Interaction soil compaction and soil moisture in physiological responses of freshly planted coffee

In the field, coffee is subject to the stress of soil compaction and lack of water, which may cause changes in the physiological responses of the plant. The objective of this study was to evaluate the physiological responses of the coffee tree under different soil moisture content and compaction degrees in the soil subsurface. The experimental design was in blocks, arranged in a factorial scheme, with four replications. The first factor corresponds to the two wetlands, 50 and 100% of the soil field capacity. The second factor corresponds to 60, 70, 80 and 90% of soil subsurface compaction. The experimental plot consisted of a Coffea arabica L. plant grown on a polyvinyl chloride column. The physiological responses were evaluated at 180 days of planting. The photosynthetic rate, carbon consumption, CO2 concentration in the substamatic chamber, internal carbon / atmospheric carbon ratio, water efficiency and absolute coffee growth rate were influenced by the different compaction degrees and soil moisture content. The transpiration rate and the root weight ratio were influenced only by the humidity, as opposed to the stomatal conductance and the foliar temperature, which were by degrees of compaction. The ratio of root system per soil layer was influenced by compaction degrees and soil depth. The limitation of root growth and lack of water are the main causes of the decrease in physiological responses. Subsurface compaction and water deficit together potentiate the effect negatively on the physiological responses of freshly seeded coffee plants.

GPR imaging of traffic compaction effects on soil structures

Spatial and depth variability of soil characteristics greatly influence its optimum utilization and management. Concealing nature of soil subsurface horizons has made the traditional soil investigations which rely on point information less reliable. In this study, an alternative use of ground penetrating radar (GPR)—a near-surface geophysical survey method—was tested to address the shortcomings. The focus of the study was on assessment of characteristics variability of soil layers at a test site and evaluation of effects of compaction caused by machinery traffics on soil. GPR methods utilize electromagnetic energy in the frequency range of 10 MHz and 3.0 GHz. Fourteen profiles GPR data were acquired at the test site-a farmland in Krakow, Poland. Compaction on parts of the soil was induced using tractor movements (simulating traffic effects) at different passes. Data were processed using basic filtering algorithms and attributes computations executed in Reflexw software. Attempt made in the study was on use of GPR geophysical technique for soil assessment. The method allows delineation of the soil horizons which depicts characteristic depth changes and spatial variability within the horizons. Moreover, traffic effects that caused compaction on parts of the soil horizons were discernable from the GPR profile sections. Thus, similar densification like hardpan that may develop in natural setting can be investigated using the method. The results have shown the suitability of the method for quick, noninvasive and continuous soil investigation that may also allow assessment of temporal soil changes via repeated measurement.

Nutrient concentrations in trifoliate orange as affected by lime and gypsum

Use of trifoliate orange [Poncirus trifoliata (L.) Raf.] as a rootstock has intensified in recent years in Brazil. Objectives of this study were to evaluate the effects of lime and agricultural gypsum on concentration of nutrients in trifoliate orange. Seedlings of trifoliate orange were grown in PVC pipe columns, presenting 15 cm in diameter and 35 cm in length. The columns were sectioned in two rings: the upper ring, 15 cm high, and the lower ring, 20 cm high. The factorial scheme (2×4)+1 was used, being two liming treatments and four agricultural gypsum doses (carried out only in the soil of the upper ring), and an additional treatment (with liming carried out in the soil of both upper and lower ring). Liming increased Mg and S concentrations in roots of the superficial soil layer (0-15 cm). Ca concentration was higher in roots of both superficial (0-15 cm) and subsuperficial (15-35 cm) layers. Gypsum without liming resulted in higher N, K, and Mn concentrations and lower Mg concentration in roots of the soil subsurface layer. Ca and S concentrations in root of the soil superficial layer were higher with gypsum. In plant shoot, the concentrations of K, Ca, S and Cu were higher with liming, and concentrations of Ca and P were higher and lower, respectively, with gypsum application.

On evapotranspiration and eddy covariance measurements corrections

Eddy Covariance (EC) technique is one of the most used technique monitoring Green House Gases (GHG) fluxes such as H2O, CO2, CH4. Water vapor movement and corresponding air density fluctuations were corrected by Webb et al. (1980) but not water vapor formation. Classic EC technique supposes mean air vertical speed nullity when it cannot be the case because of water evaporation. Water is falling as a liquid, evaporating directly from soil surface, from shallow soil subsurface or either through vegetation transpiration and becomes a gas which corresponds to a notable volume expansion. Water vapor is mounting through atmosphere, compensating in a cloud and falling as a rain (liquid) again. Evaporation and corresponding volume expansion make mean vertical air speed positive (upgoing) and influence more or less a flux balance following concerned gas or energy. A simple accessing and corresponding correction for the half hourly summation is given and applied to a 11-month real set of data. These corrections allow to explain, in part, most observed eddy covariance discrepancies.

Impacts of Phosphate Amendments at a Contaminated Site

Soil amendments can be used to cost-effectively reduce the bioavailability and mobility of toxic metals in contaminated soils. Phosphate amendments effectively can be transformed to soil from the non-residual (sum of exchangeable, carbonate, Fe/Mn, and organic) to the residual fraction. Metal immobilization can be attributed to the metal-induced formation of chloropyromorphite which can be identified in the surface soil, subsurface soil, and plant rhizosphere soil. Phosphate treatments can significantly reduce metal translocation from the roots to the shoots in the plants/crops possibly via the formation of chloropyromorphite on the cell walls of roots. Application of combined H3PO4 with phosphate rock can be provided an effective alternative to the current phosphate remediation technologies for contaminated soils.