Persistence of auxinic herbicides applied on pasture and toxicity for succeeding crops.

The aim of this work was to determine the persistence of auxinic herbicides applied on tropical pasture and toxicity for succeeding crops. The herbicides were applied in an area of dystrophic red‒yellow latosol with pasture infested of weeds. At 40, 80, and 280 days after application of herbicide, the soil samples were collected at depths of 0 to 20 cm. Soil with residues of 2,4-D, 2,4-D + picloram, triclopyr, and a soil without herbicide application were analyzed with six replicates. Seven crops were cultivated in these soils: cucumber (Cucumis sativus L.), velvet bean [Mucuna pruriens (L.) DC.], pigeon pea [Cajanus cajan (L.) Millsp.], alfalfa (Medicago sativa L.), lablab bean [Lablab purpureus (L.) Sweet], corn (Zea mays L.), and sorghum [Sorghum bicolor (L.) Moench]. The plants of cucumber, pigeon pea, and alfalfa were the most susceptible to the auxinic herbicide residues. However, the lablab bean was the only one among the dicot evaluated that showed tolerance to the 2,4-D + picloram residual when cultivated in soils at 280 days after application of herbicide. Corn and sorghum showed lower chlorophyll content in soils with 2,4-D + picloram residual up to 80 days after application of herbicide.

Intake, apparent digestibility, rumen fermentation and nitrogen efficiency in sheep fed a tropical legume silage with or without concentrate.

Legume silage can increase the forage quality of the diets as well as supply it with nitrogen, calcium and phosphorus. The objective was to evaluate the intake, apparent digestibility, rumen fermentation and nitrogen efficiency in sheep fed a tropical legume silage with or without concentrate. Twelve crossbred sheep with an average initial body weight of 32.2 ± 1.26 kg, with six animals cannulated in the rumen were distributed into four 3 × 3 Latin squares. The treatments were 1) Stylosanthes silage without concentrate (StS), 2) Stylosanthes silage with concentrate (StS+C), and 3) corn silage with concentrate (CS+C). StS diet showed lowest intake, except for neutral detergent fiber (NDF). The diets StS+C and CS+C showed similar intake of dry matter (DM) and crude protein. The intake of total digestible nutrients was higher for CS+C diet than diets StS+C and StS. Animals fed CS+C diet had lowest ruminal pH. The nitrogen use efficiency was similar for the diets with concentrate. In conclusion, StS+C diet replacing CS+C diet decreases the intake of total digestible nutrients.