Zālāju ražas noteikšanas iespējas, izmantojot ģeotelpisko informāciju = Grass yield estimation opportunities using geospatial information

An essential part or 21% of Latvia’s total agricultural land is made up of perennial grasslands, according to Central Statistical Bureau (CSB) information in 2021. The information on the yield from grasslands is important both for implementing agricultural policy and solving economic issues. However, more detailed information on long-term grassland yield is not available because of complexity and inaccuracy of the grassland yield evaluation process. Therefore, in 2022 within the framework of the CSB pilot project recommendations for the methodology of grass yield estimation, the normalized difference vegetation index (NDVI) of the Copernicus Sentinel-2 mission (European Space Agency) was developed. The measurements of grassland productivity were carried out in grasslands grouped by age into 5 groups (1–3 years; 4–5; 6–10; 11–19; and >20 years). The obtained relationship between the dry matter yield of the grass and NDVI with 40% correspondence (R2=0.409) was analysed using the linear regression. The results of the research of individual age groups of grasses revealed a very close relationship (R2=0.886) in the first half of the vegetation period between the NDVI index and the dry matter yield of grasses in the oldest group of 20 years and more. As regards the second half of the vegetation period in the surveyed grasslands, the relationship between the NDVI index and the dry matter yield of grasses was not found, i.e., the coefficient of determination (R2=0.173) indicated only 17% compliance with the obtained results. The reason of the weak relationship in the grasslands surveyed in August was the different development stage of the grasslands.