Bell Lindsay W, Kirkegaard John A, Tian Lihua, Morris Sally, Lawrence John
CSIRO Agriculture and Food, Toowoomba, QLD, Australia.
CSIRO Agriculture and Food, Canberra, ACT, Australia.
Front Plant Sci. 2020 Jun 5;11:607. doi: 10.3389/fpls.2020.00607. eCollection 2020.
Dual-purpose crops are grazed during their vegetative phase and allowed to regrow to produce grain. Grazing slow-developing winter cereals (wheat, barley, and triticale) is common, but there is also potential to graze faster-developing spring cereals used in regions with shorter-growing seasons. Defoliation in faster-developing genotypes has risks of larger yield penalties, however, little is known about genotypic characteristics that may improve recovery after grazing. Four experiments examined 7 spring wheat and 2 barley cultivars with differing physiological attributes (phenological development rate, putative capacity to accumulate soluble carbohydrates, and tillering capacity) that may influence the capacity of spring wheat to recover after defoliation. Defoliated and undefoliated crops were compared to assess physiological differences between cultivars including recovery of biomass, leaf area and radiation interception at anthesis, and subsequent crop grain yield and yield components. All genotypes had similar responses to defoliation treatments indicating that the physiological attributes studied played little part in mitigating yield penalties after defoliation. Despite some differences in yield components amongst cultivars, defoliation did not adversely affect cultivars with different yield component combinations under non-water limited conditions. Later and intense defoliation (around GS30/31) resulted in large yield penalties (40%) which reduced both grain number and kernel mass. However, earlier defoliation (before GS28) induced small or insignificant yield penalties. Defoliation often reduced canopy radiation interception and crop biomass at anthesis but this rarely translated into large yield penalties. These studies further demonstrate that shorter season spring cereals can provide valuable forage (up to 1.2 t DM/ha) for grazing during early vegetative growth without inducing large yield penalties. This study suggests that beyond appropriate phenology, there were no other specific characteristics of cultivars that improved the recovery after grazing. Hence farmers don't need specific dual-purpose cultivars and can still focus on those that optimize grain yield potential for a particular environment and sowing date. The timing and intensity of defoliation appear to be larger drivers of yield recovery in spring cereals and better understanding of these relationships are needed to provide grazing management guidelines that mitigate risk of yield penalties in dual-purpose cereal crops.
两用作物在营养生长阶段进行放牧，然后让其重新生长以生产谷物。放牧生长缓慢的冬季谷物（小麦、大麦和小黑麦）很常见，但在生长季节较短的地区种植的生长较快的春季谷物也有放牧的潜力。然而，对生长较快的基因型进行去叶处理会有更大的产量损失风险，不过，对于可能改善放牧后恢复能力的基因型特征，人们了解甚少。四项实验研究了7个春小麦品种和2个大麦品种，这些品种具有不同的生理特性（物候发育速率、假定的可溶性碳水化合物积累能力和分蘖能力），这些特性可能会影响春小麦去叶后的恢复能力。对去叶和未去叶的作物进行比较，以评估品种之间的生理差异，包括生物量恢复、开花期叶面积和辐射截获量，以及随后的作物籽粒产量和产量构成因素。所有基因型对去叶处理的反应相似，这表明所研究的生理特性在减轻去叶后的产量损失方面作用不大。尽管不同品种在产量构成因素上存在一些差异，但在非水分限制条件下，去叶并没有对具有不同产量构成因素组合的品种产生不利影响。后期和重度去叶（在生长阶段30/31左右）导致大幅减产（40%），这降低了粒数和粒重。然而，早期去叶（在生长阶段28之前）导致的产量损失较小或不显著。去叶通常会减少开花期冠层的辐射截获量和作物生物量，但这很少转化为大幅减产。这些研究进一步表明，短季春谷物在营养生长早期可以提供有价值的牧草（高达1.2吨干物质/公顷）用于放牧，而不会导致大幅减产。这项研究表明，除了合适的物候期外，没有其他特定的品种特性能够改善放牧后的恢复能力。因此，农民不需要特定的两用品种，仍然可以专注于那些针对特定环境和播种日期优化谷物产量潜力的品种。去叶的时间和强度似乎是春谷物产量恢复的更大驱动因素，需要更好地理解这些关系，以提供放牧管理指南，降低两用谷物作物产量损失的风险。
