Effects of different chemical additives on drying characteristics, microstructure, nutritional quality, and fungal diversity of Egyptian clover hay during storage

Egyptian clover ( Trifolium alexandrinum L.) is a high-yield and high-nutrition legume forage crop. However, traditional natural drying methods are inefficient, cause severe nutrient loss, and pose a high risk of fungal contamination. Little is known about the dynamic changes in its hay quality, fungal community, and microstructure during storage with the addition of chemical additives. This study aimed to evaluate the effects of ten chemical additives (a natural sun-drying control [CON] and different mass fractions of NaHCO 3 [1%, Na1; 2%, Na2; 3%, Na3], K 2 CO 3 [1%, K1; 2%, K2; 3%, K3], and CaCO 3 [1.5%, Ca1; 2%, Ca2; 2.5%, Ca3]) × four storage times (0, 30, 60, and 90 d) on the dehydration efficiency, nutritional quality, and fungal communities at 0 and 90 d of storage in Egyptian clover hay. The results showed that K3 and Na3 significantly shortened the drying time from 72.0 h to 54.7 h ( P < 0.0001), representing a 24.0% reduction compared to CON. Ca3 significantly decreased the leaf loss rate by 26.1% ( P = 0.006) relative to CON, and K1 and Ca3 significantly increased the crude protein content by 27.6% and 26.8%, respectively ( P < 0.0001). After 90 d of storage, Na3 had the lowest total fungal count (4.34 log 10 CFU g − 1 FM), effectively inhibited the proliferation of spoilage-associated fungal genera such as Aspergillus and Wallemia , and altered the dominant fungal community dominated by Vishniacozyma and Alternaria . Grey relational analysis confirmed that K3 had the highest comprehensive relational grade (0.809) and best overall performance. The results suggest that 3% K 2 CO 3 is a promising practical additive for Egyptian clover hay production, mainly by accelerate dehydration through cuticle-related physical changes and by helping maintain nutritional quality and fungal community characteristics during storage.