Slow-release Nitrogen Fertilizer Research Articles

Relative efficiency of urea, nitrification inhibitor treated urea and slow release nitrogen fertilizers for rice (Oryza sativaL)

SUMMARYA field experiment was made on a sandy clay loam soil during the rainy seasons of 1967 and 1968 to study the relative efficiency of urea, N-serve treated urea, AM-fertilizer, IBDU fertilizer and nitrogen-enriched coal for the rice variety IR-8. Nitrogen-enriched coal supplied very little nitrogen to rice. All other materials were superior to urea. Largest yield of rough rice and nitrogen uptake was obtained with IBDU. The yield of rough rice given by AM-fertilizer was equal to that with IBDU in 1968; in that year both AM-fertilizer and N-serve treated urea supplied as much N to the crop as IBDU. Yield of straw showed no significant difference between these three materials in either year. Ammoniacal and nitrate nitrogen in soil at flowering and at harvest of the rice was most in plots receiving IBDU followed by those receiving AM-fertilizer, N-serve treated urea and urea. Mineral nitrogen in plots receiving N-enriched coal was only slightly more than in control plots.

Nitrification inhibitors and slow-release nitrogen fertilizers for rice (Oryza sativa L.)

SummaryPot-culture experiments were made with the rice variety IR-8 on a sandy clay loam soil to study the relative efficiency of urea, urea treated with nitrification inhibitors N-Serve and AM, AM-fertilizer, and slow-release nitrogen fertilizers IBDTJ, oxamide and N-enriched coal. N-enriched coal supplied very little nitrogen to rice and gave no more yield than the control. All other materials were superior to urea. Largest yield of rough rice and nitrogen uptake by rice was obtained with IBDU and AM-fertilizer. Compared with untreated urea IBDU, oxamide, AM-fertilizer and urea treated with N-Serve or AM left larger amounts of mineral-nitrogen in the soil after the harvest. In the case of nitrification inhibitors residual ammoniacal-nitrogen was more at the higher rates of inhibitors.

The influence of nitrification inhibitors and slow release nitrogen materials on transformations of fertilizer nitrogen in soils of fluctuating moisture content

A laboratory study was made of nitrogen transformations in a sandy clay loam given either urea with and without nitrification inhibitors or slow-release nitrogen fertilizers. Moisture conditions were field capacity, continuous flooding, and alternate flooding and drying. Urea nitrogen was mineralized and fairly well conserved in soil either at field capacity or under continous flooding, but was rapidly lost under alternate flooding and drying. Denitrification losses were reduced with nitrification inhibitors. Oxamide, isobutylidene diurea, and sulfur-coated urea were as effective as the inhibitors in reducing losses under alternate flooding and drying.

Soluble and slow-release nitrogen fertilizer effects on grass forage, as influenced by rate and placement

SUMMARYSoluble ammonium nitrate (AN) and urea were compared with slow-release oxamide and sulphur-coated urea (SCU) as N sources for clipped annual ryegrass (Lolium multiflorum) or common bermuda grass (Cynodon dactylon) in four greenhouse experiments. Mixed and surface applications of a wide range of N rates were evaluated for 9 to 14 cuttings of grass forage. Both granular oxamide and SCU exhibited slow-release N properties, especially when surface-applied. Uptake distribution of N with high application rates of AN and urea tended to resemble that with the slow-release sources. Slow-release properties of oxamide and SCU were accentuated at high application rates. Lower N recovery from surface-applied urea than from AN indicated volatilization loss of urea N. Volatilization loss also occurred with oxamide, but low N recovery from oxamide and SCU resulted largely from incomplete dissolution of the granules during the 18- to 34-week experimental periods. Very low N recovery was obtained from urea formaldehyde having an activity index of 42.

Isobutylidene diurea and other nitrogen fertilizers for seedlings and transplants ofPicea sitchensis in two English forest nurseries

Three slow-release nitrogen fertilizers — medium- and coarse-sized granules of IBDU (isobutylidene diurea) and formalized casein — were applied before sowing or transplanting to Sitka sprucePicea sitchensis, and their effects on growth compared with that on plots not given N or given four topdressings of ‘Nitro-Chalk’ (the source of N used in practice). The comparisons were made at two sites: a very sandy podsol and a sandy loam with better nutrient retention. The experiments with seedlings were continued for four years, those with transplants for three, and the same treatments were applied to the same plots each year.