Clorose férrica induzida pelo calcário

Iron chlorosis is one of the most common and difficult to control problems in crops grown on calcareous soils. In alkaline soils, which represent one third of the Earth surface, the bicarbonate ion prevails and is a major induction factor of iron chlorosis. As a result, alkalinity limits Fe bioavailability in the soil solution, Fe reduction and assimilation, as well as transport and uptake within the plant. Due to this nutritional imbalance, plants develop different response strategies which are not entirely successful on calcareous soils. In consequence, yield, fruit quality and harvesting season are negatively affected. Preventing and treating iron chlorosis is highly costly, but is inevitable, in order to ensure crop sustainability in regions where soil calcium carbonate and aridity are limiting factors. In this work, we present a short overview of Fe dynamics in calcareous soils and its influence on crop productivit

Advances in research on the use of biochar in soil for remediation: a review

Purpose: Soil contamination mainly from human activities remains a major environmental problem in the contemporary world. Significant work has been undertaken to position biochar as a readily-available material useful for the management of contaminants in various environmental media notably soil. Here, we review the increasing research on the use of biochar in soil for the remediation of some organic and inorganic contaminants.  Materials and methods: Bibliometric analysis was carried out within the past 10 years to determine the increasing trend in research related to biochar in soil for contaminant remediation. Five exemplar contaminants were reviewed in both laboratory and field-based studies. These included two inorganic (i.e., As and Pb) and three organic classes (i.e., sulfamethoxazole, atrazine, and PAHs). The contaminants were selected based on bibliometric data and as representatives of their various contaminant classes. For example, As and Pb are potentially toxic elements (anionic and cationic, respectively), while sulfamethoxazole, atrazine, and PAHs represent antibiotics, herbicides, and hydrocarbons, respectively.  Results and discussion: The interaction between biochar and contaminants in soil is largely driven by biochar precursor material and pyrolysis temperature as well as some characteristics of the contaminants such as octanol-water partition coefficient (KOW) and polarity. The structural and chemical characteristics of biochar in turn determine the major sorption mechanisms and define biochar’s suitability for contaminant sorption. Based on the reviewed literature, a soil treatment plan is suggested to guide the application of biochar in various soil types (paddy soils, brownfield, and mine soils) at different pH levels (4–5.5) and contaminant concentrations ( 50 mg kg−1).  Conclusions: Research on biochar has grown over the years with significant focus on its properties, and how these affect biochar’s ability to immobilize organic and inorganic contaminants in soil. Few of these studies have been field-based. More studies with greater focus on field-based soil remediation are therefore required to fully understand the behavior of biochar under natural circumstances. Other recommendations are made aimed at stimulating future research in areas where significant knowledge gaps exist

Organic acids metabolism in roots of grapevine rootstocks under severe iron deficiency

Background and aims In many important viticultural areas of the Mediterranean basin, plants often face prolonged periods of scarce iron (Fe) availability in the soil.The objective of the present work was to perform a comparative analysis of physiological and biochemical responses of Vitis genotypes tosevere Fe deficiency. Methods Three grapevine rootstocks differing in susceptibility to Fe chlorosis were grown with and without Fe in the nutrient solution. Results Rootstock 101-14, susceptible to Fe chlorosis, responded to severe Fe deficiency by reducing the root activity of phosphoenolpyruvate carboxylase (PEPC) and malate dehydrogenase(MDH),however,itaccumulated high levels of citric acid. By contrast, rootstock 110 Richter, tolerant to Fe chlorosis, maintained an activemetabolismoforganicacids,butcitricacidaccumulationwaslowerthanin101-14.Similarlyto101-14, rootstock SO4 showed a strong decrease in PEPC and MDH activities. Nevertheless it maintained moderate citric acid levels in the roots, mimicking the response by 110 Richter. Conclusions Root PEPC and MDH activities can be used as tools for screening Fe chlorosis tolerance. Conversely, organic acids accumulation in roots may not be a reliable indicator of Fe chlorosis tolerance, particularly under conditions of severe Fe deficiency, because of their probable exudation by roots.Our results show that drawing sound conclusions from screening programs involving Fe deficiency tolerance requires short as well as long-term assessment of responses to Fe deprivation

Iron nutrition of fruit tree crops

Although iron (Fe) needs by fruit trees are relatively low, Fe deficiency represents the main constraint for successful cultivation of fruit tree crops in calcareous and alkaline soils. Kiwifruit, peach and pear, several Citrus and Vaccinium spp. are very susceptible to Fe chlorosis, cherry and grape are relatively susceptible and apple is relatively tolerant. The typical Fe deficiency symptoms, the interveinal leaf yellowing starting from apical leaves which may progress and turn into necrosis, exhibit a temporal and spatial variability, requiring an efficient diagnosis systems. Iron deficiency reduces yields and fruit quality and forces growers to adopt measures for controlling and preventing the development of Fe chlorosis. The most widely adopted Fe fertilizers are the synthetic chelates, that do not represent a sustainable management approach, due to the cost and their potential pollution of the soil and water environments. The genetic approach to prevent chlorosis is based on the choice of tolerant rootstocks, which are known to activate mechanisms for improving Fe uptake under condition of low Fe availability. Unfortunately, for several fruit crops iron tolerant rootstocks have some adverse agronomic characteristics (e.g. excessive vigor) which make their adoption unlikely in modern fruit industry. Alternatives to Fe chelates have been identified and need to be tested and adapted to different conditions: they should aim at the improvement of soil environment for root growth and activity and/or to the enhancement of Fe availability in the soil and in the tree