Fábio Joel Kochem Mallmann

Peach tree (Prunus persica L. Batsch) is a fruit species of great economic importance worldwide. Thousands of chemical leaf analyses are performed on a yearly basis to support decision-making about fertilizer application. However, traditional methods to determine nutrient content in plant tissue require a mix of strong acids, besides being time-consuming and generating polluting waste. Visible (Vis) and near-infrared (NIR) spectroscopy combined with multivariate techniques emerges as a potential solution to overcome limitations of traditional chemical analyses. The aim of the present study is to combine Vis-NIR spectral data and multivariate techniques to test strategies for the development of models to estimate nutrient content in peach leaves. The study estimated N, P, K, Ca, Mg, S, B, Cu, Fe, Mn, and Zn content in the leaves of peach trees grown in two locations, namely: Pelotas and Pinto Bandeira, in Southern Brazil. Therefore, local and regional scale prediction models were developed by combining preprocessed Vis-NIR spectral data to both Savitzky–Golay first-derivative (SGD1d) and partial least squares regression (PLSR) multivariate technique. Most of the proposed prediction models showed average accuracy (R² ≥ 0.50 and <0.75, RPIQ ≥ 1.9 and <3.0). The local-1 ‘PB’ model showed higher nutrient prediction accuracy than the regional ‘PB + Pelotas’ model and the local-2 ‘Pelotas’ model. Estimates on nutrient content in peach tree leaves subjected to local, local-1 ‘PB’ and local-2 ‘Pelotas’ models fed with data collected in the same site showed better performance than calculations based on data from other sites and/or regions. Finally, the current study allowed making updates in the refinement of more sustainable techniques to set nutrient content.

Kiwi orchards can be established on acidic soils with low nutrient availability, requiring amendments and fertilizers to meet the plant’s nutritional requirements. However, nutritional information requirements of the crop are scarce, which can support fertilizer recommendations. This study aimed to establish critical levels (CL), soil fertility classes (FC), and leaf sufficiency ranges (SR) of nutrients for kiwi cultivation in Southern Brazil. Diagnostic standards from commercial orchards were established using a database (fruit yield, nutrient levels in soil, and leaves). To establish CL, FC, and SR, the fruit yield was related to nutrient levels, and models were established using the boundary line (BL) method and Bayesian quantile regression models. The FC for soil available P and K levels were 30–37 and 127–135 mg·dm-3, respectively, while exchangeable Ca and Mg were 10–14 cmolc·dm-3 and 3.5–5.0 cmolc·dm-3, and V was 82–88%. In leaf tissue, the SR for N, P, K, Ca, Mg, and S were 27–31, 1.6–2.2, 18–22, 22–25, 4.2–7.5, and 2.1–4.2 g·kg-1, respectively. For micronutrients, the SR were 57–65 mg·kg-1 for Cu, 247–255 mg·kg-1 for Fe, 95–102 mg·kg-1 for Mn, 20–25 mg·kg-1 for Zn, and 10–13 mg·kg-1 for B. The diagnostic standards for soil fertility and plant nutritional status obtained in this study can be used by kiwi growers to increase fruit yield.

Bases are chemical species that donate electrons, accept protons, or release hydroxyls (OH–) in aqueous solution. In Soil Science, “base saturation”, “exchangeable bases” or “basic cations” has been widely used to distinguish Ca2+, Mg2+, Na+, and K+ from H+ and Al3+ cations. This terminology is confusing since none of these cations are truly a base in chemistry sense. However, in the absence of the proposition of a correct term, the term “base saturation” remains in use nowadays, causing confusion [...] ABSTRACT Bases are chemical species that donate electrons, accept protons, or release hydroxyls (OH–) in aqueous solution. In Soil Science, “base saturation”, “exchangeable bases” or “basic cations” has been widely used to distinguish Ca2+, Mg2+, Na+, and K+ from H+ and Al3+ cations. This terminology is confusing since none of these cations are truly a base in chemistry sense. However, in the absence of the proposition of a correct term, the term “base saturation” remains in use nowadays, causing confusion

The objective of this study was to evaluate the short-term dynamics of chemical species of sulfate and the main basic cations in the soil solution affected by the application of different sulfur (S) rates using agricultural gypsum. The experiment was carried out in an Ultisol with 14% clay, managed under no-tillage for 14-yr in Southern Brazil. Four rates of S (0, 5, 10 and 20 kg of S ha⁻¹) were evaluated using agricultural gypsum (CaSO₄) as S-source. The soil solution was collected using porous capsule lysimeters before and at 9, 17, 37, 60, 76 and 109 d after the gypsum application, at depths of 20 and 60 cm. Surface application of gypsum rapidly increases the sulfate concentration in the soil solution at 20 cm depth. However, in less than 30 d, the effect of the S rates on the soil solution at 20 cm was minimal, with an increase in sulfate concentration in the soil solution at 60 cm depth after 17 d. Sulphated fertilization via agricultural gypsum at rates greater than 10 kg ha⁻¹ in sandy soil with low cation exchange capacity increased the mobility of Ca and Mg in the soil profile.

In Southern Brazil, agricultural soils are often treated over long periods with annual pig slurry (PS) applications, and their influence on soil nutrient dynamics should be monitored. This study aimed to evaluate the P forms accumulated in the soil and some biological and biochemical parameters of the P cycle after 19 successive PS applications over eight years, in a no-tillage (NT) system. Pig slurry was applied at rates of 0, 20, 40, and 80 m³ ha^-1 per crop. Several P forms (available P, microbial P, phosphatase enzyme, total organic and inorganic P) in the 0.00-0.05 and 0.05-0.10 m soil layers were analyzed. Increases up to 5,523 % in available P, 308 % in microbial P, 104 % in phosphatase enzyme activity, 91 % in organic P, 251 % in inorganic P, and 19 % in Total-P were observed in the 0.00-0.05 m soil layer in response to the highest PS rate compared to the treatment with no PS. Results also indicated that P added via PS was preferentially accumulated in the inorganic fractions (83-98 %). The increase in organic P was limited by the increase in soil organic carbon. The increase in soil microbial biomass-P was more influenced by available P, while the increase in phosphatase enzyme activity was more related to the increase in organic P and C. Therefore, PS applied to the soil affected the chemical, biological, and biochemical components of the soil P cycle. Results indicate that even half of the PS rate normally used by farmers (20 m³ ha^-1) poses a high risk of pollution of water bodies by runoff from these soils.

Core Ideas: Eleven years of Zn and Cu movement in an Oxisol amended with pig slurry (PS) was modeled. Root growth and water uptake effects were successfully added in HYDRUS simulations. Concentration profiles of Zn were described better than those of Cu. DOC‐facilitated Cu transport needs to be considered when modeling Cu transport in soils. Zn concentrations will not be a problem during the next 50 yr in PS‐amended soils. Increases in Zn and Cu concentrations in soils amended with pig slurry (PS) can be described using numerical models. Our main objective was to validate that the HYDRUS‐1D model is able to numerically describe profile concentrations and long‐term vertical transport of Zn and Cu in a clay soil (Oxisol) cultivated under annual cropping in a no‐till system and contaminated by successive doses of PS amendments. We first used a modeling approach that had previously been validated for an Alfisol. Then, we additionally also evaluated the effects of root growth and root water uptake on the transport of trace metals (TMs). Finally, we carried out 50‐yr‐long prospective simulations for different doses of PS amendments. Consideration of root growth and root water uptake processes in HYDRUS‐1D simulations improved the description of measured field Zn concentrations. Although the correspondence between simulated and measured Cu concentrations was not as good as for Zn, we performed prospective simulations for both elements. Future scenarios that considered large PS doses showed large increases in concentrations of both TMs in the soil surface layer. The feasibility of using PS amendments on agricultural Oxisols will be limited by Cu because the soil Cu threshold concentration is exceeded in approximately 29 yr. Moreover, the total loads of both TMs allowed on agricultural soils are reached very fast when large rates are used, especially for Cu (19 yr), indicating that the long‐term disposal of PS on agricultural soils should be done at low doses. These conclusions are probably conservative because our model did not consider potential leaching of TMs from the surface soil into deeper soil layers by dissolved organic C facilitated transport.