We evaluated the effects of Ν rate and two strategies of cattle manure (CM) application on dry matter yield (DMY) and nutritive value of bahiagrass (Paspalum notatum L. Fluege). The Ν rate treatments ...were 200 and 400 kg Ν ha"1 from CM or 50/50 CM plus ammonium nitrate (AN) combination, applied either in a single or split dosage. Bahiagrass was clipped at 28-d intervals for DMY, crude protein concentration (CP) and in vitro organic matter digestibility (IVOMD). First year results showed significant effects of application strategies and Ν rate. The combination of CM+AN performed better than treatments with CM alone. Dry matter yields of 6.67, 6.46, 5.73 and 6.27 Mg ha"1 were recorded for the 400 kg Ν ha"1 as CM+AN in single and split, and for the 200 kg Ν ha"1 as CM+AN in single and split applications, respectively. Comparatively, DMY of 6.38, 5.35, 5.98 and 4.82 Mg ha"1 were recorded for the 400 kg Ν ha"1 of CM in single and split, and for the 200 kg Ν ha"1 of CM in single and split applications, respectively. The 400 kg Ν ha"1 of CM+AN had the greatest IVOMD values of 547 and 543 g kg"1 for the single and split applications. Treatments receiving split application of CM had the lowest DMY, IVOMD and CP values. Phosphorus uptake and percentage recovery were also greatest for treatments that received CM+AN combination. Between 23 to 26% of the applied Ρ was recovered in the CM+AN treatments compared to 10 to 21% in the treatments that had CM alone. The results show that applying CM in combination with an inorganic nitrogen source can provide high forage yield of high quality and also reduce Ρ risk to the environment.
Guineagrass (Panicum maximum Jacq.), an important tropical forage in the eastern Caribbean Islands is established from seed. Low seed availability due to seed shattering losses and low germination ...percentages limits pasture development in the U.S. Virgin Islands. Recent introduction of Atra paspalum cv. Suerte (Paspalum atratum Swallen) exhibited potential as stand-over forage, but more information is needed on dry matter yield (DMY) and seed yield. A field experiment was conducted on a mildly alkaline Fredensborg clay (fine carbonatic, isohyperthermic, Typic Rendols, Mollisols) in 2000 to determine the effect of three N rates (0, 56, and 112 kg ha'1) on DMY and seed yield of guineagrass, Bluegrass, and Suerte. Ammonium sulfate as N source was broadcast applied on cut grass stands (15-cm stubble height) on 15th August 2000 and harvested in November 2000(12 wk). Guineagrass and Suerte differed in DMY (P<0.05). There was also an N linear (P<0.05) effect on DMY for guineagrass, but not for Suerte. Guineagrass DMY averaged 6.5, 8.3, and 9.4 Mg ha"1 for the 0, 56, and 112 kg ha"1 of N, respectively. Suerte averaged 2.56 Mg ha"1. Seed yield of guineagrass compared to Suerte was not different (P>0.05). Seed yield of guineagrass was 242 kg ha"1 and Suerte was 278 kg ha'. There was a trend for seed increase with increasing N rates for guineagrass (P=0.10) and a quadratic response (P<0.05) for Suerte. Results of the study indicate a strong response of guineagrass to N applications. During seed maturity, strong easterly winds may have affected yields of both grasses. Multiple harvests may be needed for these grasses to get a better estimate of seed yield and quality.
Forage quality and quantity from palatable grasses, like creeping bluestem Schizachyrium scoparium (Michx.) Nash var. polycladus (Schriber and Ball) Bruner (Syn S. stoloniferum Nash.), are limited, ...especially in winter when cows graze Florida range. We anticipated that N fertilizer (0, 40, 60, 120 kg ha(-1)), P (0, 25 kg ha(-1)) and K (0, 100 kg ha(-1)) would increase bluestem yield, tiller density, and forage quality. Within sample dates yield and tiller density increased linearly with N rate. For example 31 days after fertilization, intercepts for equations predicting yield were 319 kg ha(-1) and 124 m(-2) with coefficients of 1.2 and 0.29, respectively, where the independent variable is N rate. Over sample dates yield responses to N rate were quadratic and tiller densities were cubic. Reproductive tiller density was increased by N fertilization (1989 tiller density, no. m(-2), = 30 + 0.29N). Neither yield nor tiller density was affected by P fertilizer, but K fertilizer increased reproductive tiller density, hence fall yield. After 3 years of fertilization, N had negative quadratic and negative linear effects on yield and tiller density, respectively. Tissue N concentration in the fall was reduced with N fertilization because of increases in reproductive growth (1988 calendar 145 days postfertilization, g kg(-1) = 5.7 - 0.041 N + 0.00031 N(2)). Fertilization of creeping bluestem is not a recommended practice when bluestem is to be grazed in fall and winter.
Field and greenhouse studies were conducted in Pomona fine sand with low initial P status that was limed and amended with various rates of P. An attempt was made to equalise VAM inoculum densities in ...these studies, but the time required to conduct most-probable-number assays was sufficient for significant changes in propagule density to occur. The VAM fungi generally failed to be above the critical level for maximum biomass production in all treatments. Nonetheless, some differences were found in plant cover suggesting that selected strains of VAM fungi may be important in establishment. In a study where soil type was evaluated, colonisation was obtained even at shoot-P concentrations greater than 5 g per kg, indicating that shoot-P concentration was not the only factor inhibiting colonisation in the Pomona soil. The results suggest that pH may have also limited colonisation and that future work with the plant should include VAM isolates tolerant of acid soil environments.
Phosphogypsum is a by-product of the manufacture ofphosphoric acid from phosphate rock and is a potential source of sulfur and calcium for crops. There are currently more than 700 million Mg of ...phosphogypsum in Florida alone stacked in waste piles and an additional 30 million Mg produced annually. A field study was conducted to determine whether addition ofphosphogypsum to bahiagrass would increase production and quality. Results indicate that addition ofup to 4.0 Mg/ha phosphogypsum increased bahiagrass yields, protein content. and in vitrodigestibility offorage. This study has demonstrated that phosphogypsum can be used as an alternative source of sulfur and calcium for forage crops.
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