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Influence of Potassium‐Fertilization Rate and Form on Photosynthesis and N 2 Fixation of Alfalfa 1
Author(s) -
Collins Michael,
Duke Stanley H.
Publication year - 1981
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1981.0011183x002100040001x
Subject(s) - photosynthesis , human fertilization , biology , shoot , potassium , nitrogen , chlorophyll , agronomy , botany , horticulture , zoology , chemistry , organic chemistry
This study reports a growth chamber experiment conducted to investigate the influence of potassium (K) fertilization level (control, medium, high K) and form (KCI and K 2 SO 4 ) on photosynthesis, carbohydrate concentration, and N 2 fixation of alfalfa ( Medicago sativa L.). Fertilization with high levels of K as K 2 SO 4 increased shoot number per plant by 51% and increased shoot dry weight by 20% over the unfertilized control. Control plant herbage contained 1.28% reducing sugars (RS) compared with 0.78% RS in herbage of the high K‐high S treatment, indicating that K deficient plants accumulated these compounds in photosynthetic tissues. Chlorophyll concentration increased linearly in response to K application and net carbon exchange rate (CER) on a per plant basis was increased by average of 28% over the control. Nodule numbers per plant ranged from 28 for the control to 90 for the medium K‐high S treatment. Nitrogen‐fixation rate was enhanced by K fertilization and ranged from 12.3 nmoles ethylene/plant/minute for the control to 56.8 for the medium K‐medium S treatment. These results suggest that the increases in N 2 fixation of alfalfa in response to K and S fertilization are a result of a number of factors including increased CER, increased nodule numbers, and enhanced carbohydrate movement from the shoot.