Soil water deficiency and biological Nitrogen fixation in common bean crop Phaseolus vulgaris L

Abstract

The identification of the stages of the cultivation of beans (Phaseolus vulgaris L.), in which water deficiency reduces the biological fixation of nitrogen BNF, took place in field trials in a soil Typic Haplustoll, loamy sand of La Tola Experimental Center, Pichincha, Ecuador. The average annual temperature in the location is 15 ºC with a relative humidity of 74%, at an altitude of 2465 meters above the sea level. 123 mm of rainfall were recorded during the period of the experiment (July at November 1995). The moisture regime treatments were as follows: S1 = normal irrigation throughout the cycle, S2 = deficit irrigation throughout the cycle, S3 = water stress during vegetative growth (20-50 days after planting dap), S4 = water stress during flowering (53-81 dap), S5 = water stress during pod filling (82-110 dds), and S6 = water Stress during ripening (111-130 dap). The soil moisture was measured with a neutron probe up to 0.40 m depth, 24 h before and after watering. The BNF was estimated with the methodology of N-15. The results indicate that the water stress during the entire cultivation (S2), during flowering (S4) and during the filling of pods (S5) significantly affected the biological nitrogen fixation in the cultivation of beans. The restriction of watering during the vegetative growth (S3) and the maturation of grain (S6) not significantly reduced biological nitrogen fixation, reaching values of 38%, statistically similar to the cultivation with a normal irrigation throughout the cycle (S1) regime.

Keywords

• irrigation
• water stress
• biological nitrogen fixation
• neutron probe
• common bean
• phaseolus vulgaris.