Rapid Response Indicators for Predicting Changes in Soil Properties Due to Solarization or Biosolarization on an Intensive Horticultural Crop in Semiarid Regions

Agriculture practices developed since the middle of the last century have led to the degradation of different resources and made it necessary to promote agricultural models that are less aggressive towards nature. Sustainable agricultural growth requires a more efficient use of land. An experimental model was designed with four treatments in the Campo de Cartagena area (SE Spain): biosolarization with manure (BSM), biosolarization with brassicas (BB), solarization (S), and a pilot test (PT). The general objective was to determine by means of rapid response indicators the changes occurring in soil properties as a consequence of the implementation of these solarization or biosolarization practices and their influence on the quality and yield of a lettuce crop. The results show that there was no significant response in the physical and biological properties of the soil. Physicochemical properties such as pHw, and electrical conductivity (ECe), as well as chemicals such as total nitrogen (TN) and the content of some macro and micronutrients, can be considered as rapid response indicators. The highest yields (Yc) and highest commercial quality (Mc) of lettuce were obtained in the BB and BSM treatments (Yc > 23,000 kg ha−1; Mc > 413 g). These treatments resulted in biological NO3− sequestration and, in the case of BB, salt immobilization (ECe: 6 dS m−1). According to these results, BSM and BB can be recommended for sustainable agriculture and even as valid methods for the recovery of soils affected by salts and NO3−. Our results should increase the feasibility of these techniques in semiarid areas.

Comparative Study of Soil Properties under Gamhar (Gmelina arborea) Based Agrisilvicultural System

A two year experiment was conducted during kharif and rabi season of 2016-2017 and 2017-2018 at experimental site near Faculty of Forestry in main campus of Birsa Agricultural University, Ranchi, Jharkhand, India. Sole cropping and gamhar based agrisilviculture systems with four different intercrops (arhar, cowpea, greengram and mustard) were under investigation. To study the overall scenario of soil properties under agrisilviculture system, soil samples were analysed at different profile depths (0-15 and 15-30 cm) to measure the changes in soil properties under the influence of gamhar (Gmelina arborea) tree and intercrops grown in between. Soil pH, electrical conductivity (dsm-1), organic carbon (%), available nitrogen, phosphorus and potassium (kg ha-1) were found higher at the soil depth 0-15 cm as compared to 15-30 cm due to addition of organic residue on the surface soil. Soil OC, available N, P and K in 0-15 cm as well as in 15-30 cm profile was found to be statistically significant. It showed an increase from initial value in all the treatments in 2016-17 and 2017-18. The increase was more in gamhar based agrisilviculture system than in sole tree and sole crops in both the years.

Response of Annual Herbaceous Plant Leaching and Decomposition to Periodic Submergence in Mega-Reservoirs: Changes in Litter Nutrients and Soil Properties for Restoration

Litter decomposition is an important soil nutrient source that promotes vegetation in deteriorated riparian zones worldwide. The periodic submergence and sediment burial effects on two prominent annual herbaceous plants (Echinochloa crusgali and Bidens tripartite) are little known in mega-reservoir settings. Our study focuses on the mass and carbon loss and nutrient release from E. crusgali and B. tripartitle litter and changes in soil properties, which are important for riparian zone rehabilitation in the Three Gorges Dam Reservoir, China. This study adopted the litter bag method to explore the nutrient change characteristics and changes in soil properties at different sediment burial depths under flooding scenarios. Three burial depths (0 cm, 5 cm, and 10 cm) were used for these two plants, and the experiment lasted for 180 days. The results revealed that the litter decay rate was high at first in the incubation experiment, and the nutrient loss rate followed the pattern of K > P > N > C. The relationship between % C remaining and % mass remaining was nearly 1:1, and the total amount of P exhibited a leaching–enrichment–release state in the decomposition process. Nutrients were changed significantly in the soil and overlying water at the first decomposition stage. Still, the total soil nutrient change was insignificant at the end, except for the 10 cm burial of B. tripartitle. Moreover, oxidation–reduction potential was the main factor in the litter decomposition process at different burial depths. This study indicated that sediment deposition reduced litter mass loss, slowed down the release of N and P, and retained more C, but promoted the release of K. Conclusively, in litter decomposition under waterlogging, the total soil nutrient content changed little. However, litter does more to the soil than that. Therefore, it is necessary to study the residual soil litter’s continuous output after the water level declines for restoration purposes.

Combined Application of Rice Husk Biochar and Lime Increases Phosphorus Availability and Maize Yield in an Acidic Soil

Biochar, a pyrogenic carbon, has been receiving incremental attention for potential contribution to soil health, agricultural productivity enhancement while mitigating climate change by sequestering carbon and reducing greenhouse gas (GHG) emissions. However, it is not well-known to us how far rice husk biochar (RHB) application rates could increase phosphorus (P) bioavailability and plant performance when co-applied with P and lime. Here, we present data of a pot experiment consisting of eleven treatments to evaluate RHB, lime, and phosphorus effect on soil phosphorus availability, CO2 emission, nutrient uptake, and yield performance of maize. Co-application of RHB (10 and 15 t ha−1) and lime (100% and 75%) was made with different rates of P (100%, 75%, and 50%). Our result revealed that, at harvest, the combined application of RHB, lime, and phosphorus fertilizer significantly increased soil pH, P availability and decreased Al and Fe toxicity relative to the control while increasing maize yield. The maximum soil pH increased by 36.75%, the highest available P increased by 158.75%, whilst, the exchangeable Al content reduced by 96.84% compared to the control treatment. However, the difference in biomass production and yield among different lime, RHB, and P were minimal, with the largest grain yield (15.50 t ha−1) was recorded in the T6 treatments (75% lime + 10 t ha−1 RHB + 100% Triple superphosphate). The increment in biomass and grain yield could have occurred due to lime and RHB mediated changes in soil properties, including enhancement of soil pH, availability of P, and other nutrients. This increased availability then increased nutrient uptake and biomass production. Our results suggest that the combined application of lime and RHB could bring favorable changes in soil properties while sacrificing some carbon from soils.

Effect of Soil Degradation and Remediation in Technogenic Barrens on the Uptake of Nutrients and Heavy Metals by Plants in the Kola Subarctic

To assess the state of plants and their response to changes in soil properties, the elemental composition of leaves of widespread and pollution-tolerant species Betula pubescens Ehrh. and Salix caprea L. has been studied near the nonferrous metallurgy enterprises in the Kola Peninsula. The content of nutrients and heavy metals in the leaves of undergrowth on technogenic barrens and remediation sites differing in remediation technologies has been analyzed. According to the results of leaf diagnostics, both species under barren conditions are characterized by a noticeable deficiency of K, Ca, P, and, especially, Mn and Zn. The leaves of both species accumulate Ni, Cu, Co, As, Cr, Fe, Al, Pb, V, and S. Willow leaves contain more Cd, Co, Cr, Ni, Cu, Al, Fe, As, S, Ca, K and less Mn than birch leaves. Chemophytostabilization has little effect, and the covering of contaminated soils with a constructed fertile layer leads to the enrichment of birch and willow leaves with Ca, K, and P. Under conditions of continuing atmospheric emissions and gradual accumulation of bioavailable heavy metals in soils after the remediation, the accumulation of metals in leaves is largely determined by the distance from the pollution source, reflecting the possibility of both root and foliar uptake. The concentrations of Ni and Cu in leaves in 2018 did not decrease compared to 2011. The low, albeit varying, ratios of the contents of heavy metals in undergrowth leaves and in the soil and weak correlation of heavy metal contents in these media indicated that B. pubescens and S. caprea retain their ability to regulate their chemical composition even under extreme conditions of technogenic barrens. At the same time, supporting the protective capabilities of plants via optimizing mineral nutrition and soil acidity in combination with a reduction in atmospheric pollution is a prerequisite for efficient remediation of technogenic territories in the Far North.