Synopsis
Orchardgrass, fertilized with 500 pounds per acre of elemental nitrogen annually, produced the highest 2‐year average forage yields. Compared to the 500‐pound per acre rate, the application of 1000 pounds of elemental nitrogen generally reduced the yields of orchardgrass, timothy, and bromegrass. Grass‐legume mixture yields were higher with timothy than with bromegrass or orchardgrass. Interactions between grass species and treatments and differences between strains within species were significant.
Plastic mulch or polyethylene film has been used experimentally as a ground cover to hasten development for a number of crops. In this research attention was given to its potential use for sweet corn (Zea mays L.) as related to cultivar and insolation.
Two sweet corn hybrids with a 15‐day range in relative maturity were grown in 2 years under a clear plastic mulch in northern Wisconsin for comparison with traditional culture at that location and in the south central part of the state. Soil temperatures at a 7.6 cm depth were recorded by thermographs with bulb elements and related to official air temperatures. The periods from planting until silking and harvest were measured in terms of days and thermal units.
Silking and harvest dates were advanced on the average by 6 days and up to 9 days with the use of a plastic ground cover. The effect of plastic was relatively greater during cool days, on minimum temperatures, and in the cool year. Its effect was greater earlier in the season and for the smaller hybrid, because of less plant shading.
Fewer thermal units, although more days, were required to achieve comparable maturity at the northern as compared with the southern location in the cool year, but more thermal units as well as days were required at the northern location in the warm year. While maturity advanced more rapidly with increasing temperature, the advance was not directly commensurate with air temperature on a diurnal, seasonal, or locational basis.
Synopsis
Timothy produced more dry matter than bromegrass and orchardgrass when grown in pure stands without nitrogen fertilizer and in association with trefoil‐red clover. Orchardgrass was the most productive of the nitrogen‐fertilized pure grass stands cut at the pasture stage. Bromegrass yielded slightly more than timothy and orchardgrass in the alfalfa‐ladino association and in nitrogen‐fertilized stands managed as hay. Crude protein production was usually in the following order: bromegrass, timothy, and orchardgrass.
Synopsis
Increasing plot length was more efficient than increasing plot width to reduce variation among plots for forage yield of alfalfa‐bromegrass mixtures. Estimates of optimum plot size and replicate number to detect differences among treatments were similar, using the coefficient of variability and Smith's b. Greater efficiency and less variation in the relative costs of plots of different sizes were observed for the lattice as compared with the randomized complete block designs.
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