Nitrogen leaching in croplands is a worldwide problem with implications both on human health and on the environment. Efforts should be taken to increase nutrient use efficiency and minimize N losses from terrestrial to water ecosystems. Soil-applied biochar has been reported to increase soil fertility and decrease nutrient leaching in tropical soils and under laboratory conditions. Our objective was to evaluate the effect of biochar addition on short-term N leaching from A soil horizon in a mature apple orchard growing on subalkaline soils located in the Po Valley (Italy). In spring 2009, 10 Mg of biochar per hectare was incorporated into the surface 20-cm soil layer by soil plowing. Cumulative nitrate (NO) and ammonium (NH) leaching was measured in treated and control plots 4 mo after the addition of biochar and the following year by using ion-exchange resin lysimeters installed below the plowed soil layer. Cumulative NO leaching was not affected by biochar after 4 mo, whereas in the following year it was significantly ( < 0.05) reduced by 75% over the control (from 5.5 to 1.4 kg ha). Conversely, NH leaching was very low and unaffected by soil biochar treatment. The present study shows that soil biochar addition can significantly decrease short-term nitrate leaching from the surface layer of a subalkaline soil under temperate climatic conditions.

To best use biochar as a sustainable soil management and carbon (C) sequestration technique, we must understand the effect of environmental exposure on its physical and chemical properties because they likely vary with time. These properties play an important role in biochar's environmental behavior and delivery of ecosystem services. We measured biochar before amendment and four years after amendment to a commercial nectarine orchard at rates of 5, 15 and 30tha(-1). We combined two pycnometry techniques to measure skeletal (ρs) and envelope (ρe) density and to estimate the total pore volume of biochar particles. We also examined imbibition, which can provide information about soil hydraulic conductivity. Finally, we investigated the chemical properties, surface, inner layers atomic composition and C1s bonding state of biochar fragments through X-ray photoelectron spectroscopy (XPS). Ageing increased biochar skeletal density and reduced the water imbibition rate within fragments as a consequence of partial pore clogging. However, porosity and the volume of water stored in particles remained unchanged. Exposure reduced biochar pH, EC, and total C, but enhanced total N, nitrate-N, and ammonium-N. X-ray photoelectron spectroscopy analyses showed an increase of O, Si, N, Na, Al, Ca, Mn, and Fe surface (0-5nm) atomic composition (at%) and a reduction of C and K in aged particles, confirming the interactions of biochar with soil inorganic and organic phases. Oxidation of aged biochar fragments occurred mainly in the particle surface, and progressively decreased down to 75nm. Biochar surface chemistry changes included the development of carbonyl and carboxylate functional groups, again mainly on the particle surface. However, changes were noticeable down to 75nm, while no significant changes were measured in the deepest layer, up to 110nm. Results show unequivocal shifts in biochar physical and chemical properties/characteristics over short (~years) timescales.

Background and Aims:  Copper accumulation in soil may promote phytotoxicity in grapevines. Nutritional implications of potted vines to increasing concentrations of copper (Cu) in either clay loam soil or clay loam soil mixed with 85% sand were tested on Vitis vinifera (L.) cv Sangiovese and crop toxicity threshold and symptoms determined. Methods and Results:  Soils were mixed at planting with Cu at the rates (mg Cu/kg) of 0 (control, native soil Cu only), 50, 100, 200, 400, 600, 800 and 1000, and non‐bearing vines were grown in these for two seasons. Reduction of root growth was observed after addition of ≥400 mg Cu/kg to both soils; reduction of shoot growth, leaf number and chlorosis of leaf edges were detected only in sand‐enriched soil. Root Cu concentration increased in response to soil Cu addition. Unlike that of leaf Cu and N, the amount of P and Fe (in both soils) and Mg and Ca (in sand‐enriched soil only) were reduced by soil Cu. Conclusion:  Vines grown in sand‐enriched soil tolerated lower concentrations of Cu than in clay loam soil, probably because of the lower nutritional status and the higher root Cu concentration. Significance of the Study:  Results provide information on the concentration of soil Cu that grapevine can tolerate and on the nutrients involved in the response to toxic levels of soil Cu in clay loam and sandy clay loam soils.

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Summary Biochar addition to soil has been suggested as a promising strategy to increase soil carbon storage with important side‐effects on soil fertility and crop productivity. Understanding the effect of biochar on soil respiration partitioning into rhizosphere‐derived (Fr) and soil organic carbon‐derived (Fsoc) components and on plant root dynamics and microbial activity is a crucial issue in the prediction of the impact of biochar on soil organic carbon and nutrient cycles. Within this framework, an experiment was carried out in an apple (Malus domestica Bork) orchard located in the experimental farm of the Bologna University (Italy). In spring 2009, 10 t of biochar per hectare were incorporated into the surface 20‐cm soil layer by soil ploughing. The trenching method was used in order to partition total soil respiration (Fs) into Fr and Fsoc components in both biochar‐treated and control soil. Soil respiration measurements were performed from June 2009 to March 2011. To study root dynamics, polycarbonate boxes were built and buried into the soil. Soil profile pictures were collected fortnightly with a CCD sensor scanner inserted in the boxes and analysed with the WinRHIZO Tron MF software. Biochar addition increased Fsoc and reduced Fr, even if the root length intensity (La) increased in biochar‐treated soils relative to that in the control. A decrease in root metabolic activity was postulated to explain these contrasting results.

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Kiwifruit production has gained great importance in Italy, becoming a strategic crop in several areas. In recent years, the Italian kiwifruit industry has been threatened by the emergence of a new, idiopathic syndrome causing a severe and rapid decline, leading to vine collapse within two years from symptom development. The main symptoms associated to this syndrome are the disappearance of feeding roots, blocking of both stele and xylem vessels, root cortex breakdown, leaf necrosis, phylloptosis, twig wilting and plant death. Kiwifruit decline affects both Actinidia chinensis var. chinensis and A. chinensis var. deliciosa. Due to the similarity with other fruit trees idiopathic diseases, such as the rapid apple decline, we propose to name this disorder as kiwifruit vine decline syndrome (KVDS). The causes of KVDS are still unknown. However, KVDS is prevalent in soils affected by waterlogging or poor aeration, suggesting a physiological origin of this disorder. In addition, our experiments suggested a role of the rhizosphere microbial community, since healthy and KVDS-affected plants show distinct bacterial and fungal communities. Phytophthora spp. and Phytopythium spp. were more frequent in symptomatic plants (58.6%) than in asymptomatic ones (19%). Moreover, Desarmillaria tabescens were found only on symptomatic plants. Inoculation of potted kiwifruit vines with those pathogens resulted in KVDS symptom development. Finally, induced waterlogging conditions increased the incidence of pathogen isolation, but not the symptom development.

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