The effect of the moisture availability rate on the productivity and nutritional value of sorghum crops

Productivity reduced by drought is quite common. There can be up to 60.0% of the harvest losses. This is especially true for forage crops. The purpose of the current work was to identify the dependence of productivity and quality of green mass of sorghum crops on moisture availability during a vegetation period of plants. Sudan grass variety Alice, sugar sorghum variety Yuzhnoye, and sorghum-sudangrass hybrid variety Gustolistny were used as research objects. The study was carried out in the Rostov region. The soil of the experimental plot was ordinary carbonate black earth (chernozem). In order to study the variability of productivity and nutritional qualities, the years with the HTC level from 0.34 to 0.88 with an interval of 0.8–1.2 (2018–2022) were taken into account. The trials were conducted according to the methodology of the State Variety Testing. When the HTC increased from 0.34 to 0.88, there was a tendency to improve green mass productivity by 23.3–35.0% and decrease the protein percentage by 41.80–55.54%. A negative relationship between the amount of crude protein and the HTC value was revealed ( r = –0.78... –0.92). The digestible protein yield decreased by 22.22–31.03% with increasing moisture content. The largest mean value was identified for the sorghum-sudangrass hybrid with 0.70 t/ha and the sweet sorghum variety with 0.71 t/ha. The variation coefficient of fiber content was 2.16–5.42%, which indicated weak variability of the trait over the years, and, consequently, a weak dependence on the moisture availability rate, which was confirmed by the correlation analysis ( r = –0.03...0.32). The largest value of the metabolic energy was found in the sorghum-sudangrass hybrid (10.42–10.80 mJ/kg). At the same time, there was no dependence of this indicator, as well as the amount of feed units, on the moisture availability rate. The highest amount of digestible protein per feed unit was identified in sweet sorghum (83.4 g). A tendency to decrease this indicator by 22.6–42.5% was found as the HTC level increased ( r = –0.69...–0.90).