Although development of low (extensive) and high (intensive) maintenance green roof systems has progressed significantly, studies on the function of the growing substrate as a living constituent are lacking. The objective of this review paper is to summarize current scientific knowledge on the components, composition, and characteristics of green roof substrates and to identify future research needs. Due to variations in climate and desired plant types, there is no universal growing substrate. An appropriate substrate is expected to provide permanent physical support for plants and possess a fine balance between free drainage and adequate plant available water and nutrient retention. Typical substrate components include minerals in natural or modified forms such as sand, lava rock, or expanded shale, clay and slate; recycled waste materials like crushed bricks or tiles, crushed or aerated concrete and subsoil; stabilized organic matter such as composts; and plastic materials and slow release fertilizers. Proportions of components vary among substrates based on target vegetation, green roof type, and other considerations. Better green roof management for maximum benefits will require characterizing, quantifying and understanding the impacts of plant species and building attributes such as aspect, slope, height and heating on substrate performance, and should be considered for future research.

Small-scale vegetable and fruit crop producers in the USA use locally available commercial organic fertilizers and soil amendments recycled from municipal and agricultural wastes. Organic soil amendments provide crops with their nutrient needs and maintain soil health by modifying its physical, chemical, and biological properties. However, organic soil amendments might add unwanted elements such as toxic heavy metals or salts, which might inhibit crop growth and reduce yield. Therefore, the objective of this study was to evaluate phytotoxicity of three commercial organic amendments, chicken manure, milorganite, and dairy manure, to collard greens using the seed germination bioassay and chemical analysis of the organic amendments. The seed germination bioassay was conducted by incubating collard greens seeds to germinate in 1:10 ( w / v ) organic amendment aqueous extracts. Results of this work identified phytotoxic effects of chicken manure and milorganite, but not dairy manure, to collard greens. Potentially phytotoxic chemicals such as copper, zinc, nickel, and salts were also higher in chicken manure and milorganite compared to dairy manure. In particular, nickel in chicken manure and milorganite aqueous extracts was 28-fold and 21-fold, respectively, higher than previously reported toxic levels to wheat seedlings. The results demonstrate the need for more research on phytotoxicity of commercial organic soil amendments to ensure their safe use in vegetable and fruit crop production systems.

No abstract

As the world’s population is increasing exponentially, human diets have changed to less healthy foods resulting in detrimental health complications. Increasing vegetable intake by both rural and urban dwellers can help address this issue. However, these communities often face the challenge of limited vegetable supply and accessibility. More so, open field vegetable production cannot supply all the vegetable needs because biotic and abiotic stress factors often hinder production. Alternative approaches such as vegetable production in greenhouses, indoor farms, high tunnels, and screenhouses can help fill the gap in the supply chain. These alternative production methods provide opportunities to use less resources such as land space, pesticide, and water. They also make possible the control of production factors such as temperature, relative humidity, and carbon dioxide, as well as extension of the growing season. Some of these production systems also make the supply and distribution of nutrients to crops easier and more uniform to enhance crop growth and yield. This paper reviews these alternative vegetable production approaches which include hydroponics, aeroponics, aquaponics and soilless mixes to reveal the need for exploring them further to increase crop production. The paper also discusses facilities used, plant growth factors, current challenges including energy costs and prospects.

Lack of essential amino acids (EAA) in the diet of at-risk populations could beget a state of food insecurity. Plant proteins are deficient in some essential amino acids. Animals obtain EAA from plant sources. Simple biotechnologies are being developed for improving the EAA composition of crop proteins. The aim was to integrate-discriminate glycolysis and citric-glyoxylic acid cycles to optimize biosynthesis of EAA in food crops. Permutation of diverse metabolic pathways at the mRNA level by glutamate dehydrogenase (GDH)-synthesized RNA is a common biotechnology for doubling the nutritious compositions of plants. Peanuts were planted in plots and treated with mineral salts mixed according to stoichiometric ratios. Protein-bounded and free amino acids of mature peanut seeds were determined by HPLC. GDH-synthesized RNA probes homologous to the mRNAs encoding glyceraldehyde-3-phosphate dehydrogenase (GAPDH), phosphoglycerate mutase (PGlycM), phosphoenolpyruvate carboxylase (PEPCase), enolase, malate dehydrogenase (MDH), isocitrate lyase (ICL), and malate synthase (MS) were prepared from peanut seeds using restriction fragment double differential display PCR method. Northern assays of peanut total RNA showed that the mRNAs encoding PGlycM, PEPCase, MDH, and MS shared extensive sequence homologies that produced a dense network of cross-talks, resulting to co-differential silencing of the mRNAs thereby permuting glycolysis, citric-glyoxylic acid cycles. There were 42 permutations in the NPPKtreated, 105 in control, 420 in KN-, and NPKS-treated peanuts. Because of permutations involving the mRNAs encoding ICL and MS, wherever the abundances of these mRNAs were high (control, and NPPK-treated peanuts) the concentrations of the α-ketoglutarate group of total glutamate, glutamine, arginine, proline, and histidine were minimized (<7.0 mg/g) but the concentrations of the oxaloacetate group of total aspartate, lysine, methionine, threonine, and isoleucine were maxi-* Corresponding author. G. O. Osuji et al.3092 mized (>28.0 mg/g). The integration of glycolysis, citric and glyoxylic acid cycles increased the quality and doubled the concentrations of the protein-bounded EAA composition of NPPK-treated (33.37 mg/g) compared with the control peanut (15.66 mg/g). The commanding biotechnology was the stoichiometric mineral salts-based induction of GDH to synthesize the RNAs that integrated glycolysis, citric-glyoxylic acid cycles to one functional unit.