Mitigação do déficit hídrico utilizando a fertilização com silício e inoculação Azospirillum brasilense na produtividade e no valor nutritivo do milheto na forma de silagem na entressafra agrícola

Abstract

The objective was to evaluate the effect of mitigating water deficit using silicon fertilization and Azospirillum brasilense inoculation on the productivity and nutritional value of millet in the form of silage in the agricultural off-season. A randomized block design was used in a 4 × 2 factorial scheme with five replications, evaluating four doses of silicon applied via fertilization (0, 4, 8 and 12 kg ha-1) in combination with the inoculation or not of Azospirillum brasilense. The cultivar used was millet (Pennisetum glaucum (L.) BRS 1501. Regarding productivity and morphoagronomic characteristics, water accumulation (AC) (kg/ha), plant height to flag leaf (ALFB), height of plant (AP), panicle length (CP), stalk diameter (DC), panicle diameter (DP), water use efficiency (WE) (kg /DM/ mm/ ha), stalk dry matter ( MSC), leaf dry matter production (MSF), panicle dry matter (MSP), number of reproductive tillers (NPR), number of vegetative tillers (NPV), stalk production (PCH) (kg/ha), production stalk dry matter production (PMSCOL), leaf dry matter production (PMSF) (kg/ha), grain production (PGHA), dry matter production (PMS) (kg/ha), stalk dry matter production (PMSC) (kg/ha), leaf dry matter production (PMSF) (kg/ha), panicle dry matter production (PMSP) (kg/ha), green matter production (PMV) (kg/ha ), panicle weight (PP), leaf:stalk ratio (RFC). Millet silages and millet-based total feed silages were produced to meet the requirements of beef cattle and dairy goats. After 120 days, the silos were opened and the silages were analyzed for their fermentative quality, microbial population, dry matter recovery and bromatological chemical composition of the silages. For the productive characteristics, interaction effects (P<0.05) Si x Azospirillum were observed for the variables MSF, MSP, RFC, leaf, stem, NPV, APFB and DC constituents. Isolated effects were observed for inoculation with Azospirillum brasilense (P<0.05) on the buffer capacity of all silages evaluated. For total feed silages for beef cattle, Si doses (0, 4, 8 3 12 kg ha-1) showed an isolated effect on pH (P<0.05). Microbial populations, including lactic acid bacteria, molds and yeasts, showed interaction effects between inoculation with Azospirillum brasilense × silicon doses (P<0.05). Silages produced with material inoculated with Azospirillum brasilense showed, in general, higher counts of lactic acid bacteria. The yeast population was significantly lower in both total feed silages (P<0.05). The chemical composition of the silages showed isolated effects for the dose of silicon (P<0.05), causing a decrease in ADF levels with the highest doses of Si (8 and 12kg ha-1) included in the silages of total feed for cattle. The 12kg ha-1 dose of silicon and inoculation with Azospirillum brasilense when combined were efficient in improving the productive and morphological characteristics of millet. The use of millet silage and total feed proved to be a promising and viable strategy for feeding beef cattle and dairy goats. The results obtained indicate adequate fermentation patterns, microbial populations and chemical-bromatological composition even with the use of silicon and Azospirillum brasilense in millet production, thus suggesting this nutritional combination in total feed diets for the production of beef and goat milk.