Comparison of Compaction Alleviation Methods on Soil Health and Greenhouse Gas Emissions

Soil compaction can occur due to trafficking by heavy equipment and be exacerbated by unfavourable conditions such as wet weather. Compaction can restrict crop growth and increase waterlogging, which can increase the production of the greenhouse gas nitrous oxide. Cultivation can be used to alleviate compaction, but this can have negative impacts on earthworm abundance and increase the production of the greenhouse gas carbon dioxide. In this study, a field was purposefully compacted using trafficking, then in a replicated plot experiment, ploughing, low disturbance subsoiling and the application of a mycorrhizal inoculant were compared as methods of compaction alleviation, over two years of cropping. These methods were compared in terms of bulk density, penetration resistance, crop yield, greenhouse gas emissions and earthworm abundance. Ploughing alleviated topsoil compaction, as measured by bulk density and penetrometer resistance, and increased the crop biomass in one year of the study, although no yield differences were seen. Earthworm abundance was reduced in both years in the cultivated plots, and carbon dioxide flux increased significantly, although this was not significant in summer months. Outside of the summer months, nitrous oxide production increased in the non-cultivated treatments, which was attributed to increased denitrifying activity under compacted conditions.

Effects of Tractorization and Organic Manure on Physical Properties of Sandy Loam Soil in Abeokuta, Nigeria

Soil compaction has effect on soil physical properties which could affect crop growth and yield. This study was conducted to determine the influence of incorporating organic materials and load application (tractorization) on the physical properties of sandy loamy soil in Abeokuta, Ogun State, Nigeria. Organic materials were cow dung, poultry and swine manure. Application rates of organic manures were 0 (control), 5 and 10 tonnes per hectare. Forty-five plots measuring 5 by 3 m were established in a complete randomized block experimental design with three replications making a total of 135 plots. Load application was done using an MF 435 tractor coupled with a 20-disc harrow at 0 (control), 5, 10, 15 and 20 passes. Penetration resistance, bulk density, gravimetric moisture content andporosity were determined using standard procedures. Penetrometer resistance at these passes were 392.2, 293.3, 285.0, 302.0 and 224.9 kPa respectively with significant differences between treatments (P≤0.05). Mean bulk density for the passes were 1.21, 1.26, 1.31, 1.27 and 1.29 g/cm3 respectively and bulk density increased with tractor passes. The effect of tractor passes, and manure incorporation rate did not have any significant effect on gravimetric moisture content. Poultry manure increased bulk density and penetrometer resistance on plots than swine manure and cow dung hence poultry manure at 10 t/ha can be incorporated on a sandy loam soil to enhance soil fertility and sustainability. Keywords: Tractorization, organic manure, sandy loam, penetration resistance, bulk density

Root anatomical traits contribute to deeper rooting of maize under compacted field conditions

To better understand the role of root anatomy in regulating plant adaptation to soil mechanical impedance, 12 maize lines were evaluated in two soils with and without compaction treatments under field conditions. Penetrometer resistance was 1–2 MPa greater in the surface 30 cm of the compacted plots at a water content of 17–20% (v/v). Root thickening in response to compaction varied among genotypes and was negatively associated with rooting depth at one field site under non-compacted plots. Thickening was not associated with rooting depth on compacted plots. Genotypic variation in root anatomy was related to rooting depth. Deeper-rooting plants were associated with reduced cortical cell file number in combination with greater mid cortical cell area for node 3 roots. For node 4, roots with increased aerenchyma were deeper roots. A greater influence of anatomy on rooting depth was observed for the thinner root classes. We found no evidence that root thickening is related to deeper rooting in compacted soil; however, anatomical traits are important, especially for thinner root classes.

The Accessibility of Post-Fire Areas for Mechanized Thinning Operations

In 1992, in Southern Poland, large areas of Silesian forests were affected by the country’s largest forest fire. Stands introduced in the 9000-ha post-fire region are currently undergoing early thinning. Due to the scope of these treatments, the chance for their timely implementation is ensured only by the application of cut-to-length (CTL) technologies, i.e., with the use of harvesters and forwarders. The use of CTL technologies may, however, be difficult due to the fire history of these stands, which could affect the bearing capacity of their soils. The objective of this study is to determine the accessibility of stands for forest machines in relation to the bearing capacity of the soils and changes in soil compaction in the post-fire sites. Soil compaction was measured in terms of penetrometer resistance in the stands introduced in the post-fire area in question, as well as in control stands growing on five different soil types. It was shown that in the topsoil layer—from 8 to 18 cm thick depending on the soil type—differences in soil compaction in the post-fire and control areas were relatively small. The impacts of the forest fire—manifested as a significant increase in the compaction of the forest soils—were still visible, but only in the deeper layers of the soil profile. In all of the compared pairs of forest compartments located in the stands regenerated after the fire, significantly higher values of cone indexes (CI) were found. The average value of this index in the post-fire stands was 2.15 MPa, while in the control stands it was 1.60 MPa, which indicates that in both groups of stands the bearing capacity of the soils should not limit the accessibility for vehicles used for timber harvesting and extraction.

Genetic Architecture of Maize Rind Strength Revealed by the Analysis of Divergently Selected Populations

ABSTRACTStalk lodging, breakage of the stalk at or below the ear, causes substantial yield losses in maize. The strength of the stalk rind, commonly measured as rind penetrometer resistance (RPR), is an important contributor to stalk lodging resistance. To enhance RPR genetic architecture, we conducted selection mapping on populations developed by 15 cycles of divergent selection for high (C15-H) and low (C15-L) RPR. We also performed time-course transcriptome and metabolic analyses on developing stalks of high (Hrpr1) and low (Lrpr1) RPR inbred lines derived from the C15-H and C15-L populations, respectively. Divergent selection significantly altered allele frequencies at 3,656 and 3,412 single nucleotide polymorphisms (SNP) in the C15-H and C15-L populations, respectively. While the majority of the SNPs under selection were unique, 110 SNPs were common in both populations indicating the fixation of alleles with alternative effects. Remarkably, preferential selection on the genomic regions associated with lignin and polysaccharide biosynthesis genes was observed in C15-H and C15-L populations, respectively. This observation was supported by higher lignification and lower extractability of cell wall-bound sugars in Hrpr1 compared to Lrpr1. Tricin, a monolignol important for incorporation of lignin in grass cell walls, emerged as a key determinant of the different cell wall properties of Hrpr1 and Lrpr1. Integration of selection mapping with transcriptomics and previous genetic studies on RPR identified 40 novel candidate genes including ZmMYB31, ZmNAC25, ZmMADS1, two PAL paralogues, two lichenases, ZmEXPA2, ZmIAA41, and Caleosin. Enhanced mechanistic and genetic understanding of RPR provides a foundation for improved stalk lodging resistance.

Seeding densities of the oat crop and the amount of grazing on the physical property and soil carbon

The objective of this study was to evaluate the effect of two sowing densities of oat crop, managed in an integrated crop-livestock system (ICLS), or the use of fallow during the winter period, on the soil physical properties, total carbon and soil carbon stock, in two years. A split-plot in a randomized block design, with additional treatment was used. It was found that the number of grazing in the year 2014 adversely affected the values of macroporosity and microporosity in the layer 0-0.05 m, besides the microporosity in the 0.1-0.2 m layer. The total porosity in the 0.1-0.2 m layer was positively influenced by the sowing density of oats only in the year 2014. The soil penetrometer resistance (SPR) had changes after winter 2015, at 0-0.05 m due to the number of grazing. During 2014, there were no changes in the total carbon and carbon storage of the soil. In 2015, the amount of grazing used, negatively affected the total carbon in layers 0-0.05 and 0.1-0.2 m. However, it positively affected the storage of carbon in soil in the layer 0.05-0.1 m. The adoption of the lower density of the oat crop with realization of a grazing tends to improve the physical properties, total carbon and soil carbon stocks.