Utilização de polímeros retentores de umidade no solo sobre o déficit hídrico e avaliação da qualidade de silagens de milho e sorgo produzidas na forma convencional e como silagem de ração total

Abstract

Corn and sorghum are grasses of high nutritional value, traditionally used as forage for ruminants. However, their cultivation faces challenges in regions with irregular rainfall and long dry periods, which limit grain and biomass production throughout the year. In this context, strategies such as the application of soil moisture-retaining polymer (MRP) and the use of total mixed ration (TMR) silage ensure a continuous

supply of quality and sufficient food for these animals, even during the agricultural off- season. The objective of this study was to evaluate the effect of applying an MRP to

the soil on water deficit and the quality of corn and sorghum silages, produced in conventional (CS) and total mixed ration forms. The experiment was conducted in a 4 × 2 × 2 factorial design, consisting of four hydration intervals with MRP: control (no hydration), hydration only on planting day (H0), hydration every five days (H5), and hydration every ten days (H10), two crops (corn and sorghum), and two types of silage (CS and TMR). The experimental design used was randomized blocks, totaling 16 treatments and 64 experimental subunits. The fermentative profile (pH, buffering capacity (BC), ammoniacal nitrogen (N-NH3), and soluble carbohydrates (CHOs)), effluent losses (EL), and gas losses (GL), dry matter recovery (DMR), aerobic stability, and bromatological composition were evaluated. There was an interaction effect between the factors for the CHOs variable (P= 0.0233), with the highest mean obtained with the use of sorghum, associated with the use of CS and hydration with MRP every 10 days. Regarding isolated effects, there was a difference between treatments (P<0.05) for crop type and silage type for variables related to fermentative quality. Sorghum silage showed lower pH (3.86) and higher BC (0.1050 mg NaOH/g DM) compared to corn. The use of TMR provided higher pH (4.04), higher BC, and higher N-NH3. Regarding losses, TMR stood out for presenting lower EL and GL and higher DMR, compared to CS. For MRP, there was a difference for N-NH3 and EL variables. The lowest levels of N-NH3 and EL were observed with the use of MRP every 10 days of hydration. As for the bromatological composition, corn silage showed lower NDF levels (41.31%) compared to sorghum (52.81%). TMR showed higher levels of DM, Ash, and CP, while CS showed higher levels of EE, NDF, and ADF. The application of MRP to the soil promoted an increase in the total biomass production of corn and sorghum crops, with the hydration interval every 10 days being the most indicated for higher yields. Sorghum stood out for higher effective degradability (ED) and biomass production, being more efficient than corn, whose silage deteriorates more quickly. Therefore, the use of sorghum with ten days of hydration and retention time (SRT) is recommended for better nutritional value and diet utilization