Journal of Soil Science and Plant Nutrition

As a vital micronutrient, zinc is essential for the optimal growth of plants that can be released from insoluble compounds by zinc-solubilizing fungi. This study aimed to investigate the efficiency of indigenous fungi in accumulation, bioconcentration, and translocation of zinc in wheat through two in vitro and greenhouse phases. In first experiment, several indigenous fungi (Trichoderma harzianum, T. longibrachiatum, Aspergillus niger, and A. ustus) were isolated from an industrial polluted area with heavy metals and screened for their ability to grow under various zinc-sulfate concentrations. Results revealed that Aspergillus spp. grew more slowly than T. harzianum which showed the maximum tolerance index than others, whereas other fungal growth was inhibited. The greenhouse phase was conducted as a factorial experiment in a completely randomized design with three replicates. Experimental factors included fungal treatments at three levels (control, inoculation with T. longibrachiatum, and A. niger), and the fungi were screened based on their superior performance in the in vitro phase and zinc sulfate application at four levels (0, 60, 300, and 600 mg L−1). Root accumulation increased at higher zinc concentration (600 mg kg−1) in wheat inoculated with T. longibrachiatum by 24% over the control. By contrast, bioconcentation factor and zinc translocation to roots and grains of inoculated plants reduced significantly under zinc concentrations by 80% and 62%. Overall, this study strengthens the idea that inoculation zinc-solubilizing strains has the potential to boost growth and could be used as bioinoculants, particularly with Trichoderma spp. for wheat biofortification addressing the nutritional issues in both plants and humans.

Phosphorus (P) will be exhausted, and its recovery and cycling will play a pivotal role in agricultural systems. Different technologies have been developed to recover P from waste materials, such as mono-incineration, acid digestion, and coprecipitation of P from wastewaters. The aim of this study was to assess the plant availability of P from different recycled P products by using a sequential chemical P fractionation of soil P and to study the fate of P applied to the soil. We evaluated the plant P availability in soils fertilized with eight recycled P products in comparison with two commercial fertilizers (triple superphosphate [TSP] and rock phosphate [Rock-P]) by means of a sequential chemical extraction of soil P and combined this data with previously published information for soil isotopically exchangeable P (IEP) and P uptake by plants (PU). We sequentially extracted inorganic P with alkaline extractants and an acid solution and analyzed the increase in P fractions caused by the application of different fertilizers. P extracted by alkali solutions was positively correlated with the IEP and with PU, whereas P extracted by the acid solution was negatively correlated with these parameters. In soils fertilized with recycled P products obtained by a chemical procedure (magnesium-ammonium-phosphate), soil P was extracted mainly by alkali extractants, while in soils fertilized with P products obtained by thermal procedures (i.e. sewage sludge ashes), soil P was extracted by the acid solution and was of low plant availability. Sequential chemical fractionation of soil P is suitable for characterizing the plant availability of P from recycled P products. The increase in the alkali soluble fraction in soil characterizes the portion of P available to plants, while the acid soluble fraction characterizes the recalcitrant portion. Phosphorus from fertilizers obtained by chemical procedures, like magnesium-ammonium-phosphate, is mainly extracted by alkali solutions and is comparable to water-soluble P fertilizers, while P from products obtained by thermal processes is mainly extracted by acid solutions and remains mostly unavailable to plants.

A study was carried out to explore soil bacterial diversity associated with Himalayan Alder (Alnus nepalensis)-based shifting cultivation system in Khonoma Village, Nagaland. This agricultural system is well known for its traditional and sustainable form of shifting cultivation and natural biodiversity conservation in the Eastern Himalayan region of India. Surface soil samples (0–30 cm) were collected from alder-based crop fields in Khonoma, Nagaland, and brought to the laboratory for soil nutrient analysis and isolation of culturable bacteria. Standard methodologies were followed for soil nutrient and bacterial diversity analysis. Isolated bacteria were identified using 16S rDNA spacer sequence analysis. BLAST and phylogenetic analysis of molecular sequences identified a unique bacterial isolate in the soil. 16S rDNA partial sequencing of this bacterial strain showed 99% similarity with Kosakonia sacchari–type strain SP1T which has been named for its association with sugarcane. K. sacchari KhAn is a free-living, aerobic, gram-negative, non-spore-forming, and motile rod-shaped bacterium. This bacterial strain holds diazotrophic potential as it was able to grow in nitrogen-free medium and positive for nifH amplification. Furthermore, it showed positive test for ammonia production in peptone water. The soil under alder-based farming system was rich in organic carbon (3.60 ± 0.17%), available nitrogen (536.67 ± 9.28 kg ha−1), available phosphorous (77.35 ± 4.19 kg ha−1), and exchangeable potassium 127.88 ± 10.62 kg ha−1. The existing literature revealed that K. sacchari has not been reported from India until now; therefore, this is the first novel report from India. This contribution represents Eastern Himalaya, a Biodiversity hotspot of the country.

We studied the effect of fertigation with cattle slurry on native and exotic arboreal tree species in Chile. The objectives were to identify the most promising species for buffer strips to mitigate the stream pollution in dairy facilities, to determine where most nutrients accumulate (leaves, stems, or roots), and to test whether the native species are or are not a better biofilter than the exotic ones. We hypothesized that the individuals that were fertilized would have a higher nutrient concentration, nutrient accumulation, and growth than those non-fertilized. N and K concentrations were similar in fertilized trees and in the controls, while the P, Ca, Mg, and Na concentrations were higher in the control than those in the fertilized trees. Most species responded positively to fertilization on a dry matter basis. Luma apiculata, Drimys winteri, and Blepharocalyx cruckshanksii responded to fertilization showing a greater height and diameter growth. Generally, nutrients accumulated in leaves. Overall, the exotic Eucalyptus nitens was the species that accumulated more nutrients given its large growth rate. The native species that more commonly stood out in this study were D. winteri, Nothofagus dombeyi, and L. apiculata. In general, a minor proportion of the applied slurry was absorbed by trees, and we recommend the use of trees in biofilters as a complement to crop and pasture absorption.

The present study investigated the quality of soil organic matter (SOM) and carbon (C) stability in saline and sodic soils under rice–wheat cropping system in south-western Punjab (India). The main objective of this study was to evaluate the impact of salt-affected landscapes on soil physical, chemical, biological, and microbial attributes which inter alia influence SOM quality and vice versa. The C stability in soils under saline and sodic landscapes was studied vis-à-vis normal soils based on clay dispersion ratio (CDR), clay flocculation index (CFI), distribution of macro- (> 0.25 mm) and micro-aggregates (< 0.25 mm), aggregate ratio (AR), C preservation capacity (CPC), total organic C (TOC) fractions of variable oxidizability, and partitioning of SOM as humic acid (HA), non-humic acid (NH), and fulvic acid (FA). Soil enzymatic activity, C mineralization, and basal soil respiration (BSR) were determined to estimate microbial (qmic) and mineralization quotients (qM) for soils under salt-affected landscapes. Soil-related glomalin protein (TG) was determined to establish relationship between aggregate breakage and eventually the release of C. Sodic landscapes had significantly (p < 0.05) higher CDR (by ~ 17.6 and 12.6%) but lower CFI (by ~ 25.0 and 17.2%) than saline and normal landscapes, respectively. The AR was significantly lower by ~ 28.8% and 50.9% in saline and sodic, compared with the normal landscapes. The salt-affected soils had significantly lower NH, HA, and FA concentration than the normal soils. The stable C pool comprised ~ 69.9% of TOC in saline as compared to ~ 55.1% in sodic and ~ 66.1% in normal landscapes. Macro-aggregate breakage and C release was related to decreased TG content and was discernible as significant reduction in aggregate associated C and CPC in sodic soils. A significantly higher qM for normal soils (by ~ 8.1% of TOC) than saline (by ~ 4.5%) and sodic soils (~ 5.3%) was responsible for higher C mineralization and BSR in soils. These results revealed that loss of TOC pool in sodic soils was ascribed to significantly higher dispersion ratio (DR) because of increased WDS and WDC causing reduction in proportion of water stable aggregates (WSA). Aggregate breakage in sodic soils resulted in loss of stable C pool with concomitant increase the active C pool. The lower qmic for soils under salt-affected landscapes revealed stressed microbial biomass due to excessive salt accumulation. The study highlights great potential for increasing SOM stabilization and structural stability of salt-affected soil with the adoption of appropriate land-use management strategies. These results underpin considerable potential for C sequestration in salt-affected soils through land rehabilitation by reclamation.

Plants can generate and release allelochemicals into soils under environmental stresses to compete for resources and to combat pathogens and parasites. The frequent rotation of cultivated land and the high-density cropping may result in the accumulation of allelochemicals, resulting in obstacles to continuous cropping. Biochar has been proven to improve soil quality, which can potentially reduce the formation of allelochemicals by plants, alleviating allelopathy. In this study, the formation of an allelochemical substance benzoic acid (BA), the growth indicators, and root lipid peroxidation of soybean were investigated under the influence of biochar application in soils through pot experiments. A reduced BA content was observed in the soils after biochar application, and sorption and degradation of BA by biochar could not explain this change. BA contents inside and outside the soybean root also decreased after the addition of biochar, indicating a significant reduction in BA formation by the plant. The reduced lipid peroxidation (malondialdehyde (MDA) concentration) in soybean roots and promoted plant growth indicated that biochar application greatly reduced plant BA stress. Therefore, biochar addition into the soil can reduce the generation and release of BA from soybean root, which has a positive effect on alleviating allelopathy. This study provides a new angle for a comprehensive evaluation of the environmental impact of biochar and technical support for overcoming the obstacles in continuous cropping.

Micronutrient availability is low in Oxisols. Additionally, organic compounds in organomineral fertilizers (OMFs) used as a source of nitrogen (N), phosphorus (P), and potassium (K) may interact with metallic micronutrients in the soil, altering their dynamics and availability to crops. Therefore, the aim of this study was to assess the effects of NPK-OMFs, produced by composting mixtures of organic residues (chicken manure and coffee husk) and monoammonium phosphate (MAP), on the dynamics of iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) in the soil. The study also aimed to examine the availability and uptake of these micronutrients by maize cultivated in Oxisols. NPK-OMFs were produced using various proportions of organic residues and MAP. The availability of Fe, Mn, Cu, and Zn from OMFs was determined in both whole soil and solution during maize cultivation under greenhouse conditions in Red and Yellow Oxisols, which had contrasting soil organic matter (SOM) contents. Additionally, the release rate of micronutrients was evaluated in incubated soil-OMF mixtures. Higher proportions of organic residues in OMFs decreased the Mn content in the soil solution of Oxisols. It increased Fe and Cu levels in the Oxisol with higher SOM, but reduced Fe levels in the Oxisol with the lowest SOM level. In all Oxisols, OMFs with higher organic residues enhanced the availability of Zn. In the SOM-poor Oxisol, biomass, Fe, and Mn increased in the maize shoot. The use of NPK-OMFs alters the dynamics and improves the use efficiency, significantly affecting the availability of Mn, Zn, and Fe in the soil solution and, to a lesser extent, in the whole Oxisols compared to mineral fertilizers.

Polymer coating of water soluble fertilizers to curb excess solubilization of nutrients is well-acknowledged fact. Lack of information on phosphorus (P) release from controlled release nitrogen-phosphorus (NP) formulation and its impact on nutrient use indices has driven us to conduct this experiment. We developed NP formulations by reacting liquid ammonia and orthophosphoric acid in laboratory. Resulting NP formulations were characterized by solubility fractions, microscopy, spectroscopy, and X-ray diffraction. After coating with poly(vinyl alcohol) (PVA) and liquid paraffin (LP) at 2 and 3 w/w% concentration, P release kinetics and temperature sensitivity (Q10) of the formulations were compared with diammonium phosphate (DAP) at 20 and 30 °C temperature in a P-deficient soil for 120 h of incubation. Finally, nutrient use efficiency and relative efficiency indices were determined from a greenhouse experiment in potted soil to assess the effect of polymer-coated formulations and of DAP at two application rates in comparison with a non-P amended control. Laboratory synthesized NP formulations were alkaline in reaction, definite cubical to hexagonal crystalline structure with smooth surface generating peaks related to P and N in fingerprinting region of Fourier transform infrared spectroscopy. Polymer coating of NP formulations delayed the P release compared with DAP, while LP-coated formulations showing slower P release than PVA-based coatings. Despite LP-coated formulations showed greater temperature sensitivity (Q10), the PVA-based formulation significantly increased yield and biomass accumulation of wheat, with concomitant increase in crop P uptake and P use efficiency. Both LP and PVA-coated formulations showed a significant residual P accumulation in post-harvest soils. The findings underline the potential of polymer coating technology for enhancing P use efficiencies, thereby reducing environmental P footprints.