Heavy metals are among the most important sorts of contaminant in the environment. Several methods already used to clean up the environment from these kinds of contaminants, but most of them are costly and difficult to get optimum results. Currently, phytoremediation is an effective and affordable technological solution used to extract or remove inactive metals and metal pollutants from contaminated soil and water. This technology is environmental friendly and potentially cost effective. This paper aims to compile some information about heavy metals of arsenic, lead, and mercury (As, Pb, and Hg) sources, effects and their treatment. It also reviews deeply about phytoremediation technology, including the heavy metal uptake mechanisms and several research studies associated about the topics. Additionally, it describes several sources and the effects of As, Pb, and Hg on the environment, the advantages of this kind of technology for reducing them, and also heavy metal uptake mechanisms in phytoremediation technology as well as the factors affecting the uptake mechanisms. Some recommended plants which are commonly used in phytoremediation and their capability to reduce the contaminant are also reported.

/pdf/a-review-on-heavy-metals-as-pb-and-hg-uptake-by-plants-2mz87idda6.pdf

A Review on Heavy Metals (As, Pb, and Hg) Uptake by Plants through Phytoremediation

Nitrogen is the most limiting nutrient for crop production in many of the world's agricultural areas and its efficient use is important for the economic sustainability of cropping systems Furthermore, the dynamic nature of N and its propensity for loss from soil‐plant systems creates a unique and challenging environment for its efficient management Crop response to applied N and use efficiency are important criteria for evaluating crop N requirements for maximum economic yield Recovery of N in crop plants is usually less than 50% worldwide Low recovery of N in annual crop is associated with its loss by volatilization, leaching, surface runoff, denitrification, and plant canopy Low recovery of N is not only responsible for higher cost of crop production, but also for environmental pollution Hence, improving N use efficiency (NUE) is desirable to improve crop yields, reducing cost of production, and maintaining environmental quality To improve N efficiency in agriculture, integrated N management strategies that take into consideration improved fertilizer along with soil and crop management practices are necessary Including livestock production with cropping offers one of the best opportunities to improve NUE Synchrony of N supply with crop demand is essential in order to ensure adequate quantity of uptake and utilization and optimum yield This paper discusses N dynamics in soil‐plant systems, and outlines management options for enhancing N use by annual crops

Enhancing nitrogen use efficiency in crop plants

/pdf/conservation-agriculture-and-ecosystem-services-an-overview-5dh4ewvhue.pdf

Conservation agriculture and ecosystem services: An overview

Phytoremediation: Environmentally sustainable way for reclamation of heavy metal polluted soils.

Cereal production that now sustains a world population of more than 6.5 billion has tripled during the past 40 yr, concurrent with an increase from 12 to 104 Tg yr(-1) of synthetic N applied largely in ammoniacal fertilizers. These fertilizers have been managed as a cost-effective form of insurance against low yields, without regard to the inherent effect of mineral N in promoting microbial C utilization. Such an effect is consistent with a net loss of soil organic C recently observed for the Morrow Plots, America's oldest experiment field, after 40 to 50 yr of synthetic N fertilization that substantially exceeded grain N removal. A similar decline in total soil N is reported herein for the same site and would be expected from the predominantly organic occurrence of soil N. This decline is in agreement with numerous long-term baseline data sets from chemical-based cropping systems involving a wide variety of soils, geographic regions, and tillage practices. The loss of organic N decreases soil productivity and the agronomic efficiency (kg grain kg(-1) N) of fertilizer N and has been implicated in widespread reports of yield stagnation or even decline for grain production in Asia. A major global evaluation of current cereal production systems should be undertaken, with a view toward using scientific and technological advances to increase input efficiencies. As one aspect of this strategy, the input of ammoniacal N should be more accurately matched to crop N requirement. Long-term sustainability may require agricultural diversification involving a gradual transition from intensive synthetic N inputs to legume-based crop rotations.

https://www.mudcitypress.com/PDF/mulvaney.pdf

Synthetic nitrogen fertilizers deplete soil nitrogen: a global dilemma for sustainable cereal production.

The combined long-term effects of tillage method, crop rotation, and N fertilizer rates on grain yield have not been studied in rainfed systems under Mediterranean climates. As part of a long-term experiment started in 1986, a field study was conducted between 1994 and 1998 to determine the effects of tillage (TILL), crop rotation (ROT), and N fertilization on wheat (Triticum aestivum L.) growth and yield in a rainfed Mediterranean region. Tillage treatments included no tillage (NT) and conventional tillage (CT). Crop rotations were wheat-sunflower (Helianthus annuus L.) (WS), wheat-chickpea (Cicerarietinum L.) (WCP), wheat-faba bean (Vicia faba L.) (WFB), wheatfallow (WF), and continuous wheat (CW). Nitrogen fertilizer rates were 0, 50, 100, and 150 kg N ha -1 on a Vertisol (Typic Haploxerert). A split-split plot design with four replications was used. Heavy rainfall during this research negatively impacted vegetative growth and grain yield of the wheat due to waterlogging. Wheat yield in the wet years was lower under NT than under CT. Yield decreased in the following crop rotation sequence: WFB » WF > WS > WCP » CW. Wheat responded to N fertilizer at rates up to 100 kg N ha -1 in the wet years but exhibited no response in the dry years. Yield under CT was higher at all N rate applied to wheat. The effect of N fertilizer on yield was more marked for the rotations with no legumes. The incorporation of the results for the 4-yr period to those of the long-term experiment provides more consistent information on the characterization and performance of the various systems.

Effects of Tillage, Crop Rotation, and Nitrogen Fertilization on Wheat under Rainfed Mediterranean Conditions

Effects of long-term tillage, crop rotation and nitrogen fertilization on bread-making quality of hard red spring wheat

Competition, growth and yield of faba bean (Vicia faba L.)

Efficient N fertilizer management is critical for the economic production of wheat and the long-term protection of environmental quality. A 3-yr field experiment on a rainfed Vertisol was designed to study the effects of N fertilizer timing on the efficiency of N in durum wheat (Triticum turgidum L. var. durum Desf.). A single rate of 150 kg N ha -1 was used with different fractions being applied at planting, tillering, and stem elongation. A 15 N experiment was also conducted within the main experiment area, with microplots, to quantify N uptake from fertilizer and soil. Mean wheat recovery of N fertilizer ranged from 12.7% when applied at sowing to 41.6% when applied as a topdressing at the beginning of stem elongation. The mean annual contribution of soil residual N and mineralization was 167 kg N ha -1 , representing a considerable proportion of total wheat N uptake-ranging from 80.4% when N fertilizer was applied in the fall to 56.3% when it was applied at stem elongation. This would account for the poor and inconsistent response of grain yield and N efficiency indices, and for the importance of soil N in Vertisols for predicting wheat N fertilizer requirements, due to the carryover effect. It is recommended that N fertilizer be applied mainly as a topdressing in durum wheat, between tillering and stem elongation, to enhance crop N use efficiency (NUE) and reduce losses through leaching and runoff.

Francisco J. López-Bellido

Papers

Effects of Tillage, Crop Rotation, and Nitrogen Fertilization on Wheat under Rainfed Mediterranean Conditions

Effects of long-term tillage, crop rotation and nitrogen fertilization on bread-making quality of hard red spring wheat

Competition, growth and yield of faba bean (Vicia faba L.)

Fertilizer Nitrogen Efficiency in Durum Wheat under Rainfed Mediterranean Conditions: Effect of Split Application

Carbon Sequestration by Tillage, Rotation, and Nitrogen Fertilization in a Mediterranean Vertisol