Uma das práticas desafiadoras de manejo é aumentar a produção de arroz utilizando menos água. O experimento foi realizado nas safras de 2010/11 e 2011/12 na área experimental da Universidade Federal de Santa Maria, Rio Grande do Sul. O objetivo foi avaliar o rendimento de grãos e a eficiência do uso de água na semeadura no início e final da época recomendada. Os tratamentos foram as épocas de semeadura (01/10/10 e 01/12/10) safra 2010/11, e (27/09/11 e 07/12/11) safra 2011/12, com cinco repetições, e a cultivar utilizada foi a 'IRGA 424'. Não houve diferença no volume de água aplicado entre as épocas de semeadura, com volume médio de 5757 e 8420m³ ha-1, respectivamente, para safra 2010/11 e 2011/12. A época de semeadura afetou o rendimento de grãos, com rendimento de 13 e 24% a mais nas semeaduras do início da época (01/10/10 e 27/09/11), comparado às semeaduras do final da época (01/12/10 e 07/12/11), respectivamente. A semeadura realizada no início da época recomendada (início de outubro) proporciona maior rendimento de grãos e maior eficiência no uso de água.<br>One of the challenging management practices is to increase rice production using less water. The study was conducted during the harvest of 2010/11 and 2011/12 in the experimental field of Universidade Federal de Santa Maria, Rio Grande do Sul State, Brazil. The objective was to evaluate the yield and water use efficiency at sowing at beginning and end of the recommended time. Treatments were at planting dates (10/01/10 and 12/01/10) 2010/11 harvest, and (9/27/11 and 12/07/11) 2011/12 harvest, with five replicates, the cultivar used was the 'IRGA 424'. There was no difference in the amount of applied water between sowing times, with an average of 5757 and 8420m³ ha-1, respectively for season 2010/11 and 2011/12. The sowing date affected grain yield, with yields of 13 and 24% more in the beginning of the sowing season (10/01/10 and 9/27/11) compared to the end of the sowing date (12/01/10 and 12/07/11), respectively. Sowing early in the recommended period (early October) provides greater yield and more water use efficiency.

Uma das práticas desafiadoras de manejo é aumentar a produção de arroz utilizando menos água. O experimento foi realizado nas safras de 2010/11 e 2011/12 na área experimental da Universidade Federal de Santa Maria, Rio Grande do Sul. O objetivo foi avaliar o rendimento de grãos e a eficiência do uso de água na semeadura no início e final da época recomendada. Os tratamentos foram as épocas de semeadura (01/10/10 e 01/12/10) safra 2010/11, e (27/09/11 e 07/12/11) safra 2011/12, com cinco repetições, e a cultivar utilizada foi a 'IRGA 424'. Não houve diferença no volume de água aplicado entre as épocas de semeadura, com volume médio de 5757 e 8420m³ ha-1, respectivamente, para safra 2010/11 e 2011/12. A época de semeadura afetou o rendimento de grãos, com rendimento de 13 e 24% a mais nas semeaduras do início da época (01/10/10 e 27/09/11), comparado às semeaduras do final da época (01/12/10 e 07/12/11), respectivamente. A semeadura realizada no início da época recomendada (início de outubro) proporciona maior rendimento de grãos e maior eficiência no uso de água. | One of the challenging management practices is to increase rice production using less water. The study was conducted during the harvest of 2010/11 and 2011/12 in the experimental field of Universidade Federal de Santa Maria, Rio Grande do Sul State, Brazil. The objective was to evaluate the yield and water use efficiency at sowing at beginning and end of the recommended time. Treatments were at planting dates (10/01/10 and 12/01/10) 2010/11 harvest, and (9/27/11 and 12/07/11) 2011/12 harvest, with five replicates, the cultivar used was the 'IRGA 424'. There was no difference in the amount of applied water between sowing times, with an average of 5757 and 8420m³ ha-1, respectively for season 2010/11 and 2011/12. The sowing date affected grain yield, with yields of 13 and 24% more in the beginning of the sowing season (10/01/10 and 9/27/11) compared to the end of the sowing date (12/01/10 and 12/07/11), respectively. Sowing early in the recommended period (early October) provides greater yield and more water use efficiency.

Conocer el rendimiento potencial (RP) es necesario para establecer la brecha productiva con respecto al rendimiento que obtiene el productor. Este trabajo utilizó diferentes modelos para estimar RP en papa (Solanum tuberosum L.) de ciclo tardío en Córdoba, Argentina, comparando dos métodos basados en: a) la eficiencia del uso de la radiación (RPe) y b) la eficiencia o productividad del agua, normalizada con el déficit de presión de vapor (RPwD) y con la evapotranspiración de referencia (RPwETo). El RPe para cuatro fechas de plantación entre 2007 y 2012 resultó muy variable (CV=17,7%), con un promedio de 9,7 Mg ha-1 de peso seco (PS), disminuyendo entre 1 y 1,4% del RP por día de atraso de la plantación. El RPwD promedio fue significativamente (P < 0,001) menor (8,4 Mg PS ha-1), con una variabilidad similar entre años y épocas de plantación (CV = 17,3%), y la misma tendencia a disminuir con el retraso de la plantación. El RPwETo fue ligeramente menor (9,3 Mg PS ha-1) al RPe, diferencia que no fue significativa (P > 0,05), y sus resultados fueron menos variables (CV = 9,7%). | Knowing the potential yield (RP) of potato crop (Solanum tuberosum L.) is needed to establish the productivity gap compared to yields obtained by producers. This article uses different models to estimate the RP for late potato growing season in Córdoba, Argentina, comparing two methods based on: a) radiation use efficiency (RPe) and b) efficiency or productivity of water (w), which was normalized according to vapor pressure deficit (RPwD) and the reference crop evapotranspiration (RPwETo). The RPe for four planting dates from 2007 to 2012 was highly variable (CV = 17.7%), with a mean value of 9.7 Mg ha-1 of dry weight (PS), showing a gradual trend to decrease with the delay of planting, with a rate between 1 and 1.4% of RP per day of delay. The average RPwD was significantly (P < 0.001) lower (8.4 Mg PS ha-1), with similar variability between years and planting dates (CV = 17.3%), and the same trend to decrease was observed as planting was delayed. The RPwETo tended to be only slightly lower (9.3 Mg PS ha-1) than those obtained with Rpe. This difference was not significant (P > 0.05), and its estimates were less variable (CV = 9.7%).