M. B. Adjei

Agronomic characteristics of US 72-1153 energycane for biomass

Abstract Biomass production and plant quality vary between plant species and morphological components of a plant. The purpose of this two-part experiment was (1) to study the influence of energycane [ Saccharum sp. (L.) ‘US 72-1153’] harvest treatments (6) on dry biomass yield and (2) monitor changes in quantity and quality of plant components with increased plant height. Treatments for Part 1 determined the influence of plant height when harvested at 1.2, 2.5, and 3.7 m, mature stage in October (4.9 m, in flower), mature stage in December (4.9 m, in flower), and additional treatment harvested in October, which received half the total N (168 kg ha −1 ) on dry biomass yield from 1986 to 1989. Part 2 treatments were to monitor changes in quantity and quality (crude protein and in vitro organic matter digestion) of plant components (green leaf, dead leaf, and stem) at 0.6 m plant height increments to a final height of 4.3 m during 1986 and 1987. Treatments from both parts of the study received 25 kg P ha −1 and 93 kg K ha −1 in one application and 336 kg N ha −1 yr −1 in single or split applications applied prior to growth of each harvest. Plants repeatedly harvested at the 1.2 m height (Part 1) and mature stage produced a 4-year average yield of 10 and 48 Mg ha −1 yr −1 dry biomass, respectively and decreased in dry biomass yield 89% (1.2 m harvest) and 53% (mature harvest) between years 1 and 4. The stem (1986 and 1987) and dead leaf (1986) plant components increased quadratically as plant height increased, and green leaf decreased from 70% (0.6 m) to 17% (4.3 m height). The crude protein concentration decreased 51% (green leaf) and 81% (stem) and in-vitro organic matter digestion decreased 54, 32, and 34% for dead leaf, green leaf, and stem, respectively as plant height increased from 0.6 to 4.3 m. These data indicate that harvest management is an important factor for energycane biomass yield, ratoon-crop success and plant quality if biomass is used as a methane source.

Harvest management effects on quantity and quality of Erianthus plant morphological components

Lignocellulose materials can be readily produced under tropical and subtropical conditions and converted to a variety of fuels through bioconversion methods. However, biomass production and plant quality may differ between plant species and morphological components of plants. The objectives of these two experiments were to: (1) determine the influence of plant height at harvest on Erianthus arundinaceum (Retz) Jesw-IK76-110 dry biomass (DB) yield; and (2) monitor changes in tiller density, quantity and quality of plant components with increased plant height. Experiment (1) determined the influence of plant height when harvested at 1.2, 2.5 and 3.7 m, mature stage in October (4.9 m), mature stage in December (4.9 m, plus inflorescence), and an additional treatment harvested in October, which received half the total N (168 kg ha−1) annually on DB yield from 1987 to 1990. Experiment (2) treatments were to monitor changes in quantity and crude protein (CP) and in vitro organic matter digestion (IVOMD, estimate of soluble cell solids) of green leaf, dead leaf and stem plant components, leaf area index and tiller number at 0.6 m plant height increments to a final height of 4.3 m during 1987 and 1988. Treatments from both experiments of the study received 25 kg P and 93 kg K ha−1 in one application add 336 kg N ha−1 y−1 in single or split applications applied annually prior to regrowth of each harvest. Plants repeatedly harvested at the 1.2 m height and mature stage in December (Experiment (1)) produced a 4-y average yield of 5.2 and 51.5 Mg ha−1 y−1 DB, respectively. These same two treatments had a yield reduction of 100% (plants died) and 1% between years 1 and 4. Leaf area index increased quadratically to a maximum of 17 at the 3.1 m plant height treatment. Percentage green leaf, total tillers and live tillers decreased quadratically, while dead leaf and dead tillers increased linearly and stem increased quadratically as plant height was delayed from 0.6 to 4.3 m. Crude protein and IVOMD of green leaf and stem decreased quadratically with plant maturity. Knowing the quantity and quality of plant components at various physiological stages can be important to biomass producers, who need to make logical field decisions regarding biomass feedstock that should be utilized immediately after a freeze or stockpiled for later use.

AQUACULTURE EFFLUENT AS A WATER AND NUTRIENT SOURCE FOR HAY PRODUCTION IN THE SEASONALLY DRY TROPICS

In the water-limited environment of the U.S. Virgin Islands, tank culture of Tilapia (Oreochromis niloticus) is gaining importance. A by-product of intensive fish culture is a nutrient-rich wastewater (effluent). It is not known if effluent can replace the nitrogen (N) fertilizer required by guineagrass (Panicum maximum Jacq.) managed for hay. This study was conducted from 1997 to 1999 to compare the effects of irrigated aquaculture effluent (AE) and inorganic N rates of 60 kg ha1 (N60) and 0 (N0) on dry matter (DM) yield, forage crude protein concentration (CP), and in vitro organic matter disappearance (IVOMD), soil pH and phosphorous (P). Aquaculture effluent was applied at 2 cm ha1 wk1 to guineagrass for an 18-wk period in 1997 and 1999 but not in 1998. Guineagrass plots were harvested at eight-wk intervals (three eight-wk harvests in 1997, 1998, and 1999). Effluent DM yield (three harvests in 1997; 14.0 Mg ha−1) was similar (P > 0.05) to N60 (13.0 Mg ha−1). In 1998, effluent DM yield (three harvests; 13.7 Mg ha−1) was higher (P < 0.05) than N60 (9.8 Mg ha−1) suggesting a slow release N from the effluent. In 1999, AE out-yielded N60 by more than 50%. There was a trend for higher CP (9.6%) for the AE compared to (8.6%) for the N60 in 1997. In 1999, AE was two percentage units higher (P < 0.05) in CP (10.3%) compared to N60 (8.3%). In vitro organic matter disappearance in 1997 and 1999 were similar for all treatments and averaged 56% and 61%, respectively. There were no changes in soil pH (7.8) and P (22 mg kg−1), averaged across treatments. These results confirm that aquaculture effluent is an excellent N and water source for forages in the dry season and can replace the inorganic N requirements of guineagrass. The results should encourage the utilization of this effluent as a fertilizer rather than disposition to the environment.

Interactive Effect of Phosphorus and Nitrogen on Leaf Anthocyanins, Tissue Nutrient Concentrations, and Dry‐Matter Yield of Floralta Limpograss during Short Day Length

Abstract A field trial was conducted during the short‐day period of 2004–2005 at Ona, Fl., to study the factorial effect of nitrogen (67, 90, and 134 kg N ha−1) and phosphorus (0, 5, 10, 20, and 40 kg P ha−1) rates on forage dry‐matter yield, quality, nutrient uptake, and leaf pigment concentration of limpograss (Hemarthria altissima). The N and P fertilizers were applied 45 days before each of two harvests. There was no interaction between N and P rates on any of the measured variables. Cool‐season forage yield increased curvilinearly from 137 to 350 kg ha−1 in winter and 237 to 1389 kg ha−1 in early spring, whereas crude protein (CP) concentration increased from 145 to 158 g kg−1, as P was increased from 0 to 40 kg ha−1, but yield and CP were not affected by N rate. There was a decreasing linear relationship between leaf concentration of anthocyanins and P rate of application such that forage obtained with 0 kg P ha−1 had 61% more leaf anthocyanins and purple pigmentation than with 40 kg P ha−1. There was no effect of N on anthocyanins content. It was concluded that increased level of leaf anthocyanins was due to the cumulative stress from cool weather and lower plant‐tissue P levels, which resulted in reduced growth and yield of limpograss. In cool weather, P played a critical role in controlling leaf purple pigmentation and forage yield.