Production and quality of forage grasses under two N levels and water regimes

Forage crops are frequently subjected to nutritional stress and drought in areas where fertilizers are costly and water availability is either inadequate or short during irrigation. The facts that forages are grown under these stresses constitute an important resource in animal production. Objective of the study was to determined the effect of N (50 kg N vs 100 kg N ha-1) and irrigation (rainfed vs. irrigated) on growth and quality of grass species (barley, oats and ryegrass) commonly cultivated in the subtropical areas during winter as sole or in mixture with cloven. Barley, oats and ryegrass were cultivated on October 21, 1995 and sampling was made on different occasions during three Consecutive cuts in a period of 180 days after sowing (DAS). The growth function "Logistic equation " was fit to get the smooth sigmoid curves of the species dry matter production (DM). Quality analysis were carried out on alternately harvested weekly samples for determination of ash, crude protein (CP), in vitro dry matter digestibility ("MD), neutral detergent fiber (NDF), and acid detergent fiber (ADF). Not surprisingly, the high supply of water as well as N positively increased species DM but the DM production was not significantly influenced in the crop first growth. For all species high N supply affected DM during the re-growth stronger than the first growth. Overall effect of the N was higher on ryegrass DM, followed by barley and oats. Irrigation compared to rainfed mirrored similar but significant response of DM like the N treatment. Crop leaf area index mimicked DM production pattern regarding species growth and re- growths. Tillering per plant was high under irrigation and similarly reflected under high N application. Regarding quality parameters of the species, higher N application showed slightly increase in CP, IVDMD, NDF and ADF contents of the species in comparison to that of the low N fertilization rates. Similarly, irrigated crops showed higher values of CP, IVDMD, NDF and ADF when compared with the drought treatment. Comparison of the irrigation with N showed that watering increased all quality parameters greater than that of did by higher N supply in crop growth as well as in the re-growths. In case of quality parameters, the treatment irrigation effect was found stronger than the treatment N during the crop growth as well as in the re-growths in all species.