C. P. Brown

Influence of salinity in irrigation water on forage sorghum and soil chemical properties

Abstract Soluble salts found in wastewater can be toxic when used for irrigation of forages. Thus, two greenhouse experiments were conducted to investigate effects of saline [CaCl2NaCl (3:1, w:w)] treatments on soil chemical properties and ‘Dekalb FS‐5’ forage sorghum [Sorghum bicolor(L.) Moench]. Treatments for the first experiment consisted of a nonsaline control or 500 mL of a solution with an electrical conductivity (EC) of 10 dS m−1 applied once. In the second experiment, treatments were salinity levels of 1.7,3.5,5.2,8.5, and 12.2 dS m−1, applied in non‐nitrogenous Hoaglands solution as the sole source of irrigation. Both experiments were replicated four times. For both experiments forage sorghum was seeded in pots containing 7 kg of air‐dried Amarillo fine sandy loam soil. Sorghum survivability and plant height were measured. In the second experiment, water use by sorghum was also measured. Plants were harvested 7 wk after seeding, weighed, dried at 55°C, weighed, and ground for subsequent mineral...

RESPONSE OF BROMEGRASS TO NITROGEN FERTILIZATION. II. GRASSLANDS GALA

ABSTRACT Grasslands “Gala” (Bromus stamineus Desv.) bromegrass is generally regarded as high quality forage particularly adapted to grazing, but little is known about its growth response to N fertilization or potential to accumulate nitrate (NO3 −). Effects of N fertilization were investigated in two greenhouse experiments. Gala was grown in pots in a complete randomized design with four replications of the following N treatments: 0, 25, 50, 100, and 200 kg N ha−1 applied twice in Experiment 1, and 50, 100, 200, 300, and 400 kg N ha−1 applied five times in Experiment 2. Plants were harvested twice in Experiment 1, and five times in Experiment 2. Twenty-five kg N ha−1 per application did not sustain growth of Gala but little increase in growth occurred beyond 50 kg N ha−1 over five applications. About 90% of the 250 kg N ha−1 that was applied in 50 kg-increments was measured in the aerial plant biomass. Yield efficiency was also greatest at 50 kg N ha−1 per application and decreased with increasing N levels. Five applications of N at any rate tested decreased soil pH and increased accumulation of NO3 − in the soil. Nitrate accumulated in the plant at N application rates above 50 kg ha−1. Frequent low rates of N appear necessary to avoid N accumulation in soils, to promote high N use efficiency by Gala, and to avoid a potential for NO3 − toxicity to grazing ruminants.

RESPONSE OF BROMEGRASS TO NITROGEN FERTILIZATION. I. GRASSLANDS MATUA PRAIRIE GRASS

ABSTRACT “Matua prairie grass” (Bromus willdenowii Knuth) bromegrass is regarded as high quality forage particularly adapted to hay but may also be used for grazing. Little is known about the growth response to nitrogen (N) fertilization or its potential to accumulate nitrate (NO3 −). Effects of N fertilization were investigated in two greenhouse experiments. Matua was grown in pots in a complete randomized design with four replications of each N treatment. Nitrogen rates were 0, 25, 50, 100, and 200 kg N ha−1 applied twice in Experiment 1 and 50, 100, 200, 300, and 400 kg N ha−1 applied five times in Experiment 2. Plants were harvested twice in Experiment 1, and five times in Experiment 2. Twenty-five kg N ha−1 per application did not sustain growth. Matua tolerated up to 200 kg N ha−1 per application but little increase in growth occurred beyond 50 kg N ha−1 per application. Over five N applications, Matua recovered about 90% of the 250 kg N ha−1 that was applied in 50 kg-increments. Yield efficiency was greatest at 50 kg N ha−1 per application and decreased with increasing N levels. Five applications of N at any rate tested decreased soil pH and increased accumulation of NO3 − in the soil. Nitrate accumulated in the plant at N application rates above 50 kg ha−1. Frequent low rates of N appear necessary to avoid N accumulation in soils, to promote high N use efficiency by this grass, and to avoid a potential for NO3 − toxicity to livestock.