42 IPNI Interpretive Summaries
<strong>Americas</strong> <strong>and</strong> <strong>Oceania</strong> <strong>Group</strong> Mexico <strong>and</strong> Central America: Dr. Arm<strong>and</strong>o Tasistro Global Maize Project in Mexico: Celaya, Guanajuato Project Leader: Roberto Paredes, Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP), Colonia Roque Celaya, Guanajuato. E-mail: rparedesm59@prodigy.net.mx, paredes.roberto@inifap.gob.mx Project Cooperator: Benjamin Zamudio The study started in 2009 in Celaya, State of Guanajuato, Mexico, at 1,830 meters above sea level. The treatment design included a combination of two management systems (plant populations) (Farmers’ practice [FP] <strong>and</strong> a higher population [EI]) <strong>and</strong> three N fertilization regimes (0-N, 300 kg N/ha applied two out of three years, <strong>and</strong> 300 kg N/ha applied every year). In 2011, the six treatments were: 1) 120,192 seeds/ha, 0-N; 2) 120,192 seeds/ha, 300 kg N/ha (0 N in 2009; 300 kg N/ha in 2010); 3) 120,192 seeds/ha, 300 kg N/ha (300 kg N/ha applied both in 2009 <strong>and</strong> 2010); 4) 90,580 seeds/ha, 0-N; 5) 2) 90,580 seeds/ha, 300 kg N/ha (0-N in 2009; 300 kg N/ha in 2010); 6) 90,580 seeds/ha, 300 kg N/ha (300 kg N/ha applied both in 2009 <strong>and</strong> 2010). The first three treatments are considered as an intensification of the last three, which represent the traditional farmers’ practice. Yields responded to N, regardless of its application sequence. The application of 300 kg N/ha increased grain yields from an average of 1.9 t/ha to 10.9 t/ha, a reflection of significantly greater Harvest Index, more ears/ha, <strong>and</strong> larger ears with heavier kernels. Partial Factor Productivity <strong>and</strong> Agronomic Efficiency were 36 <strong>and</strong> 30 kg grain/kg N, respectively. No significant differences in grain yield could be detected between the intensive <strong>and</strong> traditional management options, although plant population at harvest differed significantly between them: 91,600 vs. 68,900 plants/ha, respectively. By harvest time, the plant population under both management systems had decreased by 24% on average, which is higher than normal, especially under experimental conditions. Most of that loss (15%) had taken place by the third week after crop planting. IPNI-28 Global Maize Project in Mexico: Toluca, México Project Leader: Benjamín Zamudio, González Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP), Toluca, México. E-mail: zamudio.benjamin@inifap.gob.mx The study was started in 2009 in Toluca, State of México, at an altitude of 2,370 meters above sea level. The objective was to compare the effects of six combinations of plant populations <strong>and</strong> fertilizer applications. Half of the treatments—labeled as intensive management—included high plant populations <strong>and</strong> the application of a complete fertilizer formula (90 kg P 2 O 5 /ha, 90 kg K 2 O/ha, 44 kg MgO/ha, 50 kg S/ha, <strong>and</strong> 3 kg Zn/ha). The other half of the treatments were similar to current farmers’ practices with regards to plant population <strong>and</strong> fertilizer application (30 kg P 2 O 5 /ha <strong>and</strong> 30 kg K 2 O/ha). Three N fertilizer application regimes were combined with the management systems just described: 0-N, 300 kg N/ha applied two out of three years, <strong>and</strong> 300 kg N/ha applied every year with the intensive management, <strong>and</strong> 0-N, 180 kg N/ha applied two out of three years, <strong>and</strong> 180 kg N/ha applied every year, with the farmers’ management. The 2011 season was very bad, with lack of rain at the beginning; followed by flooding, hail storms, <strong>and</strong> a devastating early frost in the first week of September. The yield levels were therefore lower than in the previous years. Yield under intensive management (3,594 kg/ha) was significantly higher than under traditional management (2,699 kg/ha). This result mirrored the differences in plant population at harvest: 80,208 <strong>and</strong> 62,691 plants/ha in the intensive <strong>and</strong> farmers’ management treatments, respectively. Under intensive management, yields with N (3,906 kg/ha) were 31% higher than without N (2,971 kg/ha), whereas no significant effects from N could be detected under the traditional management. Partial Factor Productivity IPNI Interpretive Summaries 43