Análisis comparativo de diferencias de rendimiento entre sorgo y maíz
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Date
2022
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Facultad de Ciencias Agrarias. Universidad Nacional de Rosario
Abstract
Los cultivos de maíz y sorgo tienen una amplia difusión en Argentina, pero
históricamente el sorgo ha ocupado un puesto muy distinto al actual. Esta tesis busca
comparar ambos cultivos usando diferentes aproximaciones: datos públicos de rendimiento a
nivel de productor, datos experimentales de rendimiento con ambos cultivos creciendo en
simultaneo y bajo un mismo manejo, y datos experimentales comparando la biomasa
remanente de ambos cultivos. Estudios previos mostraron que la ganancia genética en
rendimiento ha sido muy superior en maíz comparada con sorgo, aumentando su rendimiento
potencial y estabilidad frente a condiciones de stress hídrico y de nutrientes. La hipótesis de
trabajo es que el rendimiento de maíz es actualmente superior al de sorgo en ambientes de
más de 4000 kg ha-1
, y que la ventaja del cultivo de sorgo reside principalmente en la cantidad
y calidad del rastrojo remanente.
Ambos cultivos evidenciaron rendimientos similares en la década de 1970, pero la
evolución del rendimiento a nivel de productor fue muy distinta entre cultivos a partir de esa
fecha. El rendimiento de maíz a nivel nacional se incrementó a una tasa promedio de 110 kg
ha-1 año-1
, mientras que la tasa de incremento del rendimiento de sorgo fue considerablemente
menor, promediando 62 kg ha-1 año-1
. La diferencia en favor del maíz fue más evidente a partir
de mediados de la década de 1990, con la introducción de materiales modificados
genéticamente. El incremento del rendimiento en favor del maíz fue acompañado de mayor
estabilidad (0,18 y 0,15% año-1 para maíz y sorgo, respectivamente) y mayor superficie
sembrada en todas las zonas productivas de Argentina (3,8 Mha en 2016), y va de la mano
de una contrastante inversión de tecnología (principalmente mejoramiento genético y
biotecnología) entre cultivos. Estos resultados concuerdan con aquellos obtenidos al
comparar ambos cultivos en las mismas condiciones ambientales. La diferencia de
rendimiento (maíz menos sorgo) osciló entre -0,3 y 4,8 Mg ha-1
, y fue significativamente mayor
en maíz excepto en uno de los ambientes explorados. La diferencia a favor del cultivo de maíz
aumentó a medida que mejoraron las condiciones ambientales, evidenciando el mayor
potencial de rendimiento de maíz. El rendimiento de indiferencia por debajo del cual el sorgo
superó al maíz fue de solo ~1800 kg ha-1
, lo que concuerda con la mayor tolerancia a estrés
de los híbridos comerciales actuales de maíz. El sorgo presentó valores de índice de cosecha
bajos y poco estables cuando se lo comparó con maíz. Por último, la biomasa remanente fue
mayor en sorgo que en maíz (12,8 y 10,1 t ha-1
, respectivamente), pero más lábil, resultado
que presenta nuevos interrogantes por sus implicancias prácticas. La principal conclusión de
esta tesis es que es necesario generar mayor inversión en genética y tecnología en el cultivo
de sorgo, aunque el mismo tiene que ser acompañado con otros mecanismos que motiven su
implantación. El mejoramiento debería focalizarse en aumentar la partición reproductiva en el
cultivo de sorgo, y la difusión del cultivo debería concentrarse en los ambientes más
restrictivos y frágiles ambientalmente, donde todavía es posible una ventaja en rendimiento y
donde la biomasa remanente del sorgo respecto al maíz le genera un beneficio adicional.
Maize and sorghum crops are widely spread in Argentina, but historically sorghum has occupied a different place than it does today. This thesis seeks to compare both crops using different approaches: public yield data at farmer level, experimental yield data with both crops growing simultaneously and under the same agronomic management, and experimental data comparing the stoverof both crops. It is known that the genetic gain in yield has been much higher in maize compared to sorghum, together with an increase in yield potential and stress tolerance. The main tested hypothesis is that corn yield is currently higher than the sorghum one across environments that exceed 4000 kg ha-1 , and that the sorghum crop advantage relies mainly in the quantity and quality of the stover biomass left in the field after harvest. Both crops showed similar yields in the 1970s, but the yield trend at farmer fields was very different between crops after that. Nationwide maize yield increased at an average rate of 110 kg ha-1 yr-1 , while the sorghum yield increase rate was considerably lower, averaging 62 kg ha-1 yr-1 . The yield difference in favor of maize was more evident starting mid-1990s, with the introduction of genetically modified hybrids. The yield increase in favor of maize was accompanied by greater yield stability (0,18 y 0,15% year-1 for maize y sorghum, respectively), and a larger harvested area in all the productive regions of Argentina (3,8 Mha during 2016), and agrees with a different technology investment that is evident when comparting crops (mainly in genetics and biotechnology improvements). These results agree with those reported when comparing both crops under the same environmental conditions. The yield difference (maize minus sorghum) ranged from -0.3 to 4.8 Mg ha-1, and was significantly higher in maize except in one of the explored environments. The yield difference in favor of maize when comparted to sorghum increased as environmental conditions improve, agreeing with the evident higher maize yield potential. The cut-off yield below which sorghum outperforms maize was only ~1800 kg ha-1 , consistent with the higher stress tolerance of current commercial maize hybrids. Finally, the crop residue left in the field after harvest was higher in sorghum than maize (12,8 and 10,1 t ha-1 , respectively), but more labile, which raises additional questions due to its practical implications. The main conclusion of this thesis is a greater investment in genetics and technology in the cultivation of sorghum is needed, although it must be accompanied by other mechanisms to motivate its implementation. Breeding must focus in increasing the reproductive partition, since sorghum showed significantly lower and more variable harvest index values when compared with maize. Sorghum crop cultivation should focus in the more restrictive and environmentally fragile environments, where a yield advantage is still possible, and the higher residue can provide a positive sustainable aspect with respect to maize
Maize and sorghum crops are widely spread in Argentina, but historically sorghum has occupied a different place than it does today. This thesis seeks to compare both crops using different approaches: public yield data at farmer level, experimental yield data with both crops growing simultaneously and under the same agronomic management, and experimental data comparing the stoverof both crops. It is known that the genetic gain in yield has been much higher in maize compared to sorghum, together with an increase in yield potential and stress tolerance. The main tested hypothesis is that corn yield is currently higher than the sorghum one across environments that exceed 4000 kg ha-1 , and that the sorghum crop advantage relies mainly in the quantity and quality of the stover biomass left in the field after harvest. Both crops showed similar yields in the 1970s, but the yield trend at farmer fields was very different between crops after that. Nationwide maize yield increased at an average rate of 110 kg ha-1 yr-1 , while the sorghum yield increase rate was considerably lower, averaging 62 kg ha-1 yr-1 . The yield difference in favor of maize was more evident starting mid-1990s, with the introduction of genetically modified hybrids. The yield increase in favor of maize was accompanied by greater yield stability (0,18 y 0,15% year-1 for maize y sorghum, respectively), and a larger harvested area in all the productive regions of Argentina (3,8 Mha during 2016), and agrees with a different technology investment that is evident when comparting crops (mainly in genetics and biotechnology improvements). These results agree with those reported when comparing both crops under the same environmental conditions. The yield difference (maize minus sorghum) ranged from -0.3 to 4.8 Mg ha-1, and was significantly higher in maize except in one of the explored environments. The yield difference in favor of maize when comparted to sorghum increased as environmental conditions improve, agreeing with the evident higher maize yield potential. The cut-off yield below which sorghum outperforms maize was only ~1800 kg ha-1 , consistent with the higher stress tolerance of current commercial maize hybrids. Finally, the crop residue left in the field after harvest was higher in sorghum than maize (12,8 and 10,1 t ha-1 , respectively), but more labile, which raises additional questions due to its practical implications. The main conclusion of this thesis is a greater investment in genetics and technology in the cultivation of sorghum is needed, although it must be accompanied by other mechanisms to motivate its implementation. Breeding must focus in increasing the reproductive partition, since sorghum showed significantly lower and more variable harvest index values when compared with maize. Sorghum crop cultivation should focus in the more restrictive and environmentally fragile environments, where a yield advantage is still possible, and the higher residue can provide a positive sustainable aspect with respect to maize
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Keywords
Sorgo, Maíz, Rendimiento de cultivos, Biomasa remanente, Argentina