The Effect of Harvest Date on the Chemical Composition and Fodder Yield of Guizotia abyssinica (<i>Guizotia abyssinica</i> (<i>L.f.</i>) <i>Cass.</i>) under the Climatic Conditions of South-West Poland

Guizotia abyssinica (Guizotia abyssinica (L.f.) Cass.) is regarded as a minor oilseed crop, which is important in terms of its nutritional value and potential uses. An important benefit of this crop is its cultivation for green matter and seed yield even under the difficult conditions of marginal cultivation. Guizotia abyssinica has not yet gained popularity in Europe. However, in a changing climate and taking into account its feeding value, it could gain in importance for ruminant nutrition in the near future. A field experiment was conducted in 2018 and 2019 in the west part of Poland on a farm in Opolskie voivodship (commune Prudnik). The objective of the field study was to assess the effect of three harvest dates on the yield and the chemical composition of fodder in a 90-day cultivation cycle in each year of the study. Stage of growth seems to be the most important factor affecting yield and the chemical composition of Guizotia abyssinica. In both years of the research, the green fodder yield reached the highest value after 90 days from sowing—32.5 and 36.9 t ha−1—while dry matter was 6.85 and 7.99 t ha−1, respectively. Chemical composition was also significantly dependent on harvesting date. Crude protein (in 2018 from 154.5 to 100.7 g kg−1 and in 2019 from 148.3 to 78.2 g kg−1) and crude ash (in 2018 from 165.8 to 98.7 and in 2019 from 155.2 to 89.9 g kg−1) content decreased with progressive harvest date while nitrogen-free extracts (in 2018 from 500.5 to 562.0 g kg−1 and in 2019 from 582.2 to 605.2 g kg−1) and gross energy increased (in 2018 from 19.4 to 21.17 MJ kg−1 and in 2019 from 18.63 to 19.73 MJ kg−1.). The most favorable date for harvesting green forage is 90 days after sowing, due to the significantly highest yield of fresh and dry matter of green forage and with potential as a forage for animals