Prospects for improving the productivity of species mixtures in transitions between phases by changing row configuration at sowing were examined in two series of field experiments in rain-fed, semi-arid environments in south-eastern Australia. The first series explored how the choice of cover crop and use of alternate drill row configurations affected establishment and yields of sward components in the transition from a cropping into a pasture phase. Cover-crop species included wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), canola (Brassica napus L.) and lupins (Lupinus augustifolius L.), each sown in mixed or alternate drill rows with lucerne (Medicago sativa L.) and subterranean clover (Trifolium subterraneum L.). The second series of experiments examined the productivity implications when returning from the pasture phase back into cropping following 10 contrasting pastures sown to various combinations of lucerne, subterranean clover or phalaris (Phalaris aquatica L.) sown in mixed, alternate (1:1) or double skip (1:2) row configurations in the absence of cover crops. All experiments were sown on a 0.25-m row spacing. In the transition into the pasture phase, grain yields of cover crops in the mixed drill row treatment were similar to those achieved by crops grown in the absence of pasture species but were reduced by an average of 24% in the alternate drill row configuration. Canola and lupin crop biomass were lower, compared with wheat and barley, leading to increased pasture yields in year 1, highlighting an opportunity for increased use of these species as cover/companion crops in semi-arid environments. Pasture yields beyond year 1 were reduced by ~20% in the alternate drill row treatments compared with where species were sown in mixed drill rows, with greater yield differences under more favourable growing conditions. This response largely reflected yield reductions in lucerne where it was concentrated in fewer drill rows. The alternate drill row configuration increased the abundance of subterranean clover in year 1, but this species remained a minor component of all swards beyond the establishment year. In the transition into the cropping phase, effects on grain quality could only be attributed to row configuration of the previous pasture to the extent that row configuration changed pasture composition. Grain size was smallest and protein concentration highest where previous pastures contained both lucerne and subterranean clover without phalaris. Taken together, there was little advantage in total productivity attributable to spatially separating species in drill rows at sowing.

中文翻译：

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在作物和牧草阶段之间的过渡中播种时空间配置变化的后果

在澳大利亚东南部的雨养半干旱环境中进行了两个系列的田间试验，研究了通过改变播种时的行配置来提高相间过渡中物种混合物生产力的前景。第一个系列探讨了覆盖作物的选择和交替钻排配置的使用如何影响从种植阶段过渡到牧场阶段的草地成分的建立和产量。覆盖作物种类包括小麦 ( Triticum aestivum L.)、大麦 ( Hordeum vulgare L.)、油菜 ( Brassica napus L.) 和羽扇豆 ( Lupinus augustifolius L.)，每种都与苜蓿 ( Medicago sativa ) 混合或交替播种L.) 和地下三叶草 (地下三叶草L.)。第二个系列的实验研究了在 10 个对比不同的牧场播种不同的苜蓿、地下三叶草或蜈蚣（Phalaris水生植物L.) 在没有覆盖作物的情况下以混合、交替 (1:1) 或双跳 (1:2) 行配置播种。所有试验均以 0.25 米的行距播种。在过渡到牧场阶段，混合钻排处理的覆盖作物的谷物产量与在没有牧场物种的情况下种植的作物相似，但在交替钻排配置中平均减少了 24%。与小麦和大麦相比，油菜和羽扇豆作物的生物量较低，导致第一年的牧场产量增加，突出了在半干旱环境中增加使用这些物种作为覆盖/伴生作物的机会。与在混合钻排中播种的物种相比，交替钻排处理中超过 1 年的牧场产量减少了约 20%，在更有利的生长条件下产量差异更大。这种反应在很大程度上反映了卢塞恩的产量下降，该产量集中在较少的钻排中。交替的钻排配置在第 1 年增加了地下三叶草的丰度，但在建立年份之后，该物种仍然是所有草地的一小部分。在过渡到种植阶段，对谷物质量的影响只能归因于先前牧场的行配置，因为行配置改变了牧场组成。在以前的牧场既含有苜蓿又含有无趾草的地下三叶草的地方，谷物尺寸最小，蛋白质浓度最高。总而言之，由于在播种时在钻排中空间分离物种，总生产力几乎没有优势。