Abstract
In relay intercropping systems, late-planted crops often grow under the shade of the canopy of early-planted tall crops and then transfer to full sunlight after the harvest of the early-planted crops. In order to know the effects of recovery growth of the late-planted soya bean in maize–soya bean relay intercropping, a field experiment was carried out to observe architectural, morphological, physiological and anatomical traits of soya bean plants related to shade and subsequent removal in intercropping before and after maize harvest, respectively. During shade period, soya bean biomass was severely reduced, and stem elongation was stimulated. Typical features of shade grown leaves were found, such as lower LMA (leaf mass per unit area), thinner thickness, higher chlorophyll content, lower chlorophyll a:b ratio. Whole-plant leaf area analysis found that soya bean increased leaf area ratio by adjusting leaf morphology rather than by dry mass allocation. After maize harvest, leaf area and leaf mass increased rapidly, contributing to compensation growth in intercropped soya bean. Meanwhile, physiological and anatomical traits of leaf went back to similar levels as grown in sole cropping. However, stem morphological traits were irreversible after removal of shade. Finally, no difference on seed weight per plant of soya bean was observed between relay intercropping and sole cropping. Based on these findings, we speculated the recovery growth might be the direct determining factor on pod formation in soya bean, and improvement on the capacity of recovery growth could increase yield of relay intercropped soya bean.
Highlights
IntroductionDuring the coexisting period in INT, light is the most frequently limiting resource if water and nutrient requirements of crops are satisfied (Francis, 1989), and light is frequently the most important factor related to over yielding by crops mixtures that exhibit temporal complementarity and high efficiency (Malézieux et al, 2009)
Fraction of leaf mass of INT was lower than sole cropping (SOL) at the first sampling time during coexisting period, while fraction of leaf mass (fL) of both treatments went to the same levels since the maize harvest (Figure 2(d))
After the harvest of maize, physiological and anatomical traits of leaf, and leaf area and dry mass fraction of whole plant recovered to similar levels as control plants grown in sole cropping
Summary
During the coexisting period in INT, light is the most frequently limiting resource if water and nutrient requirements of crops are satisfied (Francis, 1989), and light is frequently the most important factor related to over yielding by crops mixtures that exhibit temporal complementarity and high efficiency (Malézieux et al, 2009). Most studies only evaluated the yield of component crop in relay intercropping at the final harvests, the mechanisms on recover from shade of late-planted crop at agronomic and physiological levels were still not fully understood. The increase of total yield of intercropping was associated with the increase in intercropped soya bean yield when planted with tall component crops in relay intercropping (Andrade et al, 2012). The period of recovery growth of soya bean after maize harvest lasts around two months, which cannot be neglected on yield formation.
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