Winter cereals grown for grain and for the dual purpose of forage plus grain II. Water use and water-use efficiency

Abstract

Water use of barley ( Hordeum distichon L.) and triticale (× Triticosecale Wittmack) grown for the dual purpose of forage plus grain as an alternative to traditional grain monoculture (control) was assessed at Granada, southern Spain, in two experiments during three cropping years. No significant differences in seasonal evapotranspiration (ET) and soil water depletion at maturity were found between production targets, irrespective of genotype, sowing date and year. A more efficient use of autumn and winter rainfall explained the higher water use observed in 1989/90 in early sown barley as compared to the normal sowing date. There were differences in water-use efficiency (WUE) between seasons in response to clipping: in 1987/88, clipping increased WUE in both experiments relative to the control, while it either reduced it (genotype experiment) or did not affect it (sowing system experiment) in the two following seasons. The response of WUE to clipping was a consequence of similar, differential responses between years observed in dry matter and grain production. Weather-crop interactions caused variable drought and crop water-use patterns among years, which affected the different responses to clipping observed among years. In 1987/88, the crops experienced a prolonged drought period that started around clipping, and increased in severity until anthesis, when spring rains improved growth conditions for some weeks. Forage removal decreased water use and reduced plant water deficit, therefore allowing for enhanced growth and increased water use around anthesis. Thus, clipped cereals had higher grain numbers, dry matter and grain yield than the control at harvest. However, the water-use partitioning observed in the clipping-anthesis period of 1987/88 did not occur in following two seasons. This was possibly due to higher soil evaporation losses after forage removal for clipped cereals in 1988/89, and higher water availability in the clipping-anthesis period in 1989/90. Thus, clipping, by reducing the photosynthetic surface after forage removal, yielded less biomass and grain, and resulted in lower WUE, relative to the control. Winter forage production was associated to ET in 1987/88 and 1989/90, and to WUE in 1988/89 and 1989/90, during the crop phases prior to clipping. However, the increases in ET did not imply lower water availability for subsequent crop phases, as it was the result of more efficient use of autumn and winter rainfall.