Wood ash as a vegetative-growth promoter in soils with subsurface compaction

ABSTRACT Subsurface soil compaction and nutritional stress are among the main factors that limit the yield of crops. Using forest residues, such as wood ash, is a viable option in the chemical recovery of soils and can promote vigorous root development in soils with subsurface compaction. The objective of this study was to indicate the most adequate dose of wood ash for efficient management of this residue applied in rotational crops cultivated in soils with subsurface compaction. Safflower plants (Carthamus tinctorius), a rotational crop with a deep taproot system, were grown in clay soil fertilized with different doses of ash and with induced levels of compaction in the subsurface layer. The experiment was conducted in a randomized block design, under a 4 × 5 factorial scheme, composed of four doses of wood ash (8.0, 16.0, 24.0, and 32.0 g dm-3) and five levels of soil bulk density (1.0, 1.2, 1.4, 1.6, and 1.8 kg dm-3), with four replicates. Crop growth variables (plant height, number of leaves, stem diameter, and SPAD chlorophyll index) were evaluated at 15, 45, and 75 days after emergence. The results indicated that soil compaction was the most limiting factor to the vegetative development of safflower, regardless of the ash dose. The interaction between the wood ash dose and bulk density, when present, showed that the best growth response occurred for ash dose of 25 g dm-3 for a soil bulk density of 1.2 kg dm-3.

Assessment of Soil Physical Quality and Water Flow Regulation under Straw Removal Management in Sugarcane Production Fields

Removing sugarcane straw to increase bioenergy production can generate significant income to the industry. However, straw contributes to the regulation of soil functions and consequently supports the provision of ecosystem services, such as water flow regulation. Thus, straw removal may hinder the provision of these services, especially in mechanized sugarcane production systems, which have soil compaction problems due to machinery traffic. In this study, we assess a six-year experiment in Brazil with four rates of straw removal: 0 Mg ha−1 (TR), 5 Mg ha−1 (HR), 10 Mg ha−1 (LR), and 15 Mg ha−1 (NR) remaining straw. Using attributes, such as soil bulk density, porosity, water infiltration, runoff, saturated hydraulic conductivity and available water-holding capacity, as indicators of key soil functions, we calculated a soil-related ecosystem service (ES) index for water flow regulation provision. The ES index revealed that water flow regulation was low regardless of the straw management (0.56, 0.63, 0.64 and 0.60 for TR, HR, LR and NR, respectively). It can be a consequence of soil compaction caused by machinery traffic throughout the successive cycle, whose straw was unable to mitigate this issue. Thus, by the end of the sugarcane cycle (sixth ratoon), straw removal had little effect on soil physical and hydraulic indicators, and consequently had little impact on the provision of the soil-related ES associated with water flow regulation. Nevertheless, straw management should be planned to consider other functions and soil-related ES benefited by straw retention.

Phenotypic response to soil compaction varies among genotypes and correlates with plant size in sorghum

Aims Soil compaction is a major yield-reducing factor worldwide and imposes physico-chemical constraints to plant growth and development. Facing limitations, roots can adapt and compensate for loss of functioning through their plasticity. Being primarily a belowground challenge, tolerance to soil compaction needs to be associated with root phenotype and plasticity. It is therefore of importance to distinguish between size-related apparent and size-independent adaptive plasticity. We determined the above- and belowground plasticity of sorghum genotypes varying in overall plant size. Methods We quantified plasticity as the degree response (adaptive and apparent plasticity) to soil compaction and conducted two experiments with sorghum and two soil density levels (1.4 and 1.8 Mg m−3). First, we quantified the shoot biomass plasticity of 28 sorghum genotypes. Second, we studied the root plasticity of six genotypes varying in shoot size and tolerance to soil compaction. Results Plasticity was correlated with plant biomass with larger genotypes responding earlier and more intensely. Soil compaction affected roots more than shoots and plasticity was expressed foremost in nodal root number and fine root length. Impeded plants produced 35 and 47% less root mass and length, respectively. Conclusions Plasticity to soil compaction varies among genotypes, but less-sensitive lines are in general smaller-sized genotypes. The association between tolerance and plant biomass may pose challenges to crop production; however, vigorous genotypes with unresponsive shoots to soil compaction do exist. Maintaining shoot growth relatively stable while the root modifies its structure can be an important adaptation mechanism to soil compaction.

THE INFLUENCE OF DIFFERENT CROP ROTATIONS AND FERTILIZATION SYSTEMS ON CHERNOZEM SOIL BULK DENSITY

The soil health can be deduced by chemical, biological and physical properties. This triad of features influence each other and equally determines soil quality and fertility. The paper includes the study regarding physical state of the chernozem soil characterized by bulk density – soil physical property that estimate soil compaction. The study took place in long-term field experiments of the Selectia Research Institute of Field Crop located in the North part of Moldova. The experimental data were obtained in 2019-2020 agriculture year. The soil bulk density, studied in different crop rotations and fertilization systems, was determined under winter wheat agrocenosis after harvesting in the 0-40 cm soil layer. The researches has shown that chernozem soil bulk density registered more favorable indices in crop rotations that include: perennial legumes and grasses in a mixture or only perennial legumes; less row crops - which means minimizing tillage (mechanic disturbance of soil). Regarding fertilization systems – the soil compaction is lower on the plots with adequate amount of organic fertilizer.

Method for Determining the Pressure of a Pneumatic Wheel on the Soil

A method for determining the pressure of a pneumatic wheel on the soil is proposed. The method consists in measuring the magnitude of the vertical acceleration of the axles of a self-propelled vehicle, its speed and air pressure in the tire. The research results allow the developers of vehicles fitted with pneumatic wheels to choose rational characteristics of tires and optimal parameters of the oscillatory system of wheeled tractors, which help to reduce soil compaction.

Characterization of the soil compaction based on the mapping of the apparent electrical conductivity

Based on the measurement of soil penetration resistance (PR), it is possible to identify compacted soil layers, where root growth may be harmed, affecting crop development and yield. The objective of this work was to analyze the use of management zones (MZ), delimited on the basis of mapping of the spatial variability of the soil apparent electrical conductivity (ECa), in the differentiation of soil compaction levels. The work was carried out in a 25.8-ha no-tillage area, cultivated under a center pivot. The ECa was measured under two soil moisture conditions (13.7 and 16.45%), using the Terram® equipment. Soil penetration resistance (PR) was measured using the SoloStar PLG5500 penetrograph. Based on the spatial variability ECa mapping, management zones (2, 3, and 4 zones) were delimited. The mean PR values ??of each MZ were compared by the t-test of means. It was possible to differentiate mean values ??of penetration resistance (PR), which vary from 0.9 to 2.10 MPa, from the characterization of management classes generated on the basis of the ECa spatial variability. The highest stratification of PR values ??was obtained as a function of sampling directed at delimited management zones when the soil had lower moisture content (13.7%). The highest mean PR values ??were obtained for the split of the ECa map into at least three classes. It was identified that for the study area there is no need to perform any mechanical decompaction operation.