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Using agricultural gypsum promotes nutrient descent and generates a less aggressive environment for roots, favoring their development and better use of water and nutrients. However, studies on apple trees are scarce, and there is no official recommendation for gypsum application in the soils of southern Brazil. This work aimed to evaluate the potential use of agricultural gypsum to increase soil fertility and apple tree productivity. The research was carried out in the municipality of Ipê, RS, in an apple orchard cv. Condessa planted fifteen years ago and with acidity in the soil layer of 20-40 cm. The design of the experiment was consisted of randomized blocks, containing five treatments and four replications, with 80 m² each. The treatments consisted of five doses of agricultural gypsum, applied at the beginning of the productive cycle. The study evaluated soil chemical parameters at 0-20 cm and 20-40 cm, chlorophyll content, and crop productivity. The results showed an increase in the sulfur content up to the gypsum dose of 6.0 t⋅ha-1 and a reduction in the magnesium content in the soil at both evaluated depths. Agricultural gypsum application did not significantly influence the other chemical parameters evaluated. Chlorophyll content in apple leaves was reduced, and there was an increase in productivity with the increase in the dose of agricultural gypsum. Therefore, gypsum can potentially improve soil fertility and increase apple tree productivity. [ABSTRACT FROM AUTHOR]

The relationship between growth, yield and climate variables using multivariate analysis on agroforestry system has not been documented yet. Considering the potential of agroforestry systems as strategy to improve the balance of crop production and environmental health, the aims of this study were (i) to analyze the canonical correlations among groups of tree growth and climatic variables during four seasons of the year; and (ii) to characterize the relationships between sugarcane growth, yield, and quality variables in two agroforestry arrangements and sugarcane monocropping system. A field experiment was conducted from September 2011 to June 2016. The information generated in this study is relevant, as it provides information to farmers and can assist in the planning of new agroforestry systems due to the better knowledge of tree–crop interactions and climate effects in Southern Brazil. In this study, we demonstrated that crops and trees interact dynamically as a result of variations in the interception of solar radiation by trees in time due to the effect of tree age and arrangement, and we concluded that larger tree arrangements are suggested to benefit sugarcane growth and yield in agroforestry systems in Southern Brazil. [ABSTRACT FROM AUTHOR]

Ralstonia solanacearum sensu lato causes bacterial wilt in many agronomic crops and tree species economically important worldwide. It is a species complex that has been divided into phylotypes and sequevars, commonly related to geographic distribution. Knowledge of the phylotype composition and genetic variability in populations of this phytopathogenic bacterium is useful for implementing effective control measures. In a survey conducted in 2019, six bacterial strains were obtained from wilted Eucalyptus urophylla trees in plantations located in the municipality of Dom Eliseu, Pará state, Brazil. Multiplex PCR based on the internal transcribed spacer (ITS) indicated that the bacterial strains belonged to two different species, namely R. pseudosolanacearum (phylotype I) and R. solanacearum (phylotype II). In a phylogenetic analysis, the nucleotide sequence of the endoglucanase (egl) gene from eucalypt strains of phylotype I clustered together with sequevar 18 sequences from GenBank. Separation of the strains into two different species was confirmed by repetitive element palindromic PCR (rep‐PCR). Pathogenicity tests demonstrated that the R. solanacearum and R. pseudosolanacearum strains recovered from E. urophylla cause disease in both tomato and eucalypt plants. Until now, only R. solanacearum (Phylotype II) has been reported causing wilt symptoms on Eucalyptus spp. in Brazil. Therefore, the presence of R. pseudosolanacearum and a need for better understanding of its genetic and aggressiveness variability as well as possible differences between the two species should be considered in breeding programmes aimed at the deployment of host resistance. [ABSTRACT FROM AUTHOR]

Site-specific management strategies are usually dependant on the understanding of the underlying cause and effect relationships that occur at the within-field level. The assessment of canopy geometry of tree crops has been facilitated in recent years through the development of light detection and ranging sensors mounted on terrestrial platforms. The main objective of this study was to uncover the factors driving orange tree variability in commercial orange groves. Secondly, this study sought to investigate whether tree geometry information derived from a terrestrial sensing platform is useful information to guide management zones delineation in such groves. A database of soil physical attributes, elevation, historical yield and canopy geometry (canopy volume and height) was analysed in three commercial orange groves in São Paulo, Brazil. Canopy geometry and historical yield were correlated with soil attributes in two of the three groves evaluated; in these groves, the correlation coefficient between yield and soil/landscape information was often above 0.6, depending on the year. Zones of different tree sizes presented different historical yield and soil properties in all three groves. In conclusion, assessing canopy volume provides useful information to delineate management zones and guide enhanced site-specific management strategies. [ABSTRACT FROM AUTHOR]

Characterizing crop spatial variability is crucial for estimating the opportunities for site-specific management practices. In the context of tree crops, ranging sensor technology has been developed to assess tree canopy geometry and control real-time variable rate application of plant protection products and fertilizers. The objective of this study was to characterize the variability of canopy geometry attributes in commercial orange groves in Brazil and therefore estimate the potential impact of sensor-based site-specific management. Using a mobile terrestrial laser scanner, canopy volume and canopy height were measured in 0.25 m length transversal sections along the rows across five large scale commercial orange groves in São Paulo, Brazil. The coefficient of variation of canopy volume ranged from 30 to 40%. Canopy height was less variable, but closely related to canopy volume. Histograms of canopy volume and height were usually negatively skewed indicating regions of the groves with smaller plants and punctual plant resets. In scenarios where input application rates followed canopy volume variability, input savings were around 40% compared to constant rates based on the maximum canopy volume. Maps of canopy geometry derived from mobile terrestrial laser scanning revealed significant canopy spatial variability, suggesting that the groves would benefit from strategies based on management zones and other forms of site-specific management. [ABSTRACT FROM AUTHOR]

The study presented here consisted of an extensive literature investigation on the long term silvicultural experiments of Curua Una research station in the state of Para, Brazil. The objective of the work was to assess the long term ecological and financial sustainability of a set of silvicultural treatments by using numerical figures derived from the literature related to the financial and ecological impacts of the different treatments in the scale of calendar decades. There were 5 treatments including undisturbed forest (control). The remaining four where in two categories. The first included measures to increase natural regeneration of commercial species prior to exploitation. The second included measures aimed at increasing stocking of commercials after exploitation. Adequate data was found to assess the short term success rate of all 5 treatments in terms of achieving adequate stocking of commercial tree species in sizes of trees ≤5 cm dbh in the first few years after initiation. It was also possible to assess tree species community composition, structure and timber financial value for trees ≥5 cm dbh for a period of 15 years following initial treatment for one and for 36 years after initial treatment for two others. The measures used where the stocking index (S.I.) and the establishment factor (E.F.) for the early results and the Shannon-Weinner species diversity index, total % volume of commercial tree species (TPCTV), total volume of potentially commercial tree species (TPTV), harvestable volume in the year 1993 (HV), number of stems ha-1 (STD) and stand basal area in m² ha-1. Results showed that overall silvicultural systems that included post exploitation treatments where generally more sustainable in terms of long term biodiversity value and more financially profitable relative to systems which relied on post exploitation treatments. These results suggest that drastic revision of current legislation must take place in nations with Amazonian forest because these currently include only post exploitation silvicultural treatments. [ABSTRACT FROM AUTHOR]

We analyze changes in the extent of slash and burn cultivation (SBC) and shifting cultivation (SC) and the main drivers of change observed in the last 10 years across the Brazilian Amazon. Our results show that SC is stable in indigenous andcaboclocommunities from Amazonas and Acre. SBC increases along new roads, illustrating how roads shape deforestation frontiers beyond the “arc of deforestation.” In established forest frontiers, the conversion of forests into pasture or cash crops through SBC continues to increase locally, but smallholders' diversification strategies translate into complex land uses with both the increase and decrease of SBC and SC observed locally. Secure land tenure, access to markets, and population increase appear to be driving to the classic intensification path. Overall, access to cash transfer programs has helped stabilize forest frontiers as households become less reliant on subsistence agricultural production. [ABSTRACT FROM PUBLISHER]