Maize Yield Response, Root Distribution and Soil Desiccation Crack Features as Affected by Row Spacing.

Plant density is among the most critical factors affecting plant yields and resource use efficiency since it drives the exploitation of the available resources per unit area, root distribution and soil water losses by direct evaporation from the soil. Consequently, in fine-textured soils, it can also affect the formation and development of desiccation cracks. The aim of this study, carried out on a sandy clay loam soil in a typical Mediterranean environment, was to investigate the effects of different row spacings of maize (Zea mais L.) on yield response, root distribution and the main features of desiccation cracks. The field experiment compared bare soil and soil cropped with maize using three plant densities (6, 4 and 3 plants m-2), obtained by keeping the number of plants in a row constant and varying the distance between the rows (0.5-0.75-1.0 m). The highest kernel yield (16.57 Mg ha-1) was obtained with the greatest planting density (6 plants m-2) with a row spacing of 0.5 m; significantly lower yields were recorded with spacings of 0.75 and 1 m, with a decrease of 8.09% and 18.24%, respectively. At the end of the growing season, soil moisture in the bare soil was on average 4% greater in comparison to the cropped soil and was also affected by row spacing, decreasing with the decrease in the inter-row distance. An inverse behaviour was observed between soil moisture and both root density and desiccation crack size. Root density decreased to the increase in soil depth and to the increase in distance from the row. The pluviometric regime occurred during the growing season (total rainfall of 343 mm)-resulted in the formation of cracks of reduced size and with an isotropic behaviour in the bare soil, whereas in the cultivated soil, the cracks were parallel to the maize rows and increased in size with decreasing inter-row distance. The total volume of the soil cracks reached a value of 135.65 m3 ha-1 in the soil cropped with a row distance of 0.5 m, and was about ten times greater in comparison to the bare soil and three times greater in comparison to a row spacing of 1 m. Such a volume would allow a recharge of 14 mm in the case of intense rainy events on soil characterised by low permeability.

Plant mineral nutrition and disease resistance: A significant linkage for sustainable crop protection.

Complete and balanced nutrition has always been the first line of plant defense due to the direct involvement of mineral elements in plant protection. Mineral elements affect plant health directly by modulating the activity of redox enzymes or improving the plant vigor indirectly by altering root exudates, and changing microflora population dynamics, rhizosphere soil nutrient content, pH fluctuation, lignin deposition, and phytoalexin biosynthesis. Nitrogen (N) is one of the most important macronutrients having a significant impact on the host-pathogen axis. N negatively affects the plant's physical defense along with the production of antimicrobial compounds, but it significantly alleviates defense-related enzyme levels that can eventually assist in systemic resistance. Potassium (K) is an essential plant nutrient, when it is present in adequate concentration, it can certainly increase the plant's polyphenolic concentrations, which play a critical role in the defense mechanism. Although no distinguished role of phosphorus (P) is observed in plant disease resistance, a high P content may increase the plant's susceptibility toward the invader. Manganese (Mn) is one of the most important micronutrients, which have a vital effect on photosynthesis, lignin biosynthesis, and other plant metabolic functions. Zinc (Zn) is a part of enzymes that are involved in auxin synthesis, infectivity, phytotoxin, and mycotoxin production in pathogenic microorganisms. Similarly, many other nutrients also have variable effects on enhancing or decreasing the host susceptibility toward disease onset and progression, thereby making integrative plant nutrition an indispensable component of sustainable agriculture. However, there are still many factors influencing the triple interaction of host-pathogen-mineral elements, which are not yet unraveled. Thereby, the present review has summarized the recent progress regarding the use of macro- and micronutrients in sustainable agriculture and their role in plant disease resistance.

Defense Inducers Mediated Mitigation of Bacterial Canker in Tomato through Alteration in Oxidative Stress Markers.

The bacterial canker disease of tomato caused by Clavibacter michiganensis subsp. michiganensis (Cmm) has been reported to adversely affect the tomato cultivation in the NE hilly regions of India. Defense inducers such as salicylic acid (SA), isonicotinic acid (INA), benzothiadiazole (BTH) and lysozyme were used as prophylactic and curative sprays at different concentrations to test their efficacy in inducing resistance in tomato plants against Cmm under protected conditions. The induced resistance was studied through the alteration in the activities of oxidative stress marker enzymes (PAL, PO, PPO, TPC and PR-2 protein), hydrogen peroxide formation in leaf tissues and lignin accumulation in stem tissues, as well as through the reduction in disease severity under glasshouse conditions. The results of the present study revealed that the enzymatic activity, hydrogen peroxide formation and lignin production were significantly higher in the BTH (500 ppm)-treated leaves than in those observed in the control. The lowest disease incidence was recorded when BTH was applied as a prophylactic spray (27.88%) in comparison to being applied as a curative spray (53.62%), thereby suggesting that a defense inducer, BTH, shows antibacterial activity against Cmm, reduces disease incidence severity and induces defense responses in the tomato plant.

Agricultural waste recycling in horticultural intensive farming systems by on-farm composting and compost-based tea application improves soil quality and plant health: A review under the perspective of a circular economy.

The vegetables supply chain of intensive farming systems has gained huge relevance due to environmental pollution, residual toxicity towards microorganisms and humans, development of plant pathogen resistance, biodiversity loss, and hazard to human health. Studies addressed to clean from misuse of plant fungicides, soil fumigants, and fertilizers have encouraged the search of eco-friendly alternatives. This paper aims to give deeper understand of new insights for on-farm composting and compost-based tea application for soil and plant through the virtuous reuse of agricultural waste. On-farm composting is viable option thanks to benefits on soil quality and plant health which valorize underused biomass. This paper critically discusses and compares the most promising technologies in order to recycle in situ residual biomass into high-value added products for soil amendment (compost) and plant treatment (compost-based tea). Compost contains minerals, heavy metals, humic substances, and endogenous microorganisms to improve soil quality. Compost application had many benefits against plant pathogens and diseases due to innovative tailored formulates. Compost can be employed either alone or in combination with exogenous microbial consortia (protists, fungi, oomycetes, yeast, actinomycetes, and bacteria) acting as biological control agents by fitting the agrochemical market requirements for improving soil quality and plant health. Liquid formulations made of crude compost-based teas and/or tailored mixtures of humic acids, fulvic acids, humin, macro-micronutrients, and endogenous microbiota have many benefits for plant growth and crop health. Nonetheless, the complex European regulations and national laws, manure surplus, variability in availability and transporting of compost, variability in compost quality and feedstock composition, greenhouse gas emissions, and energy requirement were very hard barriers for on-farm composting and compost derivatives application. Recommendations, novelties, innovations, sustainability, and directions of future researches that may help to solve a number of these issues under the new perspective of a circular economy system were presented and discussed.

Improving the shelf-life and quality of fresh and minimally-processed fruits and vegetables for a modern food industry: A comprehensive critical review from the traditional technologies into the most promising advancements.

The market size of fresh and minimally-processed fruits and vegetables (MPFVs) have grown rapidly in the last years as a result of consumer attitudes change due to their increasing use in prepared mixed salad for fresh, healthy and convenient food. Handling and mechanical operations of cutting and peeling induce injures and release of on-site cellular contents which promote the growth of harmful microbes. Chlorine has been widely adopted in fresh and MPFVs disinfection in washing due to its low cost and high efficacy against a broad spectrum of microorganisms; but, continuous replenishment of chlorine into high organic wash water can promote the formation of suspected carcinogenic compounds. There is a real need to find new alternatives to chlorine to preserve MPFVs quality for longer time. Although several methods and chemicals can be used to achieve similar reduction of microorganism counts without the production of harmful compounds, nor compromising the quality of MPFVs produce, fewer amount of them have gained widespread acceptance by the food industry. The challenge of this work was to give an upgraded level of understanding for producers and retailers to underpin future research directions for a modern food industry in order to resolve existing issues that limit fresh-cut quality and shelf-life. This paper covers a comprehensive review to improve shelf-life and quality of MPFVs, from the traditional technologies toward the most promising advancements.