Effect of Nitrogen Fertilizer Rate and Harvest Season on Forage Yield, Quality, and Macronutrient Concentrations in Midland Bermuda Grass
Bermuda grass [Cynodon dactylon (L.) Pers.] is a major forage for grazing and hay production in the southern United States. The objectives of this study were to determine effects of nitrogen (N) fertilization rate (0, 112, 224, 336, and 448 kg ha−1), split spring and summer applications of N at the 224 and 448 kg ha−1 rates, and harvest periods (spring and summer) on forage yield, crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), total digestible nutrients (TDN), and concentrations of phosphorus (P), potassium (K), magnesium (Mg), and calcium (Ca in Midland Bermuda grass. Data were collected from 2002 to 2008 as part of an ongoing, long-term soil fertility experiment in southern Oklahoma. Repeated measures analysis of these long-term data showed that forage yield responses to N rate varied with year and harvest time with up to 2.5-fold yield differences among years. Nitrogen fertilization increased CP, TDN, and macronutrient P and Mg and decreased ADF and NDF. Crude protein was increased by ≥50%, and ADF and NDF dropped by up to 25% with the greatest N rate. In general, split N applications did not affect forage yield but produced low-quality forage compared to single N application in spring. Split application of 448 kg N ha−1 gave forage with CP, TDN, ADF, and NDF similar to the Bermuda grass receiving 336 or 448 kg N ha−1 as a single application. Spring forage had better forage quality than summer harvests. While N fertilization increased forage Mg and P concentrations by more than 50% during both spring and summer, it had no effect or slight increased K and Ca concentrations. In the southern Great Plains, despite the weather-dependent variability in forage yield of Bermuda grass, N application increase forage quality.
Effects of fertilization and tillage system on growth and crude protein content of quinoa (Chenopodium quinoa Willd.): An alternative forage crop -
A field experiment was conducted to determine the effects of fertilization and tillage on growth, yield and quality of quinoa crop (Chenopodium quinoa Willd.). The agronomic performance and nutritive value of quinoa was analyzed in order to define alternatives to local forages for dry-season feeding of ruminants in the Mediterranean region. The experiment was laid out in a split-plot design with two replicates, two main plots [conventional tillage (CT) and minimum tillage (MT)] and sub-plots (fertilization treatments: control, cow manure, inorganic fertilization 100 kg ha-1 (N1) and inorganic fertilization 200 kg ha-1 (N2)). The results indicated that quinoa growth was influenced by both tillage and fertilization. The lowest height and dry weight were found under MT. Moreover, the lowest height and dry weight (8205 kg ha-1 and 8020 kg ha-1 for CT and MT, respectively) were found under control treatment (no-fertilization). Concerning the nitrogen content there were no significant differences between CT and MT systems. In addition, the highest quinoa nitrogen content was observed for N2 treatment (200 kg N ha-1). Moreover, the highest nitrogen content was measured at 150 DAS. Concerning the crude protein content, there were no significant differences between CT and MT systems. In addition, there were significant differences in crude protein between fertilization treatments. The greatest value was observed for N2 treatment. Moreover, the highest crude protein yield (2481 kg ha-1 and 2356 kg ha-1 for CT and MT, respectively) and acid detergent fibre (ADF) were found under N2 treatment. In addition, ash was not influenced by both tillage systems and fertilization treatments. Data indicate that quinoa crop could be used as alternative to legumes for protein production to feed ruminant animals.
Dinâmica do acúmulo de matéria seca em pastagens de Tifton 85 sob pastejo
Herbage dry matter accumulation from forage plants results from the balance between growth and senescence. Agronomic practices may influence both processes in different ways and, therefore, alter the quantitative and qualitative patterns of dry matter production. This study aimed at evaluating the process of dry matter accumulation through measurements of growth and senescence. Experimental treatments corresponded to four sward state conditions (5, 10, 15 and 20 cm of sward surface height - SSH) generated by sheep grazing under continuous stocking and variable stocking rate. The experimental design was a complete randomised block, with four treatments and four replicates. Pasture responses evaluated were: stem elongation, leaf lamina elongation, senescence, phyllochron and number of leaves per tiller. The results showed a seasonal pattern of herbage production with the highest growth and senescence rates observed at the highest SSH studied (15 and 20 cm). Phyllochron varied according to time of the year and SSH, revealing an intimate relationship with air temperature variation, soil water availability and sward leaf area index. SSH of 15 and 20 cm resulted in the highest dry matter production. The same principles and relationships originally described for herbage accumulation in temperate grass pasture species are valid for tropical areas within the framework of the physiological and environmental constraints inherent to each condition.