Subtropical pastures are an important alternative to increase forage yields to fulfil cattle nutritional requirements. Despite the increasing expansion of these pastures in the semiarid subtropical region of Argentina, there is very little information about their responses to grazing management. The aim of this study was to evaluate the effect of different defoliation regimes on morphogenesis, sward structure and leaf area index of one of the most expanded forage species in this region, Chloris gayana Kunth. A combination of two defoliation frequencies (300 and 500 GDD) and two defoliation intensities (1 and 3 green stubble leaves) was compared by a controlled experiment that comprised 1,500 GDD. Defoliation frequency significantly affected leaf elongation rate (LER) and leaf area index (LAI). Under the high defoliation frequency, LER and LAI resulted almost half than under low defoliation frequency (0.34 ± 0.08 vs. 0.67 ± 0.08 mm·tiller⁻¹·GDD⁻¹; 8.31 ± 2.27 m²/m² vs. 13.27 ± 1.59 m²/m², at 300 or 500 GDD respectively), regardless of the intensity. Defoliation frequency or intensity did not affect leaf appearance rate, leaf lifespan, leaf size, number of green leaves per tiller nor tiller density at the end of the experiment. We conclude that to maintain high LER and LAI in Chloris gayana Kunth cv. Épica INTA‐Pemán pastures, defoliation frequency could be of 500 GDD. Since leaf lifespan was 415 ± 110 GDD, under this defoliation frequency, a maximum accumulation of green leaf tissues with very little dead tissues may be achieved.

中文翻译：

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Chloris gayana Kunth在不同的落叶体制下。形态发生，草皮结构和叶面积指数

亚热带牧场是增加牧草产量以满足牛营养需求的重要替代方法。尽管这些草场在阿根廷的半干旱亚热带地区不断扩大，但关于它们对放牧管理的反应的信息很少。这项研究的目的是评估不同的落叶方式对该地区最大的饲草种类之一Chloris gayana的形态发生，草皮结构和叶面积指数的影响。昆斯。通过包含1,500 GDD的对照实验，比较了两种脱叶频率（300和500 GDD）和两种脱叶强度（1和3绿茬叶）的组合。落叶频率显着影响叶片伸长率（LER）和叶面积指数（LAI）。在高脱叶频率下，LER和LAI几乎是低脱叶频率下的一半（0.34±0.08对0.67±0.08 mm·分iller ^-1 ·GDD ^-1； 8.31±2.27 m ² / m ²对13.27±1.59 m ² /米²，分别为300或500 GDD），而与强度无关。在实验结束时，落叶的频率或强度不会影响叶片的出现率，叶片的寿命，叶片的大小，每个分er的绿叶数或分till密度。我们得出结论，要保持Chloris gayana Kunth cv的较高LER和LAI 。ÉpicaINTA-Pemán牧场，落叶频率可能为500 GDD。由于叶片的寿命为415±110 GDD，因此在该脱叶频率下，可以获得绿色的叶片组织最大积累，几乎没有死组织。