THE INVESTIGATION OF CROP WEEDINESS IN THE CROP ROTATION OF ORGANIC FARMING SYSTEM

Field experiments were conducted during the period of 2004 – 2006 at the Research and Study Farm „Vecauce”. The aim of the investigation was to establish the weediness’ dynamics of crops in a six-field crop rotation of an organic farming system. The field was certified as being organic. Crop rotation: 1. triticale/ rye (for green manure in spring), 2. oil radish (for green manure)/ rye (for green manure in autumn), 3. potatoes, 4. oats, 5. vetch-oats mix (for green forage) with an undersown mixture of red clover and timothy, 6. red clover and timothy. Conventional soil tillage was done according to the requirements of the crops. The weeds were counted two times during the vegetation period of crops: at the early development stages of crops (for instance, at the tillering of cereals) and before the crop harvesting. The composition of weed flora comprised from 59 species in the crops’ stands. The annual dicotyledonus were dominating groups of the weed flora. The most abundant weeds were lambsquarters (Chenopodium album L.), quackgrass (Elytrigia repens (L.) Nevski), common yellow rocket (Barbarea vulgaris R. Br.p.p.). The significantly smaller amount of weeds among crop rotation links was observed in the link rye/ oil radish/ rye – potatoes – oats. Much worse suppression of weeds was obtained in the crop rotation link red clover and timothy – triticale/ rye – oil radish/ rye. The number of weeds in the fields of crop rotation in the organic farming system is dependent on the cultivated crops, the succession of crops in the crop rotation links and crop cultivation technologies

The Effect of Cutting Regime and Cultivar on Longevity of Pure Lucerne Stands in Latvia

Lucerne growing is important for high and excellent quality yields of hay or silage without application of N fertilisers, as well as for increasing crop diversity in crop rotation systems. It is comparatively expensive to establish lucerne stands in Latvia. Different aspects can affect longevity of lucerne stands: suitability of cultivar to specific conditions, soil characteristics, different stress conditions and cutting management, including frequency and height of cutting, and critical rest period in autumn (Sheaffer et al., 1988). The aim of our study was to evaluate the persistence of lucerne stands without renovation while obtaining reasonable yields

Assessment of potato plant development from Minitubers

ArticleIn production of minitubers, mani pulation of their weight by modifying production method is common. Under field conditions plant development from minitubers can be affected by their weight, as well as cultivar. This objective of this study was to compare plant development from four minitu ber weight classes (MtC) (3 to 4.99 g, 5 to 9.99 g, 10 to 19.99 g, and > 20 g) with broken apical dominance of cultivars ‘Monta’, ‘Prelma’ and ‘Mandaga’. ‘Prelma’ and ‘Mandaga’ had a similar development pattern, and minitubers > 20 g required significantly less growing degree days (GDD) to emerge than minitubers from the lightest classes. The heaviest minitubers needed on average 176 GDD for 50% emergence and 207 GDD were needed for the lightest class. The difference in GDD between the marginal MtC was more pronounced in period between 50 and 80% emergence. MtC did not affect the final rate of emergence. Number of above ground stems (1.4 – 4.0) was significantly affected by MtC. ‘Monta’ had significantly different development – delayed emergence, lower emergen ce rate, less above ground stems, faster canopy closure. Our study showed that plant development was significantly affected by MtC and cultivar. Differences between MtC were more pronounced under adverse meteorological condi tions

Effect of nitrogen rate and forecrop on nitrogen use efficiency in winter wheat (Triticum aestivum)

ArticleApplication of plant nutrient is one of the most important measures increasing grain yield and yield quality. Excessive application of nitrogen fertilizers leads to nitrogen leaching and it affects the quality of groundwater and surface water. The objective of this research was to evaluate the effect of nitrogen fertilizer rate on nitrogen use efficiency in winter wheat after two forecrops. The experiment was conducted at the Research and Study farm ‘Pēterlauki’ of Latvia University of Life Sciences and Technologies (56° 30.658’ N and 23° 41.580’ E) in four growing seasons: 2014/2015, 2015/2016, 2016/2017 and 2017/2018. Researched factors were crop rotation (wheat/wheat and oilseed rape (Brassica napus ssp. oleifera/wheat) and five nitrogen fertilizer rates (kg ha-1 ): N0 or control, N60, N120(90+30), N180(90+60+30) and N240(120+60+60). Nitrogen fertilizer affected winter wheat grain yield significantly (P < 0.001) and average grain yield increased significantly (P < 0.049) until nitrogen rate N180. But analyzing it after each forecrop separately, yield increased significantly (P < 0.05) until N120 after both forecrops. Nitrogen fertilizer affected nitrogen use efficiency (NUE), nitrogen uptake efficiency (NUpE), nitrogen utilization efficiency (NUtE) and protein content significantly (P < 0.001). When increasing nitrogen fertilizer rate NUE, NUpE and NUtE decreased, and higher results were observed at the lowest nitrogen rates. Increased nitrogen fertilizer rate also increased crude protein content in grain, and for bread baking suitable grain was obtained only with the highest N rate: N 240. Forecrop did not affect winter wheat grain yield, however, it affected NUtE (P < 0.01), NUE (P < 0.001) and nitrogen harvesting index (P < 0.001) significantly; higher results were observed when wheat was grown after wheat

The effect of Minituber Weight on their Field Performance under a Northern European environment

ArticleWeight of potato minitubers as well cultivar affects field performance of minitubers. The aim of this study was to compare minitubers of four weight classes (MtC) (3 to 4.99 g, 5 to 9.99 g, 10 to 19.99 g, and > 20 g) with respect to their field performance. Three year experiments were conducted at AREI, Latvia (57°19′ N, 25°20′ E) between 2014 and 2016. Cultivars ‘Monta’, ‘Prelma’ and ‘Mandaga’ were used. A significant relationship between the number of stems and the number of progeny tubers per plant was detected and the number of stems explained 74% of variation in progeny tuber number. Multiplication rate, expressed as the number of progeny tubers > 25 mm per planted minituber, was in range from 4.2 to 13.1 tubers and was significantly affected by the cultivar and MtC. Cultivar and MtC had significant effect on the number of tubers and tuber yield per m2 . The number of progeny tubers and yield increased with increases for MtC. The highest number of progeny tubers (size > 25 mm) per m2 were obtained from minitubers > 20 g of ‘Prelma’ (93.4), but the highest yield was from minitubers > 20 g of ‘Mandaga’ (4.92 kg m-2 ). The effect of MtC was more pronounced on number of tubers than on tuber yield. Cultivar and MtC determined mean size (diameter (μ)) of progeny tubers. Mean size increased as MtC decreased. MtC had a significant effect on standard deviation (σ) only for ‘Prelma’. When σ was recalculated to coefficient of variation (CV), no significant effect of MtC remained

Role of humic substances in agriculture and variability of their content in freshwater lake sapropel

ArticleThe term ‘humic substances’ (HS) refers to a general category of naturally occurring, biogenic, heterogeneous organic substances. They create the most widespread natural organic matter found in sediments, soils and waters. Organic carbon in soil (up to 70%) and peat (up to 90%) usually occurs in the form of HS. HS influence the formation process of fossil fuels, as well as they are involved in the plant nutrition process, have an influence on availability and toxicity of metallic and other elements. Furthermore, HS play a significant role in the global carbon geochemical cycle. Properties and application efficiency of humus depend on the source of HS. Freshwater sapropel is a huge reservoir of HS with superior biological activity, although their total content is lower than in peat. The aim of this paper, firstly, was to present the information about the options of HS in agriculture and their main effects on plant growth. Secondly, determination and characterization of HS content in freshwater lake sapropel was performed as sapropel nowadays becomes a popular natural organic-mineral fertilizer and soil conditioner. Sapropel samples were derived from Lake Pilvelis, Lake Pilcines, Lake Vevers, Lake Liducis and Lake Padelis situated in Eastern Latvia. Investigation of HS content in sapropel is significant for the Baltic States and Northern Europe due to wide distribution and availability of sapropel in freshwater bodies. That promotes a search for new ways of extraction methods and bioeconomically effective utilization of this natural resource, obtainable in economically significant amounts, with high opportunities of its use especially in agriculture. Contemporary agriculture strongly desiderates in new products of high effectivity enhancing soil and crop productivity and quality hand in hand with sustainable development and careful attitude to the nature and surrounding environment, thus, one of the ways how it can be achieved is understanding how, where and how much HS preparations can be applied

Sowing time effect on yield and quality of field beans in a changing meteorological situation in the Baltic region

Received: January 26th, 2021 ; Accepted: June 26th, 2021 ; Published: June 30th, 2021 ; Correspondence: [email protected] field beans (Vicia faba L.) need a lot of moisture to germinate, growers believe that they should be sown as early as possible in the spring. Field trial was carried out at the LLU RSF “Pēterlauki”, from 2018 to 2020. Following factors were researched: A) sowing time (early, medium and late), B) variety (‘Laura’, ‘Boxer’, ‘Isabell’), C) sowing rate (30, 40, 50 germinable seeds m-2 ), D) fungicide application (without and with application of fungicide at the GS 61-65). Meteorological conditions during the study had the greatest impact on the results as they were contrasting. Adverse meteorological conditions for field bean growing were observed in 2018 and in spring and early summer of 2019. The best year for bean yield formation was 2020, when temperature and precipitation was moderate. The highest average three year been yield was obtained sowing beans at the medium sowing time, however, equivalent yield was obtained sowing beans also in early sowing time. Fungicide application increased average three year yield significantly (p = 0.007) and independently of the sowing time. Influence of variety and sowing rate on average three year yield was insignificant, and it was not proved that any variety or sowing rate could be more suitable in a specific sowing time. Average three-year values of crude protein content, thousand seed weight and volume weight were affected by sowing time significantly (p < 0.001). Trial year, variety and fungicide application also affected all quality parameters significantly (p 0.05)

Field bean (Vicia faba L.) yield and quality depending on some agrotechnical aspects

ArticleDespite growing interest about field beans ( Vicia faba L.), only few researches have been carried out in Baltic countries on the possibility to increase field be ans’ yield and quality depending on different agrotechnical measures. Field trial was carried out in 2015, 2016 and 2017. Researched factors during all years were: A – variety (’Laura’, ’Boxer’, ’Isabell’), B – seeding rate (30, 40 and 50 germinate able se eds m - 2 ), C – treatment with fungicide (with and without application of fungicide). Beans’ yield (t ha - 1 ) and yield quality characteristics were detected in the trial. Temperature and moisture conditions were mostly suitable for high yield formation of fie ld beans in all three trial years. In all three trial years, field bean yield has been significantly affected by all factors. The highest yield ( p = 0.001) was provided by variety ‘Boxer’ in all years (6.10 – 7.74 t ha - 1 ). Thousand seed weight (TSW) was sign ificantly affected by variety and fungicide application. From agronomical point of view, crude protein level was not importantly affected by seeding rate changes or fungicide application. Volume weight was affected significantly by increased seeding rate o nly in 2016. Fungicide application also did not affect volume weight significantly during the whole trial period. Field bean yield increased by each year, but the main tendencies in all years were the same: higher yield and TSW was provided by variety ‘Box er’, but higher protein content and volume weight – by ‘Isabell’. Seeding rate increase gave positive impact on yield. Fungicide application affected field bean yield, but did not affect its quality significantly

Variety, seeding rate and disease control affect faba bean yield components

ArticleFaba beans (Vicia faba L.) have been grown since 8000 years B.C. in the Middle East. Despite their long growing history in the world, there are only few researches carried out in Baltic region in last decades about variety, seeding rate and disease control effect on faba beans’ growth, development and yield formation. Research was carried out at the Latvia University of Life Sciences and Technologies during 2015–2017. Three factors were researched: A – variety (‘Laura’, ‘Boxer’, ‘Isabell’), B – seeding rate (30, 40 and 50 germinate able seeds m-2 ), C – treatment with fungicide (with and without application of fungicide Signum (1 kg ha-1 )). Meteorological conditions were diverse and sometimes caused stress for crop, but in general they favoured faba beans’ growth and development. High average yield of the field beans was obtained during all three trial years, however, yield differed significantly among them. Sowing time was constantly quite early, germination took longer time as expected due to the low air temperature, but later, temperature and humidity level improved and conditions were suitable for plant growth and development with some exceptions during flowering and pod filling. Number of productive stems per 1 m2 was significantly affected only by seeding rate. Plant height in trial site was affected by variety (p < 0.001), fungicide application (p = 0.008) and meteorological conditions (p < 0.001) of the year. Number of pods per plant differed depending on trial year (p < 0.001). Number of seeds per plant had a close positive correlation with number of pods per plant. Whereas number of seeds per pod was a relatively stable and typical characteristic for variety. We can observe correlation between faba bean yield and number of productive stems per 1 m2 at harvest, plant height, number of pods and seeds per plant