Background Intercropping is assumed to increase food production while reducing fertilizer needs and environmental impacts of crop production. Aims We aimed to (1) investigate the effects of intercropping on yields and nutrient uptake of maize, and (2) determine the relative contributions of above‐ and belowground interspecific interactions (RCabove/below) to these effects. Methods We conducted a 2‐year, small‐scale field experiment with maize grown either in monocropping or intercropped with faba bean, soy, blue lupin, or white mustard as companion crop. We included a treatment in which interspecific root interactions were restricted due to barriers in the soil. Maize and companion crops were analyzed for yields, and maize additionally for nutrient uptake. Maize partial land equivalent ratios (pLER), partial nitrogen and phosphorus equivalent ratios (pNER, pPER), and RCabove/below were calculated. Results Intercropping resulted in a similar productivity of maize as in monocropping on an area basis. Maize pLER, pNER, and pPER were larger than 1.0 in several species combinations, indicating a positive effect of intercropping on maize yields and N and P uptake. Interspecific root interactions accounted for 62–85% of the maize yield increase in legume/maize intercropping, but for only 22% in mustard/maize intercropping. Conclusion Our results indicate that intercropping is beneficial for crop production since it increases maize yields and N and P uptake of maize plants, and it also provides yields of a companion crop. A substantial part of these positive effects can be attributed to interspecific root interactions.
The aim of the study was to examine interspecific plant interactions that contribute to plant nitrogen (N) and phosphorus (P) acquisition and are likely the reason for overyielding in intercropping. We conducted a field and a rhizobox experiment with the same soil. Maize (Zea mays L.) was grown alone or intercropped with the companions faba bean (Vicia faba L.), soy (Glycine max (L.) Merr.), blue lupin (Lupinus angustifolius L.), or white mustard (Sinapis alba L.). We determined the isotopic N signature (δ15N) of maize as well as soil parameters (pH, phosphatase activity, nitrate) in the field experiment. We analyzed phosphatase activities and rhizosphere pH by soil zymography and pH imaging in the rhizobox experiment. Maize N and P contents were larger in intercropping than monocropping, especially with soy and lupin in the field, indicating intercropping advantages for maize N and P acquisition. Intercropping with legumes decreased maize δ15N in the field, suggesting that 11–20% of maize aboveground biomass N was transferred from legumes to maize. Soil zymography revealed high phosphatase activities in the rhizosphere of lupin and faba bean. pH imaging showed a rhizosphere alkalinization by mustard, and a rhizosphere acidification by faba bean. These changes in the companions’ rhizosphere likely mobilized P and were also beneficial for maize in intercropping. Taken together, our study provides evidence that the companions’ ability to mobilize N and P in the rhizosphere promotes increases in maize nutrient contents and causes maize overyielding in intercropping and thus can contribute to fertilizer savings.
We aimed to investigate phosphorus (P) mobilization by different plant species from organic and inorganic sources in relation to different P mobilization mechanisms. Knowledge about P mobilization is important for producing crops on P sources other than phosphate rock-derived fertilizers. We conducted a greenhouse experiment with four plant species (maize, soy, lupin, mustard) and three P sources (FePO4, phytate, struvite). We determined pH and phosphomonoesterase activity in the rhizosphere using pH imaging and soil zymography. At harvest, root exudates were analyzed for phosphomonoesterase activity, pH, organic acids, and dissolved organic carbon (DOC). Plants were analyzed for biomass, root length, and P content. Struvite was more plant-available than phytate and FePO4 as indicated by higher plant P contents. Soy had the highest biomass and P content, irrespective of P source. Soy exuded up to 12.5 times more organic acids and up to 4.2 times more DOC than the other plant species. Lupin had a 122.9 times higher phosphomonoesterase activity than the other plant species with phytate. The pH in the exudate solution of mustard was on average 0.8 pH units higher than of the other plant species. P uptake by mustard and soy seemed to have also benefited from large root lengths. Taken together, our study indicates that soy has a particularly high potential to mobilize P from struvite and phytate, while mustard has a high potential to mobilize P from FePO4. Therefore, soy and mustard seem to be good options for agricultural production that relies less on phosphate rock-derived fertilizers.
Purpose: There is a need to develop agricultural practices that mobilize sparingly soluble soil phosphorus (P) due to increasing scarcity of P fertilizer. Interactions of different plant species in the rhizosphere might increase P mobilization, but the underlying mechanisms are still not fully understood. Methods:We conducted a pilot study with four plant species (maize, soy, lupin, mustard) grown alone and in combination with maize (intercropping) to investigate how species interact to mobilize P from iron phosphate (FePO 4 ). Root exudates of individual plants were collected and analyzed for low molecular weight organic acid anions (LMWOA) and pH.Results: Maize increased its exudation of LMWOA and its biomass P concentration in intercropping, especially when grown together with lupin. This is the first study to show unequivocally that a high LMWOA concentration in the rhizosphere in intercropping is not only caused by high LMWOA release of the companion but also by an increased LMWOA exudation of the main crop. The high release of LMWOA was associated with a higher maize P concentration, indicating that enhanced LMWOA release in intercropping is beneficial for P acquisition of maize. Moreover, lupin and mustard mobilized more P from FePO 4 than maize and soy likely through high LMWOA exudation (lupin) and rhizosphere alkalinization (mustard). Conclusion:Taken together, we reveal that intercropping with lupin increases the release of LMWOA by maize and concurrently the maize P concentration, suggesting that intercropping is useful for the mobilization of P from FePO 4 because it affects the exudation of maize.
<p>Keywords: Assemblage, Interaction, nutrients</p> <p>Forest fires can cause a temporary nutrient deficiency or imbalance in the soil. Post fire forest restauration could be enhance by simulating process of vegetation succession taking advantage of beneficial interaction between species (e.g. facilitation and complementarity), which could help coping with nutrient imbalances. To determine the type of interactions and their effects on soil nutrients affected by fires and on the acquisition of nutrients by plants, a meso-cosmos experiment was established under controlled conditions, using surface soils affected by the Cayumanque megafire (Regi&#243;n del Biobio). Seven assemblages of three species with different nutrient acquisition strategies were established: Nothofagus obliqua (mycorrhizae), Lomatia dentata (proteiform roots) and Sophora cassioides (nodules). In a complete factorial design of two blocks (with and without complementary fertilization). The main interactions resulted in competition between N. obliqua from S. cassioides and L. dentata, while S. cassioides was not be significantly affected by the presence of L. dentate, suggesting complementarity. Fertilization did not interact with assemblages or reduce competition, but increased plant growth in all assemblages. Available soil nitrogen (NO<sub>3</sub><sup>-</sup>) increased significantly in the presence of S. cassioides (6.88&#177;3.10) and decreased in the presence of L. dentata (2.67&#177;0.84). Finally, N. obliqua increased its nitrogen acquisition by 44% in the presence of L. dentata and decreased by 5% in the presence of S. cassioides. Although no significant differences were observed in P<sub>Olsen</sub>, the fraction of inorganic phosphorus was significantly lower in the presence of proteacea (122.24&#177;20.99). In addition, enzyme analysis showed no significant differences for microbial biomass and LAP activity. However, the combination of N.O. and L.D. showed significantly high phosphatase activity (16.36&#177;5.57).</p> <p>Finally, further isotopic and enzymes work is in process to study nutrient pools in plants and soil either of L. hirsuta and N. obliqua individuals growing alone or in combination. Because native Nothofagus spec. forests have been affected by forestry fires and replaced by plantations of exotic tree species throughout Chile, knowledge on interactions among native species affecting tree nutrition is lacking. Therefore, the results of our research support the use of plant assemblages as a potentially effective restoration strategy in post-fire soils with low nutrient content.</p> <p>Acknowledgement: Special thanks to National forestry institute, BayCEER and Yvonne Oelmann&#8217;s laboratory for contribute to this research and make it possible at an international scale. &#160;&#160;</p> <p>&#160;</p>
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