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  • Author: Solveiga Maļecka x
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Influence of waste liquors of mildronate production on yield and quality of winter rapeseed

The effect of mother liquors obtained in one production stage of the popular medicinal preparation Mildronate on yield and quality of winter rape (Brassica napus L.) grown for biofuel was tested. The mother liquors contain quaterine-type compounds, which are known to stimulate growth of lupines. In the three-year study, Mildronate mother liquors were sprayed on winter rape. The yield and fat content of rape was determined. Mother liquor contains small amounts of methyl acrylate. However, this compound was not found in rapeseed, stalks and soil. Mother liquors spray had a positive effect on soil microorganisms. In the period from initiation of flowering to maximum flowering stage, spraying with mother liquors, as well as with quaterine-M and isopropanol (basic substance of mother liquor), in most cases had a low (around 10%) positive effect on rape yield and a very small impact on the fat content in rape grain. The effects differed among years, suggesting interaction with weather conditions. The determined optimal mother liquors dosages were quite wide, from 0.4 to 10 L ha-1.

Abstract

Commercial products with humic substances have often been recommended for plant growth stimulation and yield improvement. The aim of this study was to clarify the effects of two products, containing cavited peat and vermicompost respectively on the soil biological activity. Vegetation experiments with garden cress and cucumbers were arranged in pots with a peat substratum in the greenhouses of the Latvia University of Agriculture. The plants were treated with the preparations once a month. The first treatment was done at sowing. Dose of 20, 2, 0.2 mL per m2 during each treatment time were used. A control variant was without peat or vermicompost preparation. Field experiments with onions were carried out in the organic farming experimental field of the Latvia State Institute of Cereal Breeding. Plant growth and soil (substratum) biological activity (respiration and enzymatic activity) were tested. Plant growth and response to the different preparations depended on the plant species and its development stage. The effect of preparations decreases during plant development. The impact of peat or vermicompost preparation on soil biological activity depended not only on the concentration of preparation, but was influenced by the soil or growth media type. The decrease of onion yield in field conditions as a result of preparations was observed.

Humic substances (HS) extracted from various organic materials have been shown to stimulate plant growth. However, scarce information is available on the impact of different methods of application of HS on nutrient status of vegetable species, especially in soil and climate conditions of the temperate zone. The goal of the present study was to evaluate the effect of pre-plant (bulblet soaking) and foliar application of commercially-produced peat and vermicompost-derived HS preparations on nutrient status and yield of onion (Allium cepa L.) in field experiments using two farming systems - conventional and organic. Although the effect was variable between nutrients, dependent on timing, application methods and farming systems, pre-plant and foliar HS tested was hardly effective in preventing nutrient (S, Zn, B) deficiencies limiting onion yield. Moreover, HS induced changes that significantly reduced nutrient status of organically grown onion and had detrimental effect on yield. Although one-year results did not suggest a benefit from HS application, further studies are necessary to evaluate the possible effectiveness of peat and vermicompost extracts on onion production in Latvia.

Diseases of rye (Secale cereale), an important crop in Latvia, might be a risk factor for rye production. The aim of the study was to determine features of rye leaf diseases, to estimate the risk of rye diseases under conditions of Latvia, and to compare various schemes of fungicide treatment that possibly might be useful for integrated disease control. Field trials were carried out from 2009 to 2012 in two locations in Latvia - State Stende Cereals Breeding Institute and State Priekuïi Plant Breeding Institute. Sixteen trials (two cultivars each year, two sites, and four years) were established during the investigations. Each trial was one-factor design with three variants of fungicide treatment: control (without fungicides), standard treatment during heading (GS 51-55), and DSS (Decision support system). Leaf scald caused by Rhynchosporium secalis and brown rust, caused by Puccinia recondita, were found to be the most important rye diseases during the study. Average additional yield achieved by fungicide application was 8%. Number of rainy days (more than seven, starting from GS 31) was not a sufficient threshold for the control of rye diseases. It was necessary to make assessment of the disease development in the the field. Fungicide application might be necessary if symptoms of leaf scald appear on the youngest leaves after beginning of stem elongation (GS 31-32).

Extracts for agricultural use were prepared using cavitation method at 45 oC and at 95 oC from peat and earthworm biohumus. Samples of all studied extracts had similar dry-matter content. Peat humic substances and earthworm biohumus extracts were analysed using UV-Vis, FT-IR, and fluorescence spectrometry. Trace element analysis was performed with atomic absorption spectrometry. Extracts were tested for acidity, conductivity, humic acid concentration, and carboxyl group concentration. Hydrophobicity was assessed using a water-polyethylene glycol twophase system and calculation of the partition coefficient. Total nitrogen and phosphorus concentration was determined. Concentration of the humic substances slightly changed during the heating process. Significant changes in total phosphorus concentration was observed both in earthworm humus and peat extract. Thermal treatment caused decrease of hydrophobicity and lower concentration of organic matter in extracts, while carboxyl group concentrations in isolated humic substances practically did not change. The calculated ratio from UV-Vis spectra showed significant difference in humification degree of samples.