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Presidedress Soil Nitrogen Test for No-Tillage Maize at Different Row Spacing

Est. Exp. Agropecuaria INTA Balcarce and Fac. Ciencias Agrarias (U.N.M.P.), Unidad Integrada Balcarce, C.C. 276 (7620) Balcarce, Buenos Aires, Argentina

^* Corresponding author (pbarbieri{at}balcarce.inta.gov.ar).

A presidedress soil nitrate test (PSNT) can be used to evaluate preplant N applications as a complementary method to N budget in maize (Zea mays L.) under different management practices. Narrow rows have shown increased N accumulation and recovery efficiency by maize, and therefore soil NO₃^––N critical concentration (CC) for maximum yield could be lower than in conventional row spacing. An experiment was performed at Balcarce (Argentina) in 1996–1997, 1999–2000, and 2000–2001 to evaluate the PSNT for irrigated no-till (NT) maize with different row spacings (70, 52, and 35 cm) and N rates (0, 90, 140, and 180 kg N ha^–1). Soil samples were collected to a 30-cm and 30- to 60-cm depth when maize was at the six-leaf stage (V6). Grain yield was significantly increased by narrow rows mainly at low N availability. Relative yield was highly associated (r² = 0.73 and 0.68) with soil NO₃^––N concentration (0–30 cm) at V6 for conventional and narrow rows, respectively. Soil NO₃^––N concentration for maximum yield (95%) was greater for conventional row spacing (22 mg kg^–1) compared with narrow rows (17 mg kg^–1). The reliability of the PSNT (r²) did not improve when sampling was done up to a 60-cm depth. These results confirm the hypothesis that the NO₃^––N CC determined for the PSNT is lower for maize crops growing in narrow rows than conventional row spacing. Narrow rows maize is a simple management practice that could contribute to enhancing system sustainability.

Abbreviations: CC, critical concentration • CET, crop evapotranspiration • CT, conventional tillage • ETO, evapotranspiration • NT, no-till • NUE, nitrogen use efficiency • PSNT, presidedress soil nitrate test • RE, recovery efficiency • RY, relative yield

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Received for publication February 22, 2006.