Search

The replacement of synthetic chemical herbicides and traditional plastic sheets is a major challenge of modern horticulture in view of a sustainable weed management. In the first step of this research, we tested the weed control efficacy of two biodegradable polymers, chitosan and galactomannan, applied to the soil surface as spray mulching, with or without the addition of charcoal as a light masking agent, and five essential oils with recognized herbicide properties. The results showed the ability of chitosan in reducing the number and the biomass of annual plants, regardless of the addition of charcoal and essential oils. In the second step, we tested the efficacy of one or three days of false seeding to increase the effectiveness of chitosan against seed germination. The results showed, on average, a reduction of 79% of annual weed presence after three days of false seeding. In both steps, the microbial biomass and three indicators of microbial activity (i.e., basal respiration, FDA hydrolysis activity, and D-glucosamine-induced respiration) were measured in the soil under the experiments in order to investigate possible alterations of soil biological activity induced by the treatments. The results provided no evidence of negative impact of the treatments on soil microbial biomass and activity. [ABSTRACT FROM AUTHOR]

Intensive greenhouse vegetable production is often associated with a decline of crop productivity due to the increase of soil salinity and/or a reduction of biological fertility. The aim of the current work was to assess the effects of three organic fertilizers on morpho-physiological and agronomic traits of greenhouse lettuce as well as soil enzyme activity under poor soil quality conditions. The tested organic fertilizers (poultry manure, vinasse-based fertilizer, and insect's frass fertilizer) were applied pre-planting at the same equivalent nitrogen (N) rate (90 kg N ha−1). Laboratory incubation assay results showed that vinasse-based fertilizer was the most suitable fertilizer in supplying the mineral N in the short term. All fertilizers increased shoot fresh and dry weight compared to unfertilized control with a more pronounced effect (+75%) with vinasse-based fertilizer and insect's frass. Insect frass reduced by 27% the leaf nitrate concentration in comparison with the other treatments. The toxic heavy metal Pb was 46% lower in all organically fertilized lettuce leaves. Soil enzymatic activities of acid phosphatase, alkaline phosphatase, arylsulfatase (ArS), N-acetyl-β-D-glucosaminidase (NAGase), dehydrogenase, and total hydrolase (THA) were enhanced by poultry manure and insect's frass in comparison with unfertilized control while vinasse-based fertilizer increased ArS, NAGase, and THA. Taken together, our data demonstrate that the application of organic fertilizers especially vinasse-based fertilizer and insect's frass during intensive crop production is a suitable approach for mitigating the negative impact of soil salinity, enhancing soil biological fertility, and improving agronomic performance of greenhouse lettuce. [ABSTRACT FROM AUTHOR]

Chemometric analysis applied to diffuse reflectance spectroscopy is increasingly proposed as an effective and accurate methodology to predict soil physical, chemical and biological properties. Its effectiveness, however, largely varies in relation to the calibration techniques and the specific soil properties. In addition, the calibration of UV-Vis-NIR spectra usually requires large datasets, and the identification of techniques suitable to deal with small sample sizes and high dimensionality problems is a primary challenge. In order to investigate the predictability of many soil chemical and biological properties from a small dataset and to identify the most suitable techniques to deal with this type of problems, we analysed 20 top soil samples of three different forests (Fagus sylvatica, Quercus cerris and Quercus ilex) in southern Apennines (Italy). Diffuse reflectance spectra were recorded in the UV-Vis-NIR range (200-2500 nm) and 22 chemical and biological properties were analysed. Three different calibration techniques were tested, namely the Partial Least Square Regression (PLSR), the combinations wavelet transformation/Elastic net and wavelet transformation/Supervised Principal Component (SPC) regression/ Least Absolute Shrinkage and Selection Operator (LASSO), a kind of preconditioned LASSO. Calibration techniques were applied to both raw spectra and spectra subjected to wavelet shrinkage filtering, in order to evaluate the influence on predictions of spectra denoising. Overall, SPC/LASSO outperformed the other techniques with both raw and denoised spectra. Elastic net produced heterogeneous results, but outperformed SPC/LASSO for total organic carbon, whereas PLSR produced the worst results. Spectra denoising improved the prediction accuracy of many parameters, but worsen the predictions in some cases. Our approach highlighted that: (i) SPC/LASSO (and Elastic net in the case of total organic carbon) is especially suitable to calibrate spectra in the case of small, high dimensional datasets; and (ii) spectra denoising could be an effective technique to improve calibration results. [ABSTRACT FROM AUTHOR]

A forest soil located in the 'Parco Nazionale del Cilento e del Vallo di Diano', Salerno, Italy, has been partly converted to a crop field by deforestation and a deep tillage (mouldboard plowing), characterized by an inversion of soil profile at a depth of 1 m, followed by plowing. In this study, we compare soil quality in a crop field and in the adjacent unchanged forest. Soil samples were collected from the two sites few months after the use change and characterized for main chemical (pH, electrical conductivity, organic C, total N, available P, cation exchange capacity) and microbiological (enzyme activities related to cycles of major nutrients, catabolic response profiles, microbial and fungal biomass) properties. We found a depletion of 50 % in soil organic C content in the crop field in comparison with forest, which indicates that the quality of the top layer of the soil decreased, with consequent deep alteration of the C cycle. The drop of organic matter content determined serious effects on soil microbial activity. Microbial and fungal biomass, as well as all enzyme activities, were decreased. The soil catabolic response profiles showed a significant reduction in functional diversity in the cultivated compared to the forest soil. Among the investigated properties, dehydrogenase and β-galactosidase activities, ergosterol content and catabolic evenness showed the highest sensitivity to the soil use change, suggesting that they could be assumed as indicators of the stress induced by this use change. [ABSTRACT FROM AUTHOR]

The effect of soil moisture on bacterial growth was investigated, and the effects of rewetting were compared with glucose addition because both treatments increase substrate availability. Bacterial growth was estimated as thymidine and leucine incorporation, and was compared with respiration. Low growth rates were found in air-dried soil, increasing rapidly to high stable values in moist soils. Respiration and bacterial growth at different soil moisture contents were correlated. Rewetting air-dried soil resulted in a linear increase in bacterial growth with time, reaching the levels in moist soil (10 times higher) after about 7 h. Respiration rates increased within 1 h to a level >10 times higher than that in moist soil. After the initial flush, there was a gradual decrease in respiration rate, while bacterial growth increased to levels twice that of moist soil 24 h after rewetting, and decreased to levels similar to those in moist soil after 2 days. Adding glucose resulted in no positive effect on bacterial growth during the first 9 h, despite resulting in more than five times higher respiration. This indicated that the initial increase in bacterial growth after rewetting was not due to increased substrate availability. [ABSTRACT FROM AUTHOR]

In the National park of Cilento, Vallo di Diano and Alburni (South Italy), a portion of a chestnut forest was converted in 2012 into an agricultural system in order to crop a local variety of bean. We investigated the effect over time of the conversion on the functional diversity of the soil microbial community by two different approaches: the catabolic response profile, based on the short time CO2 evolution induced by 25 simple organic substrates and the Biolog community level physiological profile (CLPP), based on the growth of microorganisms on 31 different substrates. The soils were sampled at 13, 17, 29, 41 and 49 months after the soil use change. The results showed that the soil use change did not produce evident modifications of the substrate utilization patterns, but rather a general decrease in the activity in the agricultural soils, as a consequence of the reduction in organic matter content. The results also showed seasonal effects on the substrate utilization profiles and on the calculated functional diversity indexes. The two approaches appeared to be complementary: Degens catabolic response profile was more able to discriminate between the two systems, whereas the Biolog was more able to highlight the variability among samplings. [ABSTRACT FROM AUTHOR]