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Abstract. Biomass sorghum ( (L.) Moench) is widely recognized for its high biomass yield potential, high efficiency in converting solar energy into biomass, and high efficiency in water use for biofuel production. Therefore, it could be a sustainable alternative to traditional food/feed crops in south Texas. The objectives of this investigation were to: (1) quantify the growth response and dry biomass productivity of a forage sorghum hybrid (Pioneer 877F) and two high-biomass sorghum hybrids (Blade ES 5140 and Blade ES 5200) in south Texas, (2) determine the radiation use efficiency (RUE) and water use efficiency (WUE) of the sorghum hybrids over two years, and (3) identify variations in WUE and water used among the hybrids. The experiments were conducted at the Texas A&M AgriLife Research Center at Weslaco, Texas, during the 2015 and 2016 growing seasons. There were significant differences among hybrids during the two years in dry biomass, RUE, and WUE. The highest productivities and efficiencies were observed in the biomass hybrids. Blade ES 5200 produced an average dry biomass of 32.8 Mg ha-1 with a leaf area index (LAI) of 6.0 m2 m-2, RUE of 4.92 g MJ-1, and WUE of 6.98 kg m-3. In contrast to the biomass hybrids, the forage hybrid produced the lowest yields. The average dry biomass observed was 20.9 Mg ha-1 with an LAI of 2.6 m2 m-2, RUE of 3.52 g MJ-1, and WUE of 4.28 kg m-3. Our results show that biomass sorghum hybrids can produce up to 66% more biomass than forage hybrids, and they have potential for producing as much as 33 Mg ha-1 with 530 mm of water using drip irrigation in south Texas. Keywords: Biomass sorghum, Crop growth rate, Radiation use efficiency, Water use efficiency.

Abstract. Energy sorghum is one of the most attractive alternatives for producing energy in many regions of the world because of the high biomass productivity obtained in a short period. However, it faces many challenges, particularly where water resources are limited. Crop simulation models are suitable decision support tools for the assessment of crop water use and biomass production under different spatial and climatic conditions. Calibration of simulation models to local conditions is a necessary procedure to improve model reliability. The objective of this study was to calibrate and evaluate the Environmental Policy Integrated Climate (EPIC) model for the production of energy sorghum under different irrigation levels. The model was then used to simulate crop biomass productivity and crop water use to identify appropriate irrigation strategies. This study was conducted at the Texas A&M AgriLife Research Center in Weslaco, Texas. Simulations were performed to determine the total dry biomass, crop water use, the relationship between crop productivity and crop evapotranspiration (ETc), and water use efficiency (WUE). Simulated ETc agreed well with estimates from a weather station, except for a few simulation events. The statistical parameters derived from measured versus simulated dry biomass in the calibrated model, which indicated that the model performed well, were R2 = 0.99 and PBIAS = -5.35%. The calibrated model showed great potential for simulating the total dry biomass. At full irrigation, the difference between measured and simulated total dry biomass was 4.3% in 2013 and 3.0% in 2015. This study showed that energy sorghum requires approximately 600 mm of water to obtain 23 Mg ha-1 of total dry biomass. It also demonstrated that the EPIC model could be used for assessment of crop water use and total biomass under limited irrigation levels, especially in semi-arid regions. Keywords: Crop model, Dry biomass, Energy sorghum, EPIC model, Irrigation, Model calibration, Water use efficiency.

ResumenEl documento tiene por objetivo abordar el estudio de la eficiencia del sector agropecuario mexicano en apec, considerando la presencia de bad outputs, durante el período 1980-2015. Lo anterior es importante debido a que el establecimiento de mecanismos que mejoren el uso eficiente de los recursos para generar un mayor valor agregado, y a la par reduzcan las emisiones de CO2eq en el sector es imprescindible para que el país aspire a mayores niveles de desarrollo. Para medir la eficiencia se hizo uso del Análisis de la Envolvente AbstractThis paper aims to study the efficiency of the Mexican agricultural sector in the context of apec, taking into account the "bad outouts" that occurred during the period 1980-2015. The establishment of mechanisms that improve the efficient use of resources to generate greater added value and at the same time reduce CO2eq emissions in the sector, are essential so that Mexico can aspire to higher levels of development. In order to measure efficiency, Data Envelopment Analysis, was used, and in order to assess the evolution of productivity the Malmquist-Luenberger index was calculated. The results show that during the entire length of the period studied the Mexican agricultural sector was more efficient than order APEC contries. However, its productivity worsened due to the need for technological improvements that allow a displacement of the production possibilities frontier.

Accurate estimation of radiation use efficiency (RUE) at variable timed sowing dates will enhance the prediction of plant dry matter accumulation. The objectives of this study were to (1) determine the impact of three sowing dates on the productivity, performance, and economic feasibility of three biomass sorghum hybrids and (2) evaluate the variability of RUE in the production of biomass sorghum under the effects of variable timed sowing dates. Over a two-year experiment, biomass sorghum hybrids were grown and monitored at different sowing seasons under optimal growth conditions. Average dry biomass (DB) productivity at harvest ranged from 22.71 to 32.77 Mg ha−1. Higher leaf area index (LAI) values (>4.0) represented an intercept of over 95% of incident photosynthetically active radiation (PAR). RUE obtained from the slope of the linear relationship between DB produced and accumulated intercepted photosynthetically active radiation (IPAR) ranged from 2.92 to 4.157 g MJ−1 across growing seasons. Higher RUE values were observed for the energy hybrids in the early and mid-season. They converted IPAR efficiently into DB. Lastly, the economic feasibility of each sorghum hybrid and sowing date was evaluated in terms of their expected net returns. Economic results suggest that the sorghum hybrids considered could be a viable source of biomass season long, with net returns ranging from USD 560.55 ha−1 to USD 1255.06 ha−1.