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)

Winter wheat leaf blotches development depending on fungicide treatment and nitrogen level in two contrasting years

Received: January 31st, 2021 ; Accepted: December 1st, 2021 ; Published: December 4th, 2021 ; Correspondence: [email protected] spot (caused by Pyrenophora tritici-repentis) and Septoria tritici blotch (caused by Zymoseptoria tritici) are the most widespread winter wheat leaf diseases in Latvia. The aim of the present research was to clarify the development of leaf blotches on winter wheat depending on fungicide treatment schemes under four nitrogen rates. A two-factorial trial was conducted at the Research and Study farm “Pēterlauki” (Latvia) of Latvia University of Life Sciences and Technologies. For this study, data from the 2018/2019 and 2019/2020 growing seasons was used. Four schemes of fungicide application and an untreated variant, as well as four nitrogen rates (N120, N150, N180, and N210 kg ha-1 ) were used. The total disease impact during the vegetation period was estimated by calculating the area under the disease progress curve (AUDPC). The severity of leaf blotches in winter wheat leaves differed significantly during both vegetation seasons. Tan spot was the dominant disease in 2019 (18.7% in untreated variant). The development of tan spot was reduced by fungicide treatment; however, only in 2019, the influence of fungicide was significant. Septoria tritici blotch was the dominant disease in 2020 (11.4% in untreated variant), and its development was decreased by fungicides. Nitrogen fertilizer rate had no significant effect on the development of Septoria tritici blotches. Yield harvested in 2020 were significantly higher than those in 2019 (on average 5.23 t ha-1 in 2019, 8.40 t ha-1 in 2020). The using of fungicides provided significant increase of yield but there were no significant differences among fungicide treatment schemes

Possibilities of cucumber powdery mildew detection by visible and near-infrared spectroscopy

Received: July 16th, 2021 ; Accepted: November 6th, 2021 ; Published: February 1st, 2022 ; Correspondence: [email protected] are one of the most demanded and widely grown greenhouse vegetables. Important factors that influence quality and quantity of yield are diseases. Powdery mildew (caused by Podosphaera xanthii and/or Golovinomyces cichoracearum), is one of the most harmful cucumber diseases. Early detection of mildew via non-destructive methods can optimize schemes of fungicide application. The study aimed to find regularities in the reflected light spectra, indices described in the literature, and severity of mildew. Plants were grown in the polycarbonate greenhouse under artificial lighting in a 16 h photoperiod with PAR at the tips of plants 200 ± 30 µmol m-2 s-1. Leaf reflection spectra were obtained using spectroradiometer RS-3500 (Ltd. Spectral Evolution). Spectral range 350–2,500 nm, bandwidth 1 nm. The severity of cucumber mildew was evaluated using 10 point scale (0- no symptoms, … 9 - the plant is dead). The vegetation indices found in the literature have been calculated. The obtained results show that the calculated indices have different sensitivities. The strongest correlation between the degree of cucumbers infection with powdery mildew and the light reflectance spectrum was found in the green range of visible light around 550 nm. Disease-Water Stress Index-2 (DSWI-2), Structure Intensive Pigment Index (SIPI), and Normalized Difference Vegetation Index (NDVI) are the most suitable indices for determining powdery mildew in cucumbers. New indices for detection of powdery mildew have been created. None of the studied indices allows determining the powdery mildew at the early stages of disease development when powdery mildew severity is below 10%