The current increase in the organic agriculture sector has created a new market for fertilisers approved for organic farming. Off-farm N sources for organic farming are scarce considering the restriction on the use of chemical fertilisers. Thus, when some commercial products are allowed for organic agriculture, commercial opportunities became available. In this study we compare the behaviour of Vegethumus (Veg) and Phenix (Phe), which are two manures allowed for organic farming, with several other manures, ammonium nitrate (AN) and control treatments. A three year field trial and a pot experiment were carried out in order to estimate dry matter yield, N uptake, and N nutritional status of the crops, as well as soil N availability by using anion exchange membranes inserted into the soil. Apparent N recoveries in the field trial were 6.3 % and 58.2 % in Veg and AN plots, respectively, after the application of 380 kg N/ha in the previous 5 growing seasons. In the pot experiment the ANR of Veg and Phe were -5.0 % and 13.6 %, respectively, while in AN pots it was 37.1%. The other organic manures used in the pot experiment gave higher apparent N recoveries than Veg and Phe if their C:N ratios or inorganic-N contents were taken into account. This work stresses that the use of manures approved for organic farming must first be carefully considered by farmers, with reference to price and agronomic value.

The aim of the current paper is to study the effect of different amounts of nitrogen applied in bands of corn hybrids on variables related to corn plant growth and its yield components. The experiment was carried out under no-tillage system at Guarapuava, PR, Brazil, throughout the period of October 1 st 2009 to March 20 th 2010. The treatments resulted in the combination of two simple hybrids of corn (P30R50 and AG8025) and six doses of nitrogen applied in bands (0; 75; 150; 225; 300 and 375 kg N ha -1 in urea form). The treatments were 12 arranged in a 2x6 factorial design of randomized blocks in four replications. The corn hybrid AG8025 had a small number of leaves, smaller rows of grains per stalk and insertion height of primary stalk compared to the hybrid P30R50. However, with a greater plant height, higher overall dry phytomass and productivity point out the influence of genetic variability on the crop. Nitrogen doses influenced significantly biological variables, such as plant height at the phenological stages V 9 and R 1 , insertion height of the primary stalk, branch diameter, number of photosynthetically active leaves at R 1 , stalk diameter, one thousand grains weight and productivity. 295 kg de N ha -1 dose provided estimated yield of 13,032.93 kg ha -1. Factors, such as hybrids and N doses, did not affect harvest index, whose average value corresponded to 0.52. Yield was positively correlated to most of the variables in the study, outstanding yield components, such as dry phytomass of grains per stalk and overall phytomass of the aerial part per plant. It is concluded that knowing the effect of N on corn plant physiology makes the characterization of yield possible and helps in the selection of corn plant as a parameter for N management in bands.