Dry Mass Yield and Bromatological Composition of the Forage of Cynodon dactylon cv. Vaquero Submitted to Crescent Doses of Nitrogen, Applied as Swine Waste

The present had as its objective to evaluate the response of dry mass total yield, and bromatological composition of the forage, submitted to different nitrogen doses, applied as swine waste in the pasture of Cynodon dactylon cv. ‘Vaquero’. The study was developed during the period of November 2017 until March 2018, in the experimental area of the ‘Pontifícia Universidade Católica do Paraná’, campus Toledo, located in the western region of Paraná, under latitude 24o43′13′′ S and longitude 53o47′01′′ W. The experimental design adopted was of randomized blocks with six treatments (0, 50, 100, 150, 200 and 250 kg ha) constituted by crescent doses of nitrogen as swine waste, with five replicates, totalizing 30 experimental plots. It was studied the dry mass yield (kg ha), crude protein (CP), dry mass (DM), neutral detergent fiber (NDF), acid detergent fiber (ADF), insoluble nitrogen in neutral detergent (NDIN), insoluble nitrogen in acid detergent (ADIN), lignin, ether extract (EE) and mineral matter (MM). It was verified that the N doses influenced in the dry mass yield of the forage, because it reached a productivity of 4520.57 kg ha in the dry mass. The highest crude protein content of ‘Vaquero’ was obtained with the dose of 250 kg ha of nitrogen, in which was observed a content of 13.72 g kg of CP in the dry mass. The different nitrogen doses, applied as swine waste in the pasture of grass ‘Vaquero’, have an influence in the bromatological composition and in the dry mass yield, causing an increase in the forage contents of crude protein (CP), dry mass (DM), ether extract (EE), in forage produced under four cutting periods. The increase in the nitrogen doses improves the nutritional quality of grass ‘Vaquero’, once it causes decreases in the NDF and ADF content and increases in the CP and DM content.

The grass 'Vaquero' was already planted in the experimental area, its past use was to produce hay. In 11/10/2017 it was cut and uniformized, with aid of mower, plants were cut at 0.05 m in relation to the soil surface and, the material obtained with the cut, was removed with a garden rake. Finishing the cut, the area was delimited, and the experimental plots were dimensioned with wooden stakes.
Thirty days after the uniformization cut, the first evaluation of the grass 'Vaquero' was made, with the following ones being made in an interval of 30 days, totalizing four cut periods. After each cut realized for the evaluations, it was repeated the nitrogen fertilization, in function of doses applied as swine waste. A graduated bucket was used to measure the wastes volume to be applied, in different doses in the plots, according to their respective treatment ( Table 2).
The application was made with a watering can with rose, so the liquid was poured in a shower. The swine wastes used for the fertilization were removed from a biodigester of a swine production farm. The property is located next to the experimental area.
The waste was transported from the farm to the experimental area with a 4000 liters waste distributor tank. After transport, the material was homogenized, being about 2 liters separated for lab analysis. Table 2. Amount of nitrogen (t ha -1 ) as swine waste (L ha -1 ), applied in four cut periods  Source: The author, 2018.
The lab analysis was made in the 'Laboratório de Análise Ambientais e Agronômicas' in Campo Mourão-Paraná. The nitrogen concentration from the waste's analysis in the four cut periods are shown on Table 3. The determination of the amount to be applied in the plots was based in the nitrogen content of the waste analyzed. In the sampling two metal squares of 0.5 × 0.5 m (0.25 m²) were used, which were randomly thrown on each experimental plot. After thrown, all the plants inside the square were collected, being the cut made with a scythe.
After every collection the plants were packed in plastic bags, taken to the animal nutrition lab from the "Pontifícia Universidade Católica do Paraná", and weighted for the fresh mass obtainment.
After weighing, one subsample of 200 g was stored in paper bags and taken to an air forced circulation oven at 55 ºC for 72 hours for the dry mass determination (Silva & Queiroz, 2006). The total dry mass yield was obtained by the multiplication of the fresh mass yield for the dry mass content.
The material from the oven were mowed in an Willey type mower, with 1 mm sieve, after the material was mowed it was stored into identified plastic containers for posterior chemical analysis, for the determination of: dry mass content (DM), crude protein (CP), ether extract (EE) and ashes (AS), according to the methodology described by AOAC (1990) and neutral detergent fiber (NDF), acid detergent fiber (ADF) and lignin following the methodology describe by Van Soest et al. (1991). The samples from the NDF and ADF analyses allowed the evaluation of insoluble nitrogen in neutral detergent (NDIN) and insoluble nitrogen in acid detergent (ADIN).
From the data obtained were calculated the average values for the four periods evaluated, about the effect of the nitrogen doses in productivity and in the bromatological composition, by means of regression analysis, testing the linear and quadratic models. For the choice of the model, it was considered the parameters significance (P < 0.05) and the determination coefficient (R²). All analysis was made with the software SigmaPlot 12.0 (Systat Software, 2011). jas.ccsenet.

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