The positive effect of placing N (especially NH+4‐N) with P on crop growth has been demonstrated many times in short‐term greenhouse studies. Under field conditions, however, the effect has not been well defined. The present objective was to evaluate N and P placement methods on the P nutrition and final grain yield of wheat (Triticum aestivum L.) grown in the field and greenhouse. Anhydrous ammonia (NH3), urea‐ammonium nitrate solution (UAN), and sodium nitrate (SN) were N sources while liquid ammonium polyphosphate (APP) was the P source. Methods of N‐P application included: knife N‐knife P (‘dual knife’), knife N‐hroadcast P, broadcast N‐knife P, and broadcast N‐broadcast P. Two nitrification inhibitors were included in some studies. In the greenhouse, APP was labelled with 33P orthophosphate and 32P pyrophosphate to examine P uptake of its ortho‐ and polyphosphate fractions with different N‐P‐K application methods each with either a NH+4‐N or NO‐3‐N source.Dual knife N‐P applications gave higher leaf P concentrations and grain yields than other N‐P application methods in many of the field studies when ammoniacal N sources were used. Sodium nitrate dual knife applications were not as effective as dual knife applications of UAN or ammonia. The inclusion of the nitrification inhibitor nitrapyrin to dual knife treatments increased grain yield and/or leaf tissue P level in two 1978 studies, but had no effect in 1979. In the greenhouse the highest leaf P levels resulted from the banded NH3‐APP application. The banded SN‐APP application gave the second highest P uptake. This study also demonstrated that the N and APP need to be placed together, not separately in the soil. The amounts of the initial ortho‐ and polyphosphate portions of the APP absorbed by the plants seemed to be a function of fertilizer P demand and not related to fertilizer N in the same band. Including KCl in a band of APP did not affect leaf tissue P concentrations.
A field experiment using ammonium sulfate tagged with 7.65 A% 15N was conducted to assess how rates and times fertilizer is applied influence the fate of N applied to winter wheat (Triticum aestivum L.). Bottomless metal boxes were pressed 142 cm into the soil to confine the tagged fertilizer. Treatments, replicated four times, consisted of two rates (50 and 100 kg N/ha) and two application times (fall and spring). Fertilizer N used by the crop and that remaining in the upper 180‐cm of the soil after harvest were measured. Amounts of ammonium‐N and nitrate‐N from the fertilizer in the 0 to 10‐cm layer also were determined.The N balance indicated 9.7 – 10.3 kg N/ha were unaccounted for at the 50‐kg N rate and 19.7 · 23.4 kg, at the 100‐kg rate. Losses did not differ significantly between application times. With 100 kg/ha the crop removed significantly more fertilizer N, and significantly less remained in the soil with spring than with fall applications. The crop used similar amounts of total N in each case, but with the spring applications more fertilizer N but less soil N was taken up. Fertilizer applications caused no priming effect on mineralization of indigenous soil N. Most of the fertilizer remaining in the soil was in the 0 to 10‐cm layer, with no evidence of N moving deeper than 50 cm, so losses were from gaseous loss rather than leaching.Most of the fertilizer N in the 0 to 10‐cm layer of soil after harvest was immobilized, with only 9.6 – 11.5% remaining in inorganic forms. Immobilization was the principal reason for differences in spring and fall applications and for limited leaching. The percentages of NH4+‐N and NO3‐‐N, which originated from the fertilizer were 4 – 8 times the percentages of total N from the fertilizer, so more fertilizer N was in inorganic forms than was the case with indigenous soil N. Since there was a direct relationship between amounts of NO3‐‐N in the surface soil from fertilizer and amounts of N unaccounted for, it was concluded that gaseous losses resulted from denitrification processes.
Dismutation of Mercurous Dimer in Dilute Solutions 1837 of acidity.10 It is reasonable to expect that the true Ho values lie somewhere in between these limits, which would bring the experimental points into fair agreement with curve A. It would appear, then, that in the presence of a constant excess of H202 and HüSO*, the position of equilibrium is governed solely by acidity.The behavior of the peroxy-niobium system is best exemplified by comparison to the chromatedichromate system. The similarity of ( 9) to (1)
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