Influence of parent material on soil chemical characteristics in a semi-arid tropical region of Northeast Brazil.

Soil parental material is one of the main factors that influence pedogenesis. Several studies evaluated the relationship between the parent material and soil chemistry, but few studies have assessed such a relationship in semi-arid tropical regions. This investigation was carried out to assess the effect of different parent materials on the chemical composition and available concentrations of macronutrients and micronutrients, including potentially toxic elements (Cd, Cr, Ni, and Pb) in soils in a semi-arid tropical setting. The chemical composition of the soils inherited the geochemical signature of their parent materials. Quartz sandstones, augen gneisses, and peraluminous granites exhibited the lowest reservoirs of plant nutrients and formed sandy, acid, and infertile soils. On the other hand, alkaline soils and soils with high concentrations of nutrients formed on ultramafic rocks (harzburgite), marble, and anorthosite. The pH, clay content, and CEC were the main attributes of the soils governing the availability of macro and micronutrients. The low soil organic carbon contents did not influence the availability of the nutrients. The parent material also influenced the soil texture. Parent materials that are richer in silica formed more sandy soils. The availability of Cd, Cr, and Pb in soils was low; however, the elevated Ni concentrations of soils derived from ultramafic rocks may pose risks to the environment and human health. Cluster and discriminant analyses were used to discriminate the natural fertility of soils. These results are useful for the agro-pedological zoning of the Brazilian semi-arid tropical region and for land use planning.

Combining geospatial analyses to optimize quality reference values of rare earth elements in soils.

High pedological and geological variability can trigger the formation of REE hotspots, causing a need to optimize the establishment of quality reference values (QRVs). Thus, we determined the background concentrations of REEs in the soils of an emerging Brazilian state and used a combination of Moran's I and indicator kriging to identify REE hotspots and determine QRVs. A total of 100 composite soil samples was collected at a 0.20 m depth to establish background concentrations, QRVs, and spatial distribution and to elaborate probability maps for REEs. The QRVs established for soils were the following (mg kg-1): La (27.21), Ce (57.26), Pr (10.49), Nd (24.29), Sm (4.75), Eu (0.90), Gd (4.22), Tb (0.82), Dy (1.54), Ho (0.38), Er (1.23), Yb (1.07), Lu (0.24), Y (10.65), and Sc (3.70). It was possible to draw attention to the Northwest and Southwest regions of the Rio Grande do Norte (RN) state, due to the formation of REE hotspots, indicated by Moran's I, and a high tendency to exceed the QRVs, confirmed by the indicator kriging. The high background concentrations and geochemical patterns for REEs showed that a single QRV for each REE and the entire state can neglect specific environmental characteristics and misrepresent the natural geochemistry of the soil. Thus, specific QRVs were established to optimize the monitoring of natural REE values by identifying hotspot areas. The criteria established here may be useful for other groups of potentially toxic elements, provided that observations meet the requirements of the spatial autocorrelation and kriging analyses. Graphical abstract.

Natural concentrations and reference values for trace elements in soils of a tropical volcanic archipelago.

Fernando de Noronha is a small volcanic archipelago in the Southern Atlantic, some 350 km NE of the city of Natal in NE Brazil. These remote volcanic islands represent a largely pristine environment, distant from sources of anthropogenic contamination. This study was carried out to determine the natural concentrations of Ag, Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, Sb, V and Zn in the A and B horizons of soils of Fernando de Noronha. The aims of the study were twofold: determine whether there is a relationship between the bedrock geology and soils and to establish quality reference values for soils from Fernando de Noronha. Soil samples were subjected to acid digestion by the USEPA method 3051A, and metals were determined by inductively coupled plasma emission spectrophotometry. The results showed that the trace element distribution largely reflects the geochemistry of the underlying volcanic rocks of the Remedios and Quixaba Formations. The results demonstrate that the concentrations of Ba, Cr, Zn, Ni and Cu from the soils of the volcanic Fernando de Noronha archipelago are higher than those found in soils from continental Brazil. However, concentrations of Ni, Cu and Co are lower in soils of the archipelago as compared to other volcanic islands throughout the world. The elevated trace element concentrations of the volcanic parent material of Fernando de Noronha soils seem to be the main factor governing the relatively high natural concentrations of trace elements.

Improving rock phosphate availability through feeding, mixing and processing with composting manure.

The objective of this study was to improve the availability of phosphorus (P) from rock phosphate (RP) through feeding, mixing and composting manure. The experiment was conducted as a 3 x 2 split-plot design. Manure was collected from 12 Boran steers (200+/-4.5 kg live weight) fed a basal diet of Napier grass (Pennisetum purpureum) at 2.5% body weight on a dry matter (DM) basis. The main plot treatments were (i) manure from steers supplemented with 113 g Busumbu rock phosphate (BRP) per day (FBRP), (ii) manure from steers not supplemented with BRP, feces mixed with 113 g BRP per day (MBRP) and (iii) manure from steers not supplemented with BRP and feces not mixed with BRP (CONT). The sub-plots comprised composting the manure either (i) mixed with 440 g of wheat (Triticum aestivum L.) straw per kg fresh feces (WS) or (ii) without straw (WOS). The manure was composted in 200 L plastic bins for 90 days. After 90 days, P availability was evaluated (i) by aerobic laboratory incubation at 25 degrees C for 1, 2, 4, 8, 12, and 16 weeks and (ii) by greenhouse agronomic evaluation study using maize (Zea Mays L.) as the test crop in either a humic Nitosol or an Andosol. In the laboratory incubation study, resin P was higher (p<0.05) for the WS compost than for the WOS compost; values were higher (p<0.05) for the Andosol than for Nitosol and followed the order of FBRP-WS, Andosol>FBRP-WS, Nitosol>MBRP-WS, Andosol>MBRP-WS, Nitosol>FBRP-WOS, Andosol>FBRP-WOS, Nitosol. In the greenhouse evaluation, maize crops in the WS compost had higher (p<0.05) biomass yield than the reference fertilizer, triple super phosphate, (173% versus 196%; Andosol and Nitosol, respectively). The biomass yield and P uptake relative agronomic effectiveness (RAE) for WS compost was also higher (p<0.05) than that of WOS compost (184 versus 3+/-0.8 and 242 versus 162+/-0.2, WS and WOS, biomass yield and P uptake, respectively). Nitosol biomass yield and P uptake RAE were also higher (p<0.05) than for the Andosol (99 versus 88+/-0.8 and 332 versus 72+/-0.2, Nitosol and Andosol, biomass yield and P uptake, respectively). The results show that P-enriched composting in the presence of wheat straw significantly increased P availability and increased plant growth. However, in terms of plant growth, there was no additional benefit of first feeding the RP to steers before composting the manure because most of the RP fed seem to have been utilized by the animal.

Farming with rocks and minerals: challenges and opportunities.

In many parts of the world food security is at risk. One of the biophysical root causes of falling per-capita food production is the declining quality and quantity of soils. To reverse this trend and increase soil fertility soil and plant nutrients have to be replenished. This review provides a literature survey of experiences of using multi-nutrient rock fertilizers for soil fertility enhancement from temperate and tropical environments. Advantages and limitations of the application of rock fertilizers are discussed. Examples are provided from two successful nutrient replenishment projects in Africa where locally available rock fertilizers are used on highly leached acid soils. The potential of combining organic materials alongside rock fertilizers in soil fertility replenishment strategies is stressed.

Potential of East African phosphate rock deposits in integrated nutrient management strategies.

Phosphorus deficiency affects around 80% of the acid soils of western Kenya, but fertilizer use is limited due to high prices. This paper explores the potential of local phosphate rocks (PR) as a remedy within the context on an integrated soil fertility management approach. A promising phosphate rock is Minjingu PR (MPR, Tanzania), a sedimentary/biogenic deposit which contains about 13% total P and 3% neutral ammonium citrate (NAC) soluble P. On-farm trials in P-deficient soils in western Kenya demonstrate MPR to be as effective as triple superphosphate (TSP, 20% P) at equal P rates. The benefits are most pronounced with the integration of agroforestry technologies that improve soil fertility. Besides Minjingu PR, Busumbu PR from Uganda (BPR) is potentially another source of P. It is typical of the abundant but unreactive igneous PRs in eastern, central and southern Africa. Agronomic performance of BPR is poorer, though its lower cost and location near to P-deficient areas in western Kenya make it attractive in some situations. The policy implications of these findings are discussed further in the paper.

Farming with rocks and minerals: challenges and opportunities

In many parts of the world food security is at risk. One of the biophysical root causes of falling per-capita food production is the declining quality and quantity of soils. To reverse this trend and increase soil fertility soil and plant nutrients have to be replenished. This review provides a literature survey of experiences of using multi-nutrient rock fertilizers for soil fertility enhancement from temperate and tropical environments. Advantages and limitations of the application of rock fertilizers are discussed. Examples are provided from two successful nutrient replenishment projects in Africa where locally available rock fertilizers are used on highly leached acid soils. The potential of combining organic materials alongside rock fertilizers in soil fertility replenishment strategies is stressed.

Em muitas partes do mundo a segurança alimentar está em risco. A raiz de uma das causas biofísicas da queda da produção alimentar per capita é o declínio da qualidade e quantidade de solos. Para reverter essa tendência e aumentar a fertilidade, ambos solo e nutrientes para as plantas precisam ser repostos. Este artigo aborda uma pesquisa bibliográfica de experiências na utilização de rochagem com multi-nutrientes para intensificação da fertilização do solo em ambientes temperados e tropicais. As vantagens e as limitações na aplicação de pó de rocha são discutidas. São apresentados dois projetos bem sucedidos de substituição de nutrientes na Africa, onde as rochas disponíveis no local são utilizados em solos ácidos altamente lixiviados. É enfatizado o potencial da combinação de materiais orgânicos juntamente com pó de rocha nas estratégias de reposição da fertilidade dos solos.

Potential of East African phosphate rock deposits in integrated nutrient management strategies

Phosphorus deficiency affects around 80 percent of the acid soils of western Kenya, but fertilizer use is limited due to high prices. This paper explores the potential of local phosphate rocks (PR) as a remedy within the context on an integrated soil fertility management approach. A promising phosphate rock is Minjingu PR (MPR, Tanzania), a sedimentary/biogenic deposit which contains about 13 percent total P and 3 percent neutral ammonium citrate (NAC) soluble P. On-farm trials in P-deficient soils in western Kenya demonstrate MPR to be as effective as triple superphosphate (TSP, 20 percent P) at equal P rates. The benefits are most pronounced with the integration of agroforestry technologies that improve soil fertility. Besides Minjingu PR, Busumbu PR from Uganda (BPR) is potentially another source of P. It is typical of the abundant but unreactive igneous PRs in eastern, central and southern Africa. Agronomic performance of BPR is poorer, though its lower cost and location near to P-deficient areas in western Kenya make it attractive in some situations. The policy implications of these findings are discussed further in the paper.

A deficiência de fósforo afeta em torno de 80 por cento dos solos ácidos do Quênia ocidental, mas o uso de fertilizantes é limitado devido aos preços altos. Este artigo explora o potencial das rochas fosfáticas locais (PR) como regenerador da fertilidade dos solos dentro do contexto de uma abordagem de gestão integrada. Uma rocha fosfática promissora é a Minjingu PR (MPR, Tanzânia), um depósito sedimentar/biogênico que contém por volta de13 por cento total P e 3 por cento citrato neutro de amônia (NAC) P solúvel. Testes em fazendas agrícolas com solos deficientes em P no Quênia ocidental demonstram que a MPR é tão efetiva quanto o superfosfato triplo (TSP, 20 por cento P) na mesma proporção de P. Os benefícios são mais pronunciados com a integração das tecnologias agroflorestais que melhoram a fertilidade do solo. Da mesma forma que o Minjingu PR, Busumbu PR de Uganda (BPR) é outra fonte potencial de P. É típica do abundante, porém não-reativo complexo ígneo PRs do leste, centro e sul da Africa. A performance agronômica de BPR é inferior ainda que tenha custo mais baixo e localização próxima às áreas deficientes de P no Quênia ocidental, tornando-se mais atrativo em algumas situações. As implicações políticas dessas descobertas são discutidas mais adiante neste artigo.