent 1% of global agricultural land, they are of a great economic importance in world trade and in the economy of many regions. The perennial woody nature of fruit trees, their physiological stages of growth, the root distribution pattern, and the presence of herbaceous vegetation in alleys make orchard systems efficient in the use and recycling of nitrogen (N). The present paper intends to review the existing literature on N nutrition of young and mature deciduous and evergreen fruit trees with special emphasis to temperate and Mediterranean climates. There are two major sources of N contributing to vegetative tree growth and reproduction: root N uptake and internal N cycling. Optimisation of the use of external and internal N sources is important for a sustainable fruit production, as N use efficiency by young and mature fruit trees is generally lower than 55% and losses of fertilizer N may occur with the consequent economic and environmental concern. Organic alternatives to mineral N fertilizer like the application of manure, compost, mulching, and cover crops are scarcely used in perennial fruit trees, in spite of the fact that societyâs expectations call for more sustainable production techniques and the demand for organic fruits is increasing
Avaliacao de alguns processos do ciclo do azoto em solos Portugueses, designadamente atraves do marcador 15N
It is necessary to obtain more detailed information on the processes involved in the N cycle of the soil-plant system. Thus, the fixing ability of several legumes was quantified and the N balance on Winter wheat, at Elves (Portugal) was evaluated, using "1"5#NU# isotope. Fababeans presented the highest fixing capacity (53 - 90% N derived from the fertilizer N dfa), even without inoculation, and under drought stress. Chickpea also showed a high fixing rate (44-80% N dfa), but total N_2 fixed was low (20 Kg N ha"-"1). Symbiosis with peas was depressed by water deficit and by Mo deficiency. Under favourable conditions, fixation rate reached 88%. Soybeans and green showed low fixation rates, probably due to inefficient rhizobium strains and/or inadequate plant genotypes. Sub clover mixed with non-legumes fixed 50% of its N in the above ground plant material, but no significant N transfer was observed to the non-legumes. The fertilizer use efficiency by Winter wheat was 19% - 44%. The fertilizer N recovered in the soil varied from 15% to 66%. Unaccounted N reached a maximum value of 55% of the applied N. Leaching of NO_3_- was the main loss, but denitrification and volatilization also occurredAvailable from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1200 Lisboa / FCT - Fundação para o CiĂȘncia e a TecnologiaSIGLEPTPortuga
Yield Prediction Models for âRoyal Galaâ and âFuji Supremaâ Apple Varieties Cultivated under a Subtropical Climate
Nitrogen (N) effect on crop yield depends on several factors such as soil type, climatic characteristics and orchard management, including plant density and N fertilization. These variables can be used to develop yield prediction models, which are scarce in the horticulture sector. This study aimed to evaluate the effect of nitrogen fertilization, orchards and cultivars and to predict the yields of âRoyal Galaâ and âFuji Supremaâ apples cultivated in a subtropical climate under different soil N availabilities. During the four seasons, nitrogen fertilization was applied a rates of 0, 25, 50, 100 and 150 kg N haâ1 yearâ1 for âRoyal Galaâ and âFuji Supremaâ apples located in southern Brazil. Yield, average fruit weight and leaf and fruit pulp N concentration were evaluated. Yield prediction models were developed based on the following variables: concentration of N in leaves and fruits, air temperature, chilling units, relative humidity and rainfall. âCultivarâ was the variable responsible for the greatest variation of yield, followed by âyears/seasonâ, and then the âorchard management. The N rates applied in the four seasons did not predict crop yield. In the model, âorchardâ was the greatest determinant for leaf N concentration, and âseasonâ was the main determinant for fruit-pulp N concentration. Mathematical model (3), based on leaf and fruit pulp N concentration, and certain climatic variables (minimum air temperature, annual rainfall and chilling hours < 7.2 °C) had the greatest potential for predicting yield in orchards of âRoyal Galaâ and âFuji Supremaâ
Effect of Elevated Carbon Dioxide Concentration on Rice Quality: Proximate Composition, Dietary Fibers, and Free Sugars
Nitrogen Transfer from Cover Crop Residues to Onion Grown under Minimum Tillage in Southern Brazil
<div><p>ABSTRACT Nitrogen derived from cover crop residues may contribute to the nutrition of onion grown under minimum tillage (MT) and cultivated in rotation. The aim of this study was to evaluate the N transferred from different cover crop residues to the onion crop cultivated under MT in southern Brazil. In June 2014, oilseed radish, black oat, and oilseed radish + black oat residues labeled with 15N were deposited on the soil surface before transplanting onions. During the growth season and at harvest, young expanded onion leaves, complete plants, and samples from different soil layers were collected and analyzed for recovery of 15N-labeled residue. Oilseed radish decomposed faster than other residues and 4 % of residue N was recovered in leaves and bulbs at harvest, but in general, N in plant organs was derived from sources other than the cover crop residues. In addition, leaf N was in the proper range for all treatments and was adequately mobilized to the bases for bulbing. The N derived from decomposing residues contributed little to onion development and the use of these plants should be chosen based on their advantages for physical and biological soil quality.</p></div