Low Nitrogen Rates Research Articles

Influence of Nitrogen Fertilization, Gapping, and Burning on Seed Production of Newport Kentucky Bluegrass1

AbstractA study was conducted to determine the influence of nitrogen fertilization, gapping and burning on the seed yields and age‐associated seed yield decline of ‘Newport’ Kentucky bluegrass (Poa pratensis L.). The bluegrass was grown in rows under furrow irrigation. Treatments were applied in a split‐split plot design. Increasing the rate of nitrogen fertilization increased seed yields, seed weight per panicle, panicle numbers, and weight of 100 seeds. Weight of 100 seeds was least affected. Gapping by removing alternate 30‐cm sections of the row in late summer of alternate years reduced panicle numbers but increased seed weight per panicle in the year following treatment. Panicle numbers were reduced more by gapping at high than at low rates of nitrogen fertilization. Seed yields were increased by gapping at the low nitrogen rates but not at the high rates. Burning yearly after harvest had variable effects. The drop in seed yield associated with increased stand age was not prevented by any treatment.

The effects of a wide range of nitrogen application rates on the yields from a perennial ryegrass sward with and without white clover

SUMMARYA series of twenty-one nitrogen fertilizer rates ranging from 0 to 800 lb nitrogen/acre (897 kg/ha)/annum was applied on a pure S. 23 perennial ryegrass sward and on an S. 23 ryegrass sward containing S. 100 white clover. Total yields of herbage dry matter and crude protein from both swards at all the nitrogen rates were determined each year by cutting the herbage five times at approximately the same stage of growth on each occasion. Four-parameter growth curves relating herbage yield to nitrogen rate were fitted to the data, and are presented for the first 3 years of the experiment. On the pure-grass sward the response of dry-matter yield to nitrogen rate was almost linear between the 0 and 300 lb nitrogen/acre (336 kg/ha) rates, then it decreased steadily, becoming non-significant about the 500 lb/acre (560 kg/ha) rate. In contrast the response of crude-protein yield was virtually linear from the 0 to the 600–700 lb nitrogen/acre (673–785 kg/ha) rates. The inclusion of white clover in the sward increased the yields of dry matter and crude protein at the low nitrogen rates, but decreased the responses, with the result that the yields and responses of the grass + clover sward were not significantly different from those of the pure-grass sward at nitrogen rates above about 300 lb/ acre (336 kg/ha). In terms of profitability at present fertilizer prices the optimum nitrogen rate for dry-matter production on both swards was estimated to be 400–450 lb/ acre (448–504 kg/ha), whereas that for crude-protein production was greater than 600 lb/acre (673 kg/ha). The value of clover in a sward receiving nitrogen fertilizer is discussed.

Effects of time and rate of nitrogen application on tillering, ‘sharp eyespot’ (Rhizoctonia solani) and yield in winter wheat

SUMMARYVarious rates of nitrogen fertilizer were applied in early and late spring to two densities of winter wheat to examine their effects on grain yield and its components. A severe attack of ‘sharp eyespot’ (Rhizoctonia solani) allowed an assessment of the effects of the treatments on the incidence of this disease.The disease level was much higher where nitrogen was applied early and increased with increase in nitrogen up to 120 units applied; it was slightly higher at the higher density. Grain yield was slightly greater where nitrogen was applied late; early application gave more, but smaller, ears. Main shoots produced at least 70% of the grain in the high-density plots but less than 50% at the low density. Tillers appearing after early March contributed little to grain yield at the higher density but substantially at the lower one. Tillers produced after early April died without heading. In general, the chances of survival of a tiller diminished with delay in the time of its appearance, but some early tillers died while later ones survived and produced ears. The chances of survival of later tillers were greater at low density and high rates of nitrogen.

Leaf Area Indices and Nitrogen Uptake of Flue‐Cured Tobacco as Affected by Plant Density and Nitrogen Rate1

AbstractEffects of three plant densities and two nitrogen rates on leaf areas and nitrogen uptake by tobacco plants were studied during 1961 and 1962. A study was also made on the economics of these treatments.Leaf area indices (LAI's) for both years increased with time until the reduction in total leaf area through loss of senescent lower leaves became greater than the gain in leaf area of the active upper leaves. The highest maximum LAI of 5 in 1961 was obtained for the high nitrogen rate and the 25‐cm spacing. The lowest maximum LAI of 2.5 was obtained for the low nitrogen rate and the 76‐cm spacing. LAI's increased with high nitrogen and at both levels of nitrogen the LAI's were in the order of 25 > 51 > 76‐cm spacings in 122‐cm beds.Relationships between leaf area and leaf weight per plant were very similar during 1961 and 1962. Correlation coefficients for leaf areas and weights varied from 0.95 to 0.99 in 1961 and from 0.92 to 0.99 in 1962. In both years, better correlation appeared between leaf areas and weights at the high nitrogen rate than at the low nitrogen rate, with spacing treatments having little effect on the relationships.Nitrogen uptake was much higher with the high nitrogen treatment than with the low nitrogen treatment.The yield of flue‐cured tobacco increased with closer plant spacing and the higher nitrogen rate. However, leaf quality decreased with the high nitrogen rate and offset the higher yields in total dollar value per hectare. The quality of tobacco appeared to be influenced more by the nitrogen application than by the different plant spacings~ The most profitable treatment combination appeared to be the 76‐cm spacing at the low nitrogen rate.

The effect of herbicides, anhydrous ammonia and seed ing rate on winter production of oats sod-sown into grass dominant pasture

A factorial field experiment, comparing three rates of nitrogen as anhydrous ammonia, two seeding rates of oats, and the presence or absence of a herbicide applied to grass pastures before sod-seeding, was conducted at Kyogle, New South Wales in 1964. Plots were sown in mid-autumn and harvested in winter and early spring. Increased applications of nitrogen and the higher seeding rate increased both dry matter yield and total nitrogen content. Application of herbicide significantly increased yield at the low rates of nitrogen but not at the highest rate. Anhydrous ammonia at 120 lb of nitrogen an acre had no effect on the germination of oats seed and provided adequate nitrogen for growth of oats without the need for herbicide application or cultivation of the grass pasture. The results suggest that oats can be successfully sod-seeded into grass dominant pastures by using 120 lb of nitrogen as anhydrous ammonia and four bushels of oats an acre.

Forage Production of Rye, Oats, and Ryegrass as Influenced by Fertilization and Management1

SynopsisOver a 3‐year period, Abruzzi rye produced more for‐age than Southland oats at applied nitrogen rates of 0, 50, 100, 200, and 400 pounds per acre. Domestic ryegrass made little growth at low nitrogen rates, but outyielded oats at the 400‐pound rate. All three species responded to phosphorus and potassium. Forage yields were increased by cutting at bimonthly, rather than monthly, intervals. Application of nitrogen increased the protein content of all species.