Developing Functional Relationships between Soil Waterlogging and Corn Shoot and Root Growth and Development

Short- and long-term waterlogging conditions impact crop growth and development, preventing crops from reaching their true genetic potential. Two experiments were conducted using a pot-culture facility to better understand soil waterlogging impacts on corn growth and development. Two corn hybrids were grown in 2017 and 2018 under ambient sunlight and temperature conditions. Waterlogging durations of 0, 2, 4, 6, 8, 10, 12, and 14 days were imposed at the V2 growth stage. Morphological (growth and development) and pigment estimation data were collected 15 days after treatments were imposed, 23 days after sowing. As waterlogging was imposed, soil oxygen rapidly decreased until reaching zero in about 8–10 days; upon the termination of the treatments, the oxygen levels recovered to the level of the 0 days treatment within 2 days. Whole-plant dry weight declined as the waterlogging duration increased, and after 2 days of waterlogging, a 44% and 27% decline was observed in experiments 1 and 2, respectively. Leaf area and root volume showed an exponential decay similar to the leaf and root dry weight. Leaf number and plant height were the least sensitive measured parameters and decreased linearly in both experiments. Root forks were the most sensitive parameter after 14 days of waterlogging in both experiments, declining by 83% and 80% in experiments 1 and 2, respectively. The data from this study improve our understanding of how corn plants react to increasing durations of waterlogging. In addition, the functional relationships generated from this study could enhance current corn simulation models for field applications.

ANALYSIS OF HEATING PROCESSES OF URBANIZED TERRITORIES OF THE KHARKIV REGION AND MEASURES TO COMBAT THEM

Flooding of urbanized areas causes and activates dangerous geological pro-cesses, is a real threat to the safety of life of the population and the functioning of economic facilities. In this regard, the issues of studying the conditions for the devel-opment and spread of flooding on the territory of Ukraine are important and urgent. The article identifies the factors causing flooding of urbanized areas. The trends in the development of flooding in the Kharkiv region and the city of Kharkiv are deter-mined. In Ukraine, the flooded area is about 8 million hectares, and the number of flooded settlements is up to 5 thousand. The most flooded are Odessa, Nikolaev, Kherson regions. In the Kharkiv region, flooding is widespread in 39 cities and ur-ban-type settlements, and in 205 villages on an area of 200,8 km2, the affected area is 0,6 %. Flooding is observed in all districts of the region. The most flooded cities are Kharkiv, Barvenkovo, Valki, Izyum, Pervomaisky, the total flooded area was 185,7 km2, urban-type settlements Krasnopavlovka and Pechenegi, the total flooded area – 15,1 km2. The reasons for the flooding have been established. The consequences of flooding of urbanized territories are analyzed. Flooding leads to a deterioration in the condition of built-up areas and sanitary living conditions of people, an increase in morbidity, pollution of water and soil, waterlogging of significant areas of land, con-tributes to the development of negative physical and geological processes such as landslides, karst, etc., which can lead to subsidence of buildings and structures, and further to their destruction, deformations of underground engineering networks. Ana-lyzed measures to combat flooding, which can be divided into preventive and elimi-nation of already existing flooding. The activities that are proposed to be held in the city of Kharkov and the Kharkov region are outlined.

Identification of ABA-Mediated Genetic and Metabolic Responses to Soil Flooding in Tomato (Solanum lycopersicum L. Mill)

Soil flooding is a compound abiotic stress that alters soil properties and limits atmospheric gas diffusion (O2 and CO2) to the roots. The involvement of abscisic acid (ABA) in the regulation of soil flooding-specific genetic and metabolic responses has been scarcely studied despite its key importance as regulator in other abiotic stress conditions. To attain this objective, wild type and ABA-deficient tomatoes were subjected to short-term (24 h) soil waterlogging. After this period, gas exchange parameters were reduced in the wild type but not in ABA-deficient plants that always had higher E and gs. Transcript and metabolite alterations were more intense in waterlogged tissues, with genotype-specific variations. Waterlogging reduced the ABA levels in the roots while inducing PYR/PYL/RCAR ABA receptors and ABA-dependent transcription factor transcripts, of which induction was less pronounced in the ABA-deficient genotype. Ethylene/O2-dependent genetic responses (ERFVIIs, plant anoxia survival responses, and genes involved in the N-degron pathway) were induced in hypoxic tissues independently of the genotype. Interestingly, genes encoding a nitrate reductase and a phytoglobin involved in NO biosynthesis and scavenging and ERFVII stability were induced in waterlogged tissues, but to a lower extent in ABA-deficient tomato. At the metabolic level, flooding-induced accumulation of Ala was enhanced in ABA-deficient lines following a differential accumulation of Glu and Asp in both hypoxic and aerated tissues, supporting their involvement as sources of oxalacetate to feed the tricarboxylic acid cycle in waterlogged tissues and constituting a potential advantage upon long periods of soil waterlogging. The promoter analysis of upregulated genes indicated that the production of oxalacetate from Asp via Asp oxidase, energy processes such as acetyl-CoA, ATP, and starch biosynthesis, and the lignification process were likely subjected to ABA regulation. Taken together, these data indicate that ABA depletion in waterlogged tissues acts as a positive signal, inducing several specific genetic and metabolic responses to soil flooding.

The effect of soil water content and biochar on rice cultivation in polybag

Rice (Oryza sativa L.) production is important in the national food of Indonesia. The growth and yield of rice can be increased by the soil water supply and biochar application into the soil in a polybag. Water is a unique material resource that plays a vital role in agriculture. Biochar is a carbon-rich product obtained from biomass and can hold water and nutrients, making them more available to plants. The biochar used in this study was made from rice husks. This study aims to determine the effect of soil water content and biochar application in the soil on the growth and yield of rice in the polybag. The experiment appears to be a randomized multifactorial design with one factor being water content and the other being biochar application rate. A completely random design usually suggests only one factor in the experimental design. The first factor was soil water content consisting of two levels, i.e.: field capacity and soil waterlogging. The second factor was the biochar application consisting of four doses i.e.: 0; 14; 28; and 42 tons/ha. The results of the research showed that rice cultivation with soil water-logging is better than field capacity on the tillers number, panicle length, and harvest index. Without biochar application was given higher tillers number, but biochar dose of 14 tons/ha produced wider leaf area. There was a significant interaction between soil water content and biochar application on the dry weight of roots, shoots, and grains. The treatment combination of soil waterlogging and biochar dose of 14 tons/ha was most effective at increasing the growth and yield of rice in a polybag.

Adaptation to Early-Season Soil Waterlogging Using Different Nitrogen Fertilizer Practices and Corn Hybrids

Excessive rainfall occurring in the early spring season in the Midwestern United States result in waterlogged soils contributing to corn production losses. The objective of our study is to evaluate the impact of soil waterlogging [non-waterlogged or waterlogged for 7 days when corn was at V3 growth stage (corn plant having three fully developed leaves with collar visible)], different pre-plant nitrogen (N) fertilizer sources and post-waterlogging rescue N fertilizer on grain and silage yield of two commercially available corn hybrids with different flood tolerance. Pre-plant N fertilizer was applied at 168 kg N ha−1. Nitrogen sources were a non-treated control (CO), polymer coated urea (PCU), urea (NCU), and urea plus Instinct (NCU + NI). A post-waterlogging rescue N fertilizer was applied at V7 as 0 or 83 kg N ha−1 of urea plus N-(n-butyl) thiophosphoric triamide (NBPT) (NCU + UI). Waterlogging decreased grain and silage yields in different years; however, significant interactions were observed among treatments. Rescue N applications increased grain yields by 6–46% in non-waterlogged treatments, but not in waterlogged treatments. The PCU and NCU + NI increased grain yields compared to the CO. Pre-plant N sources showed no significant differences in grain yield, probably due to existing environmental conditions or incorporation of fertilizer. The N source, application method, and timing for post-waterlogging rescue N application and flood-tolerant corn hybrids needs further investigation in poorly-drained claypan soils prone to waterlogging under a changing climate.