Journal of Soil Science and Plant Nutrition

We aimed to evaluate the changes in grassland soils resulting from forest tree planting using two soil quality indices—a soil evaluation factor (SEF) and a soil quality index (SQI). We studied the impact of introducing forest trees (conifers, broadleaves or mixed) on natural meadows. We examined how the soil properties were affected by the tree species and their ages (25, 35 and 65 years old). Soil samples were collected from meadows and their adjacent forests, all situated within the boundaries of Krakow (Poland). Before the trees were planted, all areas were grassland, used for agricultural and recreational purposes. The soil samples taken from surface and subsurface horizons were analysed for pH, nutrients (C, N, P, K, Mg), humus compounds and dehydrogenase activity (DHA), and basic cations (Ca2+, Mg2+, K+, Na+). The introduction of trees on the grasslands lowered the pH and DHA activity, and impoverished the soils in nutrients. The impact on the soil properties of the tree species was more important than their age. The biggest negative changes were found in the soils covered by coniferous trees, in which the lowest values of SEF and SQI (respectively, 9 and 0.24) were recorded. The highest values of both soil quality indices (SEF—147, SQI—0.66) were observed in the meadow soils. The soils of a 35-year-old deciduous forest and a 65-year-old forest with deciduous and coniferous tree species had similar SEF and SQI values. The deciduous trees adapted better to the meadow soils than the conifers and, over time, an improvement in the soil properties occurred as a result of the accumulation of tree residues.

Calcareous soils usually exhibit low phosphorus availability. Low-molecular-weight organic acids are known to increase the release of phosphorus, but the release of phosphorus when low-molecular-weight organic acids, along with organic and inorganic amendments that coexist, is still poorly understood. The phosphorus release was studied with two soils: a clay loam and a sandy loam soil. These two soils were amended with three different organic and inorganic products at a rate of 5%, i.e., sugar beet bagasse ash, poultry manure, and sewage sludge. The phosphorus release was examined using a wide range (0, 0.1, 1, 2.5, 5, 10, 30, 50, 70, and 100 mM) of ubiquitous low-molecular-weight organic acids (citric, oxalic, and malic acids). The results showed that the ability of low-molecular-weight organic acids to release phosphorus followed the order citric > oxalic > malic. The release of phosphorus due to the application of low-molecular-weight organic acids from amended soils followed the order poultry manure > sewage sludge > sugar beet bagasse ash. The release of phosphorus from surface of calcium carbonate and, to a lesser extent, the surfaces of iron/aluminum oxides may be the primary cause of the release of phosphorus at low concentrations of low-molecular-weight organic acids, whereas calcium phosphate mineral dissolution is the primary cause of phosphorus release at high concentrations of low-molecular-weight organic acids. The PHREEQC program relatively well simulated the phosphorus release and equilibrium pH in different treatments. The release of phosphorus from low-molecular-weight organic acid–driven soil was influenced by the kind of low-molecular-weight organic acids, their concentrations, soil types, and the type of amendments.

Drought is the primary global limiting factor for agricultural production, and soybean plants are sensitive to water deficits. Management strategies have been studied to improve the yield in water-district areas. Applying biochar (BC) improves substrates’ physical and chemical properties, increasing water retention and nutrient availability. This study aimed to investigate whether the application of BC derived from acai (Euterpe oleracea) agroindustry waste could mitigate the deleterious effects of water deficit in soybean plants. The experiment was randomized using five proportions of BC [0.0, 2.5, 5.0, 7.5, and 10.0% (w/w)] obtained from the pyrolysis of E. oleracea seeds at 700 °C. In general, BC provided the best results at a concentration of 10% (w/w). BC positively modulated the stomatal mechanisms of plants subjected to water deficit, with increased stomatal density and functionality detected on both faces. This soil conditioner benefited physiological performance, promoting significant increases in the net photosynthetic rate (121%), water use efficiency (88%), and carboxylation instantaneous efficiency (180%), and minimizing the deleterious effects of water deficit on the gas exchange due to the benefits of stomatal regulation. The use of BC induced significant increases in biomass, including leaf dry matter (327%), root dry matter (40%), and total dry matter (84%). This study proved that BC plays an essential role in leaf water content, favors leaf development, and improves the performance of the photosynthetic machinery in soybean plants subjected to water deficit.

Vegetation restoration in disturbed areas can be achieved by passive (spontaneous succession, PR) and active (human-induced, AR) approaches. However, the contributions of different restoration strategies to the soil physicochemical properties and the bacterial community dynamics remain unclear in semiarid coal mining-disturbed areas. We compared the soil properties and bacterial communities in coal mining subsidence areas with AR and PR approaches after 0–15 years of restoration and evaluated the relationships among the vegetation, soil properties, and bacterial communities. Soil bulk density, moisture, organic carbon, available N/P/K, enzymes, and bacterial community diversities decreased in the initial revegetation stage (< 5 years) compared with those in nonsubsidence areas (NS) and then increased during succession at both the AR and PR sites. AR accelerated the recovery of the soil variables relative to passive restoration. The levels of the soil physicochemical properties at AR and PR sites did not recover to NS levels except for soil moisture. Furthermore, the abundance of the dominant bacterial groups did not exhibit good stability, but the bacterial community diversity was restored to the level before surface subsidence after 15 years of revegetation. Plant community biomass, soil bulk density, moisture, organic carbon, available N/P, and enzymes were the most important factors affecting soil microbial communities, while total N, available K, and soil pH showed the absence of a significant relationship. AR can speed up the recovery of the soil variables relative to passive restoration because artificial intervention is important for establishing sustainable soil ecosystems in semiarid disturbed areas.

A better understanding of crop and soil response to biosolids is necessary for optimizing their use as soil amendments. The present study examined the influence of sewage sludge application on N accumulation, partitioning, translocation, and N use in sunflower and on soil properties compared with mineral fertilizers. Treatments included the application of sewage sludge (9, 18, and 36 Mg dry weight ha−1 year−1), an inorganic fertilizer (138 kg N plus 55 kg P2O5 ha−1 year−1), and a non-amended control. Sewage sludge increased early crop growth rate and N uptake at levels similar to or even greater than those obtained with the inorganic fertilizer. Nitrogen translocation was correlated with nitrogen translocation efficiency (r = 0.66*); both parameters appeared to be associated with source and sink attributes. Nitrogen use efficiency and nitrogen uptake efficiency were decreased with increasing rates of sewage sludge following a quadratic response curve. The estimated nitrogen use efficiency of sewage sludge-added N was greater than that of the inorganic fertilizer when sewage sludge was applied at agronomically realistic rates (< 26 Mg ha−1 in the first year or < 18 Mg ha−1 in the second year). Sewage sludge application increased soil organic matter and Olsen P compared with the control. Soil electrical conductivity in sewage sludge treatments remained at acceptable levels and soil concentrations of DTPA-extractable trace elements were similar to those of the control or the inorganic fertilizer. In the light of these findings, treated municipal sewage sludge may be used in sunflower intended for biodiesel production replacing mineral fertilizers serving as alternative sewage sludge disposal method.

Soil aggregate stability is considered feasible and important indicator for understanding complex interactions between soils’ physico-chemical and biological properties and soil structure. The present study was therefore, conducted to find out the land-use change induced alteration in soil organic carbon (C) pool in response to changed restored engineering. The present study was conducted to reveal the distribution of water stable aggregates, aggregate stability, aggregate associated C of macro-and micro-aggregates, C preservation capacity of aggregate, and the labile and non-labile C fractions of variable oxidizability due to land-use change from the uncultivated soils to under rice-wheat, seed sugarcane, ratoon sugarcane and permanent grasslands in north-western India. These results showed that water stable aggregates, macro-and micro-aggregates, C preservation capacity, aggregate ratio and total organic carbon (TOC) stocks were significantly (p < 0.05) higher in permanent grassland and uncultivated soils. Ratoon sugarcane soils had ~ 10.3% higher TOC pool than the seed sugarcane. A significant decrease in TOC pool by ~ 11.3–11.9% occurred in soils under seed sugarcane cultivation, compared to others. Soils under seed sugarcane had ~ 11.5% lower C stocks, compared with the rice–wheat soils. As compared with the uncultivated soils, highest C loss of 3.3–3.7 Mg C ha−1 occurred in soils under seed sugarcane, followed by almost equal in rice-wheat (1.9–2.0 Mg C ha−1) and ratoon sugarcane (1.9–2.1 Mg C ha−1). The greatest C loss in soils under seed sugarcane was ascribed to increased tillage intensity. More intensified tillage under seed sugarcane cultivation resulted in decreased proportion of macro-aggregates (> 0.25 mm) and greater stabilization of organic C in relatively recalcitrant C pool as compared to those under ratoon sugarcane. Active C (Fract. 1 + Fract. 2) pool in surface soil layer under ratoon sugarcane was significantly higher by ~ 25.1–64.9%, compared with others. Conversely, the passive C pool (Fract. 3 + Fract. 4) was significantly lower in soils under seed sugarcane, while the highest in grassland. The proportion of macro-aggregates in soils under different land-use systems exhibited a linear significant relationship with the TOC pool (R2=0.964*; p < 0.05). Soils under seed sugarcane have significantly lower C preservation capacity of macro-aggregates by ~ 42.5%, compared with the ratoon sugarcane. Rice–wheat ecosystem had significantly higher C preservation capacity of macro-aggregates (> 0.25 mm) by ~ 0.70 g C kg−1 soil (~ 80.5%) than the seed sugarcane. The sensitivity index showed significantly higher sensitivity of TOC pool for soils under seed sugarcane (by ~ 8.6–21.8%), followed by ratoon sugarcane (~ 10.3–13.6%) and rice–wheat (~ 7.6–11.8%), while the lowest for grassland ecosystems (~ 0.2–0.5%) following the land-use change from uncultivated lands. Among the three cropland ecosystems, C preservation capacity of macro-aggregates was significantly higher than the sugarcane-based ecosystems. Considering uncultivated lands as reference, the soils under ratoon sugarcane had significantly higher C management index (CMI) than the other compared land-use systems. The highest values of the CMI in soils under ratoon sugarcane indicate C rehabilitation, while the lower values for seed sugarcane indicate C degradation. We put forward general management suggestions for different land-use and focus on better measures for the management of rice-wheat and seed sugarcane to reduce C losses by increasing aggregate stability of soils under different land-use systems.

Dark septate endophytes (DSEs) are a diverse group of fungi that form mutualistic relationships with plant roots, especially under stressful conditions such as heavy metal exposure, water limitation, and exposure to xenobiotics. DSEs belong to the phylum Ascomycota, and mainly colonize the parenchymal tissue of plant roots either intra- or intercellularly. These fungi synthesize dark pigments called melanins, which are considered to be important in their ability to tolerate extreme or toxic environmental conditions. The aim of this study was to gather information on the current state of knowledge regarding melanins from DSE fungi. While most DSEs synthesize 1,8-dihydroxynaphthalene (DHN)-melanin, some can also synthesize other types of melanin such as 3,4-dihydroxyphenylalanine (DOPA)-melanin, pyomelanin, and heterogeneous ones. Additionally, the genome of some DSEs contains genes that are involved in various melanin synthesis pathways. Understanding the diversity and characteristics of melanins from DSE fungi and their main melanization pathways could contribute to a better understanding of the role of melanins in these mutualistic fungi. The chemical nature and function of many of the dark pigments synthesized by these fungi are not yet known, so further research is needed to elucidate their contribution to stress tolerance and their impact on the interaction of DSE fungi with various plants of agro-forestry importance.

Soils are characterized by high phosphorus (P) immobilization, considering the major limiting factor for agricultural production in Brazil. Phosphate fertilizers complexed with humic acids (HA) have been presented as an alternative to inhibit P immobilization in soils; however, little is known regarding its efficiency or its effect on soil P dynamics when associated with liming. The objective was to investigate labile moderately and non-labile P changes in sandy and clayey soils under application of distinct P sources and liming. Tropical soils were incubated using 200 mg kg−1 of P (simple superphosphate—SSP and SSP + HA), associated or not with calcium oxide. Check-plots were run in both soils without any P addition and/or no liming. After 60, 90, and 180 days of incubation, P contents were fractionated into P inorganic (Pi) and organic (Po), in the following pools: labile (PAER and PBIC), moderately labile (PHCl and PHID-0.1), and non-labile fractions (PHID-0.5 and Presidual). There was a P flux between non-labile and labile fractions, controlled by the use of P fertilizer and liming. In sandy soil, the P addition promoted a clear P flux from non-labile to labile fractions; however, in clayey soil, there was a reverse P flux. The lack of P addition promotes a negative balance in soil with a decrease of labile fractions, mainly when associated with liming. Therefore, inputs are necessary to avoid soil P depletion.

The aim of this study is to investigate the effect of nitrogen (N) in the regulation of grain yield, growth, and physiology and biochemistry of fragrant rice under lead (Pb) stress. Three fragrant rice cultivars (Daohuaxiang, Basmati, and Yungengyou14) were grown under two N application levels (CK, 0 kg N ha−1, and HN, 200 kg N ha−1) under Pb-contaminated soil. The grain yield, growth, antioxidant attributes, and N metabolism of fragrant rice cultivars were investigated. Results showed that compared with CK, HN treatment increased grain yield in Daohuaxiang, Basmati, and Yungengyou14 by 24.09%, 26.74%, and 23.29%, respectively. Improvement in the effective panicle, grain number per panicle, and 1000-grain weight and agronomic traits under HN treatment was detected. HN treatment decreased the seed setting rate in the three fragrant rice cultivars. In addition, the peroxidase (POD), catalase (CAT), and glutamate synthetase (GOGAT) activity in HN treatment were increased for the three fragrant rice cultivars at both heading stage and maturity as compared to CK. The correlation between the grain yield and the other investigated parameters has also been accessed. Yungengyou14 produced the highest partial factor productivity of N and agronomic use efficiency of N. Those results suggested that N could improve the grain yield resulted from affecting the growth and physiological response of fragrant rice grown under Pb-contaminated soil.