No tillage affects the phosphorus status, isotopic composition and crop yield of Phaseolus vulgaris in a rain-fed farming system.
BACKGROUND
Conservation tillage promotes the accretion of soil organic matter and often leads to improved soil fertility and moisture availability. However, few studies have looked at the physiological response of crop plants to different tillage practices. It was therefore hypothesised that measuring the nutrient concentrations and stable isotope composition (δ(13)C, δ(18)O, δ(15)N) of shoots could help evaluate the physiological response of common bean (Phaseolus vulgaris L.) to different tillage treatments (no tillage (NT) and mouldboard ploughing (MP)) in a rain-fed farming system in northern Mexico.


RESULTS
NT significantly enhanced shoot phosphorus concentration in bean plants. Tillage exerted a negative effect on the extent of root colonisation (%) by arbuscular mycorrhizal fungi (AMF). Lower shoot δ(18)O but unchanged δ(13)C values in plants from the NT system suggest enhanced stomatal conductance but also enhanced photosynthetic rate, which overall resulted in unchanged water use efficiency. Bean plants in the NT system showed lower shoot δ(15)N values, which suggests that a larger proportion of total plant nitrogen was obtained through atmospheric nitrogen fixation in this treatment.


CONCLUSIONS
Greater diversity of AMF soil communities and heavier colonisation of roots by AMF in the NT compared with the MP system appeared to contribute to improved crop nutrition, water relations and yield in this rain-fed agroecosystem.
Alguacil
María Del Mar
Mdel M
CSIC, Centro de Edafología y Biología Aplicada del Segura, Department of Soil and Water Conservation, PO Box 164, Campus de Espinardo, E-30100 Murcia, Spain. mmalguacil@cebas.csic.es
Roldán
Antonio
A
Salinas-García
Jaime R
JR
Querejeta
José Ignacio
JI
D000383:Agriculture / Q000379:methods*; D018533:Biomass; D002244:Carbon / Q000378:metabolism; D003247:Conservation of Natural Resources; D018556:Crops, Agricultural / Q000382:microbiology / Q000502:physiology; D007554:Isotopes / Q000378:metabolism*; D008800:Mexico; D038821:Mycorrhizae; D009584:Nitrogen / Q000378:metabolism*; D009586:Nitrogen Fixation; D010100:Oxygen / Q000378:metabolism*; D027805:Phaseolus / Q000382:microbiology / Q000502:physiology*; D010758:Phosphorus / Q000378:metabolism*; D010788:Photosynthesis; D018514:Plant Structures / Q000378:metabolism / Q000382:microbiology; D011891:Rain; D012988:Soil Microbiology; D014867:Water / Q000502:physiology
D007554:Isotopes; D014867:Water; D010758:Phosphorus; D002244:Carbon; D009584:Nitrogen; D010100:Oxygen