Journal of Soil Science and Plant Nutrition

Disease-Suppressive Soils-Beyond Food Production: a Critical Review
Jayaraman S, Naorem AK, Lal R, Dalal RC, Sinha NK, Patra AK and Chaudhari SK
In the pursuit of higher food production and economic growth and increasing population, we have often jeopardized natural resources such as soil, water, vegetation, and biodiversity at an alarming rate. In this process, wider adoption of intensive farming practices, namely changes in land use, imbalanced fertilizer application, minimum addition of organic residue/manure, and non-adoption of site-specific conservation measures, has led to declining in soil health and land degradation in an irreversible manner. In addition, increasing use of pesticides, coupled with soil and water pollution, has led the researchers to search for an environmental-friendly and cost-effective alternatives to controlling soil-borne diseases that are difficult to control, and which significantly limit agricultural productivity. Since the 1960s, disease-suppressive soils (DSS) have been identified and studied around the world. Soil disease suppression is the reduction in the incidence of soil-borne diseases even in the presence of a host plant and inoculum in the soil. The disease-suppressive capacity is mainly attributed to diverse microbial communities present in the soil that could act against soil-borne pathogens in multifaceted ways. The beneficial microorganisms employ some specific functions such as antibiosis, parasitism, competition for resources, and predation. However, there has been increasing evidence on the role of soil abiotic factors that largely influence the disease suppression. The intricate interactions of the soil, plant, and environmental components in a disease triangle make this process complex yet crucial to study to reduce disease incidence. Increasing resistance of the pathogen to presently available chemicals has led to the shift from culturable microbes to unexplored and unculturable microbes. Agricultural management practices such as tillage, fertilization, manures, irrigation, and amendment applications significantly alter the soil physicochemical environment and influence the growth and behaviour of antagonistic microbes. Plant factors such as age, type of crop, and root behaviour of the plant could stimulate or limit the diversity and structure of soil microorganisms in the rhizosphere. Further, identification and in-depth of disease-suppressive soils could lead to the discovery of more beneficial microorganisms with novel anti-microbial and plant promoting traits. To date, several microbial species have been isolated and proposed as key contributors in disease suppression, but the complexities as well as the mechanisms of the microbial and abiotic interactions remain elusive for most of the disease-suppressive soils. Thus, this review critically explores disease-suppressive attributes in soils, mechanisms involved, and biotic and abiotic factors affecting DSS and also briefly reviewing soil microbiome for anti-microbial drugs, in fact, a consequence of DSS phenomenon.
Economically Optimal Rate for Nutrient Application to Maize in the Semi-deciduous Forest Zone of Ghana
Essel B, Abaidoo RC, Opoku A and Ewusi-Mensah N
Low inherent nitrogen (N), phosphorus (P), and potassium (K) contents of smallholder farms limit maize grain yield. Maize grain yield response to N, P, and K mineral fertilizer application and economically optimal rates for nitrogen (EOR), phosphorus (EOR), and potassium (EOR) were evaluated on a Ferric Acrisol within the semi-deciduous forest zone of Ghana. The nutrient rates evaluated were N (0, 30, 60, 90, and 120 kg N ha), P (0, 30, 60, and 90 kg ha PO), and K (0, 30, 60 and 90 kg ha KO). The treatments were arranged in a randomized complete block with three replications using an incomplete factorial design. Nutrient responses were determined using asymptotic quadratic-plus plateau functions. The best nitrogen rate for all P and K levels was 60 kg ha, which gave grain yield of 5 t ha Nitrogen uptake, N agronomic and N recovery efficiencies peaked at 60 kg N ha while N partial factor productivity declined with increasing N application rate. Cost to grain price ratios (CP) were 1.29, 1.65, and 1.65 for N, P, and K, respectively. The EOR was 61 kg ha, 32% less than the recommended 90 kg N ha for maize production in the semi-deciduous forest zone of Ghana. Nitrogen application had the lowest CP ratio, making its application economically profitable than P and K. The findings suggest that the application of N at 61 kg N ha to maize is economically profitable than at higher application rates. However, further studies should be conducted on farmers' fields to validate the results obtained.
Assessment of Biofortification Approaches Used to Improve Micronutrient-Dense Plants That Are a Sustainable Solution to Combat Hidden Hunger
Koç E and Karayiğit B
Malnutrition causes diseases, immune system disorders, deterioration in physical growth, mental development, and learning capacity worldwide. Micronutrient deficiency, known as hidden hunger, is a serious global problem. Biofortification is a cost-effective and sustainable agricultural strategy for increasing the concentrations or bioavailability of essential elements in the edible parts of plants, minimizing the risks of toxic metals, and thus reducing malnutrition. It has the advantage of delivering micronutrient-dense food crops to a large part of the global population, especially poor populations. Agronomic biofortification and biofertilization, traditional plant breeding, and optimized fertilizer applications are more globally accepted methods today; however, genetic biofortification based on genetic engineering such as increasing or manipulating (such as CRISPR-Cas9) the expression of genes that affect the regulation of metal homeostasis and carrier proteins that serve to increase the micronutrient content for higher nutrient concentration and greater productivity or that affect bioavailability is also seen as a promising high-potential strategy in solving this micronutrient deficiency problem. Data that micronutrients can help strengthen the immune system against the COVID-19 pandemic and other diseases has highlighted the importance of tackling micronutrient deficiencies. In this study, biofortification approaches such as plant breeding, agronomic techniques, microbial fertilization, and some genetic and nanotechnological methods used in the fight against micronutrient deficiency worldwide were compiled.
Integrative Soil Application of Humic Acid and Foliar Plant Growth Stimulants Improves Soil Properties and Wheat Yield and Quality in Nutrient-Poor Sandy Soil of a Semiarid Region
Tahoun AMMA, El-Enin MMA, Mancy AG, Sheta MH and Shaaban A
Sandy soils (containing > 50% sand) are widely distributed worldwide and are characterized by their poor structure, low organic matter, weak hydraulic and nutritional properties, and low crop productivity. Using a 2-year pot experiment, in this study, we investigated the effects of humic acid (HA) as a soil amendment and study two plant growth stimulants (PGSs), zinc oxide nanoparticles (ZnONPs), and L-tryptophan (L-TRP), as a foliar application on wheat grown in nutrient-poor sandy soil. Three HA rates (0 (HA), 0.2 (HA), and 0.4 (HA) g kg soil) and five PGS levels [control, 50 mg l (ZnONPs), 100 mg l (ZnONPs), 0.25 mmol l (L-TRP), and 0.5 mmol l (L-TRP)] were used. The soil hydro-physico-chemical properties, morpho-physiological responses, yield, and quality were measured. HA addition amended the soil structure by allowing rapid macroaggregate formation, decreasing bulk density and pH, and increasing porosity and electrical conductivity, thereby improving soil hydraulic properties. HA and HA additions improved growth, yield components, and grain minerals, resulting in higher grain yield by 28.3-54.4%, grain protein by 10.2-13.4%, wet gluten by 18.2-23.3%, and dry gluten by 23.5-29.5%, respectively, than HA. Foliar application of ZnONPs or L-TRP, especially at higher concentrations compared to the control, noticeably recorded the same positive results as HA treatments. The best results were achieved through the integration of HA + ZnONPs or L-TRP to the tested nutrient-poor sandy soil. The interactive application of HA + ZnONPs or L-TRP and the use of mineral fertilizer, which is considered a surplus point in permaculture, can be recommended for sustainable wheat production in nutrient-poor sandy soil.
Global Trends of Acidity in Rainfall and Its Impact on Plants and Soil
Prakash J, Agrawal SB and Agrawal M
Due to its deleterious and large-scale effects on the ecosystem and long-range transboundary nature, acid rain has attracted the attention of scientists and policymakers. Acid rain (AR) is a prominent environmental issue that has emerged in the last hundred years. AR refers to any form of precipitation leading to a reduction in pH to less than 5.6. The prime reasons for AR formation encompass the occurrence of sulfur dioxide (SO), nitrogen oxides (NO), ozone (O), and organic acids in air produced by natural as well as anthropogenic activities. India, the top SO emitter, also shows a continuous increase in NO level responsible for AR formation. The plants being immobile unavoidably get exposed to AR which impacts the natural surrounding negatively. Plants get affected directly by AR due to reductions in growth, productivity, and yield by damaging photosynthetic mechanisms and reproductive organs or indirectly by affecting underground components such as soil and root system. Genes that play important role in plant defense under abiotic stress gets also modulated in response to acid rain. AR induces soil acidification, and disturbs the balance of carbon and nitrogen metabolism, litter properties, and microbial and enzymatic activities. This article overviews the factors contributing to AR, and outlines the past and present trends of rainwater pH across the world, and its effects on plants and soil systems.
Native Plant Species: a Tool for Restoration of Mined Lands
Gairola SU, Bahuguna R and Bhatt SS
The COVID-19 epidemic, food and water insecurity, and the climate emergency have impacted the lives of billions of people worldwide. Ecosystems play a crucial role in tackling these problems. Hence, it is a prime necessity to keep the ecosystems safe and sustainably manage the resources. But this would not suffice for the protection and sustainable management of our surviving natural landscapes and oceans; we also need to restore the planet's devastated ecosystems and the enormous benefits they give. Mining exerts a lot of pressure on the land resources further depleting the fertility of the soil. The overburdened dumps are devoid of the nutrients which turns natural succession at a slow pace. The restoration of the degraded mined areas is essential to re-establish the ecological balance so that a self-sustaining ecosystem can be maintained. The plantation of selected species of plants could be a sustainable and organic tool for the restoration of the degraded mined land. In today's context, various ways regarding ecological restoration are suggested, but the native plant species plantation is the best tool for restoring the degraded land at a quicker pace. The present paper reviews the importance of the native plant species and their efficacy in restoring degraded mined land based on area and time of succession and climax.
Foliar Application of Iron Oxide Nanoparticles Promotes Growth, Mineral Contents, and Medicinal Qualities of L
Ahmed MA, Shafiei-Masouleh SS, Mohsin RM and Salih ZK
Goldenrod ( L.) is considered for their medicinal properties for humans. These properties are attributed to some volatile compounds that can be extracted from above- and underground organs of plants. More ingredients of medicinal plants are undoubtedly considered by herbal medicine activists. The study aimed to promote yield and quality under foliar application of FeO nanoparticles that can be considered as a safe and healthy fertilizer on the basis of US Food and Drug Administration (FDA) regulatory process about color additives. The experiment was performed with concentrations of FeO nanoparticles (0, 0.5, or 1 mg L) and foliar application times (1, 2, 3, 4, or 5 times) on 4- to 5-leaf plants of . Results showed that 4 times foliar application of 1 mg L caused the best plant growth and mineral element contents (nitrogen, phosphorous, potassium, copper, and zinc) except for Fe content that the more the times of foliar application, the more the Fe content increased. However, the flavonoid (rutin and quercetin) and essential oils (caryophyllene, alpha-pinene, camphene, limonene, linalool, myrcene, and terpinene) as biochemical and medicinal qualities of the treated plants were remarkably promoted when 1 mg L of nanoparticles was sprayed 5 times. Furthermore, the more the element contents, the more the ingredients. Finally, based on the goals of herbal medicine activists for the production of the essence, extract, or herb, both 5 and 4 times of foliar applications of ferric oxide nanoparticles are safe and may be economic and recommendable.