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Li L.,Key Laboratory of Plant and Soil Interactions | Li L.,China Agricultural University | Tilman D.,University of Minnesota | Lambers H.,University of Western Australia | And 2 more authors.
New Phytologist

Summary: Despite increasing evidence that plant diversity in experimental systems may enhance ecosystem productivity, the mechanisms causing this overyielding remain debated. Here, we review studies of overyielding observed in agricultural intercropping systems, and show that a potentially important mechanism underlying such facilitation is the ability of some crop species to chemically mobilize otherwise-unavailable forms of one or more limiting soil nutrients such as phosphorus (P) and micronutrients (iron (Fe), zinc (Zn) and manganese (Mn)). Phosphorus-mobilizing crop species improve P nutrition for themselves and neighboring non-P-mobilizing species by releasing acid phosphatases, protons and/or carboxylates into the rhizosphere which increases the concentration of soluble inorganic P in soil. Similarly, on calcareous soils with a very low availability of Fe and Zn, Fe- and Zn-mobilizing species, such as graminaceous monocotyledonous and cluster-rooted species, benefit themselves, and also reduce Fe or Zn deficiency in neighboring species, by releasing chelating substances. Based on this review, we hypothesize that mobilization-based facilitative interactions may be an unsuspected, but potentially important mechanism enhancing productivity in both natural ecosystems and biodiversity experiments. We discuss cases in which nutrient mobilization might be occurring in natural ecosystems, and suggest that the nutrient mobilization hypothesis merits formal testing in natural ecosystems. © 2014 New Phytologist Trust. Source

Zhao M.,Key Laboratory of Plant and Soil Interactions | Zhao M.,China Agricultural University | Tai H.,Key Laboratory of Plant and Soil Interactions | Sun S.,Key Laboratory of Plant and Soil Interactions | And 5 more authors.

Although recent studies indicated that miRNAs regulate plant adaptive responses to nutrient deprivation, the functional significance of miRNAs in adaptive responses to nitrogen (N) limitation remains to be explored. To elucidate the molecular biology underlying N sensing/signaling in maize, we constructed four small RNA libraries and one degradome from maize seedlings exposed to N deficiency. We discovered a total of 99 absolutely new loci belonging to 47 miRNA families by small RNA deep sequencing and degradome sequencing, as well as 9 new loci were the paralogs of previously reported miR169, miR171, and miR398, significantly expanding the reported 150 high confidence genes within 26 miRNA families in maize. Bioinformatic and subsequent small RNA northern blot analysis identified eight miRNA families (five conserved and three newly identified) differentially expressed under the N-deficient condition. Predicted and degradome-validated targets of the newly identified miRNAs suggest their involvement in a broad range of cellular responses and metabolic processes. Because maize is not only an important crop but is also a genetic model for basic biological research, our research contributes to the understanding of the regulatory roles of miRNAs in plant adaption to N-deficiency stress. © 2012 Zhao et al. Source

Wang Z.-G.,Key Laboratory of Plant and Soil Interactions | Bao X.-G.,Gansu Academy of Agricultural science | Li X.-F.,Key Laboratory of Plant and Soil Interactions | Jin X.,Key Laboratory of Plant and Soil Interactions | And 4 more authors.
Plant and Soil

Background: Overyielding (i.e., mixtures of crops yielding higher than expected when compared with monocultures) and increased nutrient acquisition have been found in many intercropping systems. However, there are very few published studies on long-term changes in soil chemical and biological properties in intercropping systems compared to sole cropping. Methods: A field experiment was established in 2003 in Gansu province, northwest China. The treatments comprised three intercropping systems (either continuous or rotational wheat/maize, wheat/faba bean, maize/faba bean intercropping), rotational cropping (wheat-maize, wheat-faba bean, faba bean-maize, and wheat-maize-faba bean rotations), and monocropping (sole wheat, faba bean and maize) systems. In 2011 (ninth year of the experiment) and 2012 (tenth year) the yields and some soil chemical and biological properties were examined after all crop species were harvested. Results: There was overyielding by 6.6 % and 32.4 % in wheat/maize intercropping in 2011 and 2012, respectively. Faba bean/maize intercropping was enhanced by 34.7 % and 28.6 %, respectively but not wheat/faba bean intercropping. Soil organic matter, total nitrogen, Olsen P, exchangeable K and cation exchange capacity in all intercropping systems did not differ from the monocultures except for soil pH in wheat/maize and faba bean/maize intercropping in 2011 and soil exchangeable K and cation exchange capacity (CEC) in 2012. Soil pH in wheat/maize and faba bean/maize intercropping was significantly reduced by 3.2 % and 1.9 %, respectively. Soil exchangeable K in wheat/maize, faba bean/maize and wheat/faba bean intercropping declined markedly by 15 %, 21.7 % and 12.1 %, respectively. Soil cation exchange capacity in wheat/maize, faba bean/maize and wheat/faba bean intercropping was notably lower than the corresponding monocultures by 17.5 %, 23.3 % and 18.3 %, respectively. Soil enzyme activities after 9 and 10 years of intercropping differed little from monocultures or rotations. Conclusions: The results indicate that intercropping overyielded compared with monocropping or rotational cropping and also maintained the stability of most of the soil chemical and enzyme activities relative to rotations and monocropping in the relatively fertile soil studied. © 2015, Springer International Publishing Switzerland. Source

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