Soil and Plant Nutrient Analysis with a Portable XRF Probe Using a Single Calibration

A portable X-ray fluorescence probe (pXRF) is a tool that is used to measure many elements quickly and efficiently in various samples, without any pretreatment. However, each type of sample generally requires different calibrations to be accurate. To overcome this, our work evaluated the efficacy of determining several elements in forage plant samples using the ‘Soil Nutrient and Metal’ calibration in a commercially available pXRF probe, envisioning that a single calibration can be used to measure samples of different matrixes. For this, the net intensity of the pXRF probe was determined in place of the concentration values that are obtained directly from measurements. Elemental concentrations (P, K, Ca, Mg, S, Cu, Fe, Zn, and Mn) from forage plant samples, collected across Oklahoma, US, were assessed in a representative number of ‘modeling’ and ‘validation’ (independent dataset) samples. Linear regression (LR) associated with the d-index, polynomial regression (PR), and power regression (PwR) were tested for predictions, producing many statistical parameters associated with the models that were used for comparison goals. The pXRF elemental data provided highly reliable predictions of K, S, Zn, and Mn regardless of the regression model. Although all models can be reliable in prediction of Ca and Fe concentrations, the PwR provided better root mean square error (RMSE) values. The predictions of Mg concentrations were less reliable, although highly significant; however, the P and Cu predictions were not acceptable. Our work successfully showed that, once established, a single calibration curve that covers a wide range of concentrations of several elements in soils and plant tissues enables both soil and plant samples to be analyzed. This suggests that manufacturers can develop a new calibration model for a commercially available pXRF probe that covers a wide variety of heterogeneous samples.

Effect of Forage Plant Mixture and Biostimulants Application on the Yield, Changes of Botanical Composition, and Microbiological Soil Activity

Recently, an increasing interest in such fertilizers and fertilization methods which not only directly supply nutrients to plants, but also stimulate soil bioactivity is noted. Their effect on both soil microbiota and forage plants has not been fully recognized. The aim of the study was to investigate the combined effect of forage plant mixture type and mineral fertilizers (NPK) with biostimulants based on a marine algae extracts on the botanical composition, yield, the structure of selected taxonomic and trophic groups of soil microorganisms, and the soil enzymatic activity. During the years 2018–2019 a field experiment established in split-plot design with two different forage plant mixtures, as a first factor, and different fertilization basing on mineral fertilizers amended with biostimulants, as a second factor was conducted. Two types of forage mixtures of sown species were used: grass mixture (GM) and legume-grass mixture (LGM). Every year the following biostimulants were applied: N-14, PinKstart, Physiostart, Physioactive and they were compared with standard NPK fertilisation and no fertilisation as a control. The reaction of forage plant mixtures on applied fertilisation was different. The intensive development of grass species, mainly Lolium perenne, at the expense of Trifolium repens share in LGM was observed. In GM sward dominated Dactylis glomerata. A beneficial effects of biostimulants’ application on the biomass yields of both grass mixtures was observed. The systematic soil acidification and a decrease of soil enzymatic activity in result of applied fertilization, except NPK + Physioactive treatment (calcium fertilizer containing 76% calcium carbonate), was noted. Soil reaction to applied fertilisation was dependent on the botanical composition of the sward. The counts of microorganisms in the soil under LGM were almost two times higher than in the soil under GM. The most effective, in reducing the negative effect of nitrogen mineral fertilization on the pH of soil, was fertilization with NPK + Physioactiv.

Evaluation of the influence of heavy metals on the degree of damage Cameraria ohridella Deschka & Dimič, 1986 leaf surface of Aesculus hippocastanum Linnaeus, 1753

The work presents the results of research on effect of heavy metals (Zn, Cu, Pb, Cd) on degree of horse chestnut (Aesculus hippocastanum Linnaeus, 1753) leaf surface damage by chestnut miner (Cameraria ohridella Deschka & Dimič, 1986) caterpillars. Analysis of leaf blade damage of the forage plant species by C. ohridella was conducted for four years (2017–2021). The research covered all the main park urban ecosystems in Dnipro city where horse chestnut trees were planted. Monitoring was carried out during the three summer months, which corresponds to the main feeding period of the three most active C. ohridella generations (I, II, and III). About 96 samples were used and prepared for atomic absorption analysis to study the content of heavy metals in A. hippocastanum leaf blades. On the territory of the park ecosystems in Dnipro city, eight groups of model horse chestnut trees of 20–30 years of age were identified which have similar morphological and taxonomic features but different degrees of leaf damage by C. ohridella miner. Since the plantations of horse chestnut are mainly located in an urban environment, we conducted research to test the hypothesis about the influence of heavy metals on C. ohridella vital activity. Presumably, the content of heavy metals also affects the degree of leaf blade damage. In this regard, we conducted research on the content of heavy metals in A. hippocastanum leaf tissues. It was found that accumulation in the horse chestnut leaf tissues of four basic heavy metals (Zn, Cu, Pb, Cd) contained in all urban environments depends on the orographic features of the area where A. hippocastanum trees grow. It also was found that the higher in relief were located the horse chestnut plantings, the greater the percentage of their invasion by the miner, and this trend was observed during the three summer months. For example, in the Manuylivsky Park where horse chestnut trees are located at 56 m above sea level, the average leaf invasion by the miner in August is 14%; in the same month in Oles Honchar Dnipro National University Botanical Garden (149 m), the level of invasion was 78%. Research on the effects of heavy metals on C. ohridella populations also showed significant differences by the types of urban ecosystems. It was found that the higher content of heavy metals in the leaf tissues in a forage plant, the greater percentage of their surface damage by mines.