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Denitrification in Maize Under No–Tillage

Effect of Nitrogen Rate and Application Time

Facultad de Ciencias Agrarias (U.N.M.P.)-Estación Experimental Agropecuaria Balcarce (I.N.T.A.), Unidad Integrada Balcarce, C.C. 276, (7620) Balcarce, Buenos Aires, Argentina

View larger version (24K): [in a new window]   Fig. 1. Denitrification N losses in no-tillage irrigated maize as a function of N rates and application times in the 1996–1997 and 1998–1999 growing seasons. 0–N is the control; 70, and 210 is kg N ha-1; P is fertilization at planting; V6 is fertilization at the six-leaf stage; F is flowering; PM is physiological maturity. Asterisks indicate significant effect (P 0.05) of the N rate on denitrification rates log-transformed.

View larger version (26K): [in a new window]   Fig. 2. Soil NO3–N content at 0- to 15-cm depth during 1996–1997 and 1998–1999 growing seasons in no-tillage (NT) irrigated maize, for urea fertilization at maize planting (P) and at the six-leaf stage (V6). 0–N is the control; 70 and 210 is kg N ha-1; F represents flowering; PM is physiological maturity. Asterisks indicates significant effect (P 0.05) of N rate on soil NO3–N concentration.

View larger version (25K): [in a new window]   Fig. 3. Soil water filled pore space (WFPS) and rainfall (continuous bars) plus irrigation (dashed bars) during 1996–1997 growing season in no-tillage maize. P represents urea applied at planting; V6 represents urea applied at the six-leaf stage (V6). 0–N is the control; 70 and 210 is kg N ha-1; F represents flowering.

View larger version (25K): [in a new window]   Fig. 4. Soil water filled pore space (WFPS) and rainfall (continuous bars) plus irrigation (dashed bars) during 1998–1999 growing season in no-tillage maize. P repesents urea applied at planting; V6 represents urea applied at the six-leaf stage (V6). 0–N is the control; 70 and 210 is kg N ha-1; F represents flowering; PM represents physiological maturity.

View larger version (24K): [in a new window]   Fig. 5. The relationship between denitrification rate (DR) and water filled pore space (WFPS) in no-tillage irrigated maize during 1996–1997 and 1998–1999 growing seasons. Full and empty symbols correspond to fertilization at planting (P) and at the six leaf stage V6, respectively. 0–N is the control; 70 and 210 eqauls kg N ha-1.

View larger version (19K): [in a new window]   Fig. 6. The relationship between denitrification rate and water filled pore space (WFPS) for treatments fertilized (TF) at planting with 70 and 210 kg of N ha-1 (empty symbols) and for treatment control (0–N; full symbols).