Nitrogen Fertilizers in Corn Productivity and Nutritional Foliar Composition.

Nitrogen provides yield increase to corn. Despite of volatilization implications, in Brazil urea is the most used source of nitrogen in agriculture. The experiment was a randomized complete block with four replications in no tillage with 100 kg ha^-1 of N as urea, urea+zeolite (15% m/m), ammonium nitrate, urea coated with boric acid (0.4% B) and copper sulfate (0.14% Cu), mixes of ammonium sulfate (33.3%) + urea (66.7%) and ammonium sulfate (33.3%) + urea coated (66.7%) and a control (without N) in surface application in 2010 under corn residue and in 2011 under soybean residue.

Nutritional foliar composition and height of ear insertion of corn were evaluated during inflorescence. Productivity was determined with 13% of grain humidity and grain quality was determined through mass of 1000 grains and crude protein. Organic nitrogen fraction in soil after harvest (0-20 cm) was analyzed through ISNT (Illinois soil nitron test).

The average productivity through contrast analyses in 2010 obtained superiority of 952.5 kg ha^-1 for treatments with urea compared to control (p<0.01). Among treatments based in urea there were superiority of 815.6 and 644.4  kg ha^-1 for ammonium sulfate + urea coated and urea coated compared to other treatments with urea (p<0.05). In 2011 there was no nitrogen fertilization effect compared to control and also for contrasts among treatments with urea.

In 2010, nitrogen application influenced positively to height of ear insertion compared to control. Effects of high soil fertility influenced by soybean residue and the climatic condition in 2011 resulted in low effects of the nitrogen fertilizers. ISNT detected no effect of nitrogen sources however it detected high organic nitrogen levels ranging of 343 to 419 kg ha^-1.

In conclusion, in no tillage with high fertility soil under appropriate climatic condition showed lower capacity to distinguish different nitrogen sources.