Evaluation of a chlorophyll meter on the assessment of foliar nitrogen in corn

Rafael Novoa S.-A.1 y Nicolás Villagrán A.1

In order to evaluate the use of a chlorophyll meter (SPAD 502), as a tool to estimate the N content of corn (Zea mays) leaves, a field experiment of corn hybrid ‘INIA 160’ was sown at National Agricultural Research Institute (INIA), La Platina Experimental Station, Santiago, Chile. Four nitrogen treatments (0, 100, 200, 400 kg N ha-1) using urea were applied in a completely randomized block design with four replicates. Half of the N was applied at sowing and half at the 6-7 leaf growth stage. The most recently mature leaves were sampled for each treatment. The chlorophyll levels of leaves were measured with the SPAD. Ten measurements were made per leaf: 5 on each side of the central vein for 3 plants per treatment. These same leaves were taken to the lab for N chemical analysis. Readings were taken at two stages, when the corn had 5-6 leaves and a few days after full tassel. According to the results, the SPAD chlorophyll meter readings and foliar N percentage content were highly correlated. At the first and second reading dates, r2 was 0.88 and 0.81, respectively. In this case at the six-leaf stage, SPAD values of less than 35.3, equivalent to 1.84% N in the leaves, would indicate that it is necessary to apply N.

Keywords: corn, foliar nitrogen, nitrogen use, SPAD 502.
1 Instituto de Investigaciones Agropecuarias, Centro Regional de Investigación La Platina, Casilla 439 –3, Santiago, Chile. E-mail: rnovoa@inia.cl; nicovillagran@usa.net