Quanti-qualitative response of Swiss Chard (Beta vulgaris L. var. cycla) to soil amendment with biochar-compost mixtures

In recent years, soil addition with organic amendments, such as biochar and compost, has gained attention as an effective agronomic practice to sustain soil fertility, enhance plant growth and crop yield. Well known are the positive effects of compost on yield of a wide crop varieties, while both positive and negative responses are reported for biochar Therefore, the aim of the study was to verify the effect of biochar mixed with three types of compost on quanti-qualitative response of Swiss chard (Beta vulgaris L. cycla), a leafy green vegetable rich in dietary antioxidants, largely consumed worldwide. A factorial experiment in pots with two factors, including biochar (without biochar and with biochar from vine pruning residues) and compost (without compost, with compost from olive pomace, with vermicompost from cattle manure, and with compost from cattle anaerobic digestate), was setup. Two growth cycles were considered, and a set of quantitative (height of plants, number, area and fresh weight of leaves) and qualitative parameters (carotenoids, chlorophyll, total N, and NO3−content of leaves) were analyzed. Biochar decreased plant growth and NO3− leaf content; on the contrary, it increased total N leaf content, while compost improved all the considered parameters. The interactive effect of biochar and compost was evident only on total N and NO3− leaf content. In our experimental conditions, the compost showed to be the best option to improve Swiss chard growth and increase the content of phytopigments, while the biochar-compost mixtures did not produce the expected effect

Effect of biochar and inorganic or organic fertilizer co-application on soil properties, plant growth and nutrient content in Swiss Chard

From the perspective of sustainable agri-food production, farmers need to make the best use of natural resources. Biochar can be a solution to adopt a more sustainable way of farming. Despite its environmental and agronomic advantages, biochar has a low plant nutrient value. This study evaluated the effect of biochar and the co-application of an inorganic or organic fertilizer on the soil properties, growth and nutrient content of Swiss chard (Beta vulgaris L. var. cycla, Caryophyllales order, Chenopodiaceae family). The experiment consisted of two factors: biochar type (from vineyard prunings and wood chips) and fertilizing source (ammonium nitrate and vermicompost). Biochars were applied at a 2% rate (w/w) and fertilizers at a dose providing 280 kg N ha(-1). The soil properties (pH, EC, extractable anions, cations, total N, Corg and C/N ratio) were measured before the plants were transplanted and at the end of the growing cycle, along with the growth parameters (leaf number, length and fresh weight) of each leaf cut, the productive parameters (total number of leaves and yield per plant) at the end of the growing cycle and the leaf content of anions (NO3-, P2O43-, SO42-), cations (NH4+, Na+, K+, Ca2+, Mg2+) and total N. The co-application of biochar and a fertilizing source had a positive effect on soil properties and leaf nutrient content. Vermicompost increased plant growth by 22% and plant yield by 116%, in contrast to biochar, and increased limited leaf NO3- accumulation by about 81% in comparison to ammonium nitrate. The co-application of biochar and vermicompost is the better option to increase Swiss chard yield while preserving the nutritional and health qualities of the product

Evaluation of Vegetative Development of Quinoa under Water Stress by Applying Different Organic Amendments

Prolonged drought periods, increasingly occurring worldwide due to global climate change, could affect the growth and productivity of both traditional and climate-resilient crops, including quinoa. Specifically, the vegetative growing cycle of this species is highly sensitive to drought conditions. In this context, using organic amendments could help plants cope with drought due to their ability to enhance soil water status. So, the current study aimed to investigate the effect of different organic amendments, i.e., two biochars (from woodchips and vineyard prunings) and a vermicompost (from cattle manure), applied to the soil alone and mixed at 2% rate (w/w), on the vegetative development of quinoa (cv. Titicaca), during which a period of water stress was imposed from the twelve-leaf stage to the bud stage. A set of growth-related parameters were measured both during and at the end of the experiment, along with a set of water-related parameters, at the end of the water-stress period and after soil re-watering. The results showed that woodchip biochar, both alone and mixed with vermicompost, significantly affected plant growth during the water-stress period, also allowing a quicker recovery once drought conditions ended. Indeed, the leaf number and area, SPAD index, leaf and stem fresh weight, and dry matter content in plants treated with woodchip biochar, alone and mixed with vermicompost, were higher than vineyard pruning biochar, alone and mixed with vermicompost and similar to the well-watered control plants. Similar results were observed considering the yield contributing traits detected at the end of the experiment, including the main panicle length, number of sub-panicle, as well as fresh weight and dry matter content of both panicle and sub-panicles. Additionally, the water-related parameters, especially the low turgid weight to dry weight ratio of woodchip biochar treated plants, showed evidence of better growth than vineyard pruning biochar. At the end of the experiment, the WUE of plants treated with woodchip biochar and vermicompost, both alone and mixed, was higher than vineyard pruning biochar alone and mixed with vermicompost. Among the tested organic amendments, woodchip biochar alone and mixed with vermicompost positively affected the vegetative growth response of quinoa under water-stress conditions

Effect of biochar amendment on nitrate retention in a silty clay loam soil

Biochar incorporation into agricultural soils has been proposed as a strategy to decrease nutrient leaching. The present study was designed to assess the effect of biochar on nitrate retention in a silty clay loam soil. Biochar obtained from the pyrogasification of fir wood chips was applied to soil and tested in a range of laboratory sorption experiments. Four soil treatments were considered: soil only (control), soil with 2, 4 and 8% of biochar by mass. The Freundlich sorption isotherm model was used to fit the adsorbed amount of nitrate in the soil-biochar mixtures. The model performed very well in interpreting the experimental data according to a general linear regression (ANCOVA) statistical approach. Nitrate retention in the soil-biochar mixtures was always higher than control, regardless the NO3- concentration in the range of 0-400 mg l-1. Different sorption capacities and intensities were detected depending on the biochar application rate. The highest adsorption capacity was observed in the soils added with 2 and 4% of biochar, respectively. From the results obtained is possible to infer that nitrate retention is higher at lower biochar addition rate to soil (2 and 4%) and at lower nitrate concentration in the soil water solution. These preliminary laboratory results suggest that biochar addition to a typical Mediterranean agricultural soil could be an effective management option to mitigate nitrate leaching

Salt leaching due to rain in Mediterranean climate: is it enough?

The increasing limitation of available water resources for agriculture raises the issue of an appropriate use of low quality water (particularly brackish or saline water) for agricultural productivity without jeopardizing the quality of soil and its productive capacity. Referring to typical Mediterranean climate conditions and assuming a systematic irrigation use of brackish groundwater, this paper analyzes the capability of yearly rainfall, particularly in fall-winter period, to leach the salts accumulated in the soil during the previous spring-summer irrigation season. The leaching capability of water supplies exceeding the soil water holding capacity has undergone direct evaluation through a particular experimental arrangement: under a rain shelter, soil columns (inside special cylindrical containers), previously salinized and bare at the surface, were treated with repeated irrigations. Fresh water was used for this purpose, in order to simulate rainwater. The amounts and proportions of salt removed from the soil as well as the relative quantity of salt left in the soil were monitored. An appropriate statistical data analysis led to the interpretation of the observed process by developing a leaching curve able to predict the fraction of salts remaining along the soil profile according to the height of leaching water added to the soil, expressed as a fraction of the depth of the soil layer considered. According to the experimentally determined "leaching curve" (related to a silt-loam textured soil, basically unstructured and compacted as a result of a prolonged salinization), the following rule of thumb can be taken: the application of a defined height of leaching fresh water reduces by 70% (i.e. reduces to 30%) the salt content of a soil layer of equal depth. The elaboration of this conveniently parameterized "leaching curve" prompted an attempt to extend what had been experimentally observed to a larger time and spatial scale. Therefore, different scenarios were elaborated, regarding soil salinity in relation to particular hypotheses of irrigation management and crop rotation aimed, respectively, at promoting salt leaching and minimize salt load into the soil. This has been done on the basis of historical rain-gauge series reported by the Foggia weather observatory, with reference to the years 1951-2000. Very critical scenarios follow from the performed simulations. If only brackish groundwater is used for irrigation, the annual cultivation of a spring-summer irrigated crop without any additional leaching (apart from rain) leads to a saline buildup. This compromises agricultural soil quality. Therefore, a recommended technical choice is the cultivation of irrigated summer crops not more than once every two years. At the same time, a limited (100-200 mm) but influential fresh water applications for leaching purposes could be usefully associated

Irrigation management in Mediterranean salt affected agriculture: how leaching operates

In the frame of a crop rotation currently applied in a farm of the Apulian Tavoliere (Southern Italy), this paper reports the effect of brackish water irrigation on soil, outlines the corresponding salinity balance, formulates quantitative relations to model salt outflow below the soil root-layer and defines operational criteria to optimize irrigation management at farm level in order to control soil salinity through leaching. The general aim is to contribute to a sustainable use of the available water resources and a proper soil fertility conservation. A three-year trial (2007-2010) was carried out on a farm located close to the coast of the Manfredonia gulf (Mediterranean - Adriatic sea), where irrigation with brackish water is frequently practiced due to seawater intrusion into the groundwater. An especially designed experimental field-unit was set-up: the bottom of three hydraulically insulated plots was covered with a plastic sheet to intercept the percolating water and collect it into tanks by means of drain tubes. Each year a double crop cycle was applied to the soil; a spring-summer crop (tomato, zucchini and pepper, respectively) was followed by a fall-winter crop (spinach, broccoli and wheat). Short "fallow" periods (completely bare soil) were inserted between two crop cycles. Irrigation or rain completely restored crop water consumptions (with the exception of wheat, considered a rainfed crop) and leaching was performed both unintentionally (by rainfalls) or intentionally (supplying higher irrigation volumes whenever the soil electrical conductivity exceeded a fixed threshold). The soil electrical conductivity was periodically measured together with volume and electrical conductivity of irrigation and drainage water. All these measures allowed to draw-up the salt-balance of the soil, respectively at the beginning and the end of each crop cycle. Absolute and relative variations in soil salt content were interpreted with respect to absolute and relative drainage volumes according to a three steps procedure of covariance analysis. A simple, general and comprehensive leaching model is thus presented. Results showed that salt build up into the soil can be very rapid, generally occurring within a single irrigated summer crop cycle. Rainfalls of the autumn-winter period had a crucial role in the removal of salts brought into the soil by summer irrigation. This paper strongly emphasises that additional fresh water supply is of great importance to establish acceptable soil conditions. Two suitable periods for intentional leaching were identified

Cereal straw management: a trade-off between energy and agronomic fate

Climate change mitigation is the most important driving force for bioenergy development. Consequently, the environmental design of bioenergy value chains should address the actual savings of both primary energy demand and greenhouse gases (GHG) emissions. According to the EU Renewable Energy Directive (2009/28/EC), no direct impacts and no GHG emissions should be attributed to crop residues (like cereal straws) when they are removed from agricultural land for the purpose of bioenergy utilisation. The carbon neutral assumption applied to crop residues is, however, a rough simplification. Crop residues, indeed, should not be viewed simply as a waste to be disposed, because they play a critical role in sustaining soil organic matter and therefore have an inherent C-capturing value. Moreover, considering straws as an energy feedstock, its status of co-product is clearly recognised and its availability could be obtained according to different cropping systems, corresponding to different primary energy costs and GHG emissions. This paper highlights some hidden features in the assessment of agricultural energy and carbon balance, still very difficult to be detected and accounted for. Although they are frequently disregarded, these features (such as long term dynamic trend of soil organic carbon and annual nitrous oxide emissions from the soil) should be carefully considered in assembling the energy and emission balance. By using a crop simulation model, the long-term soil organic matter and annual N2O soil emissions were estimated. Consequently, a comprehensive energy and GHG balance was determined in accordance with the life cycle assessment methodology. Contrasting methods of straw management and wheat cultivation were compared: straw retention vs removal from the soil; conventional vs conservation tillage; wheat cropping system as a single-crop or in rotation. The resulting carbon footprint of straws has different magnitudes with respect to the several experimental conditions. By selecting the best agricultural practices, energy from straw can be optimally coupled with grain productions, without detrimental effects on soil fertility. An improved and specifically tailored cropping system is designed to obtain an optimal trade-off

Enhancement of Yield, Phytochemical Content and Biological Activity of a Leafy Vegetable (Beta vulgaris L. var. cycla) by Using Organic Amendments as an Alternative to Chemical Fertilizer

This study evaluates the effect of a chemical fertilizer (ammonium nitrate), a compost (vermicompost from cattle manure) and two biochars (from vine prunings and wood chips, respectively), applied to the soil alone or in mixture, on the yield, phytochemical content and biological activity of Beta vulgaris L. var. cycla (Swiss chard). The respective treatments, each replicated four times, were arranged according to a completely randomized block design. Results showed that vermicompost, both alone and in mixture with vine pruning biochar, significantly increased yield parameters (plant height and leaf area) and yield over the untreated soil and the biochars alone, similar to ammonium nitrate. Moreover, vermicompost, both alone and in mixture, respectively, with the two biochars, determined lower total N and NO3− contents than ammonium nitrate, both alone and in mixture, respectively, with the two biochars. In particular, NO3− content was within the safe thresholds fixed for leafy vegetables by the European Commission to prevent any adverse implication on human health from dietary NO3− exposure. The biochars alone resulted in very low yield and leaf total N content, likely due to a limited release of N for plant uptake, also evidenced by the undetectable NO3− leaf content, similarly shown by plants grown in untreated soil. Vermicompost, alone or in mixture, respectively, with the two biochars, increased the content of specialized metabolites, with a positive effect on antioxidant activity. The organic amendments, particularly compost, could be an alternative to chemical fertilizers to reach a trade-off between yield, nutritional and health qualities in Swiss chard, meeting the needs of farmers and consumers as well as the targets for sustainable food production

Treated agro-industrial wastewater irrigation of tomato crop: Effects on qualitative/quantitative characteristics of production and microbiological properties of the soil

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Effects of treated agro-industrial wastewater irrigation on tomato processing quality

This study was designed to determine the qualitative and microbiological impact of two different sources of irrigation water on tomato fruit: groundwater (GW), as the control, and treated agro-industrial wastewater (SW). The mean tomato fruit quality parameters of dry matter, weight, diameter, colour index, pH, soluble solids content, titratable acidity, Ca2+ and Na+ content were not significantly affected by the different water treatments. Conversely, NO3 – contents was significantly higher with GW use, than with SW (2.21 vs 1.62 mg 100 g–1, respectively; P≤0.05). The microbial quality of the tomato fruit was not significantly different across the GW and SW treatments, with no Salmonella spp. isolated from any of the fruit, and the faecal indicators always below 10 CFU g–1. These data show that agro-industrial treated wastewater can be used for irrigation for industrial tomato production once the long-term effects on the agroecosystem have been defined