15 



II. MICROBIOLOGY 



A. Nitrogen Fixation and Transformations 



Ala. Factors Affecting Microbiological Transformations of 

 Nitrogen as Related to Efficient Utilization of Legumes and 

 Fertilizer Nitrogen in Southern California. To learn (1) 

 factors influencing persistence of N fixing bacteria in soil 

 and establishment and maintenance of symbiotic relations 

 between orgaoiisms and roots of host legumes; and (2) influence 

 of soil and climatic factors on rate and magnitude of N 

 transformations, with reference to mineralization from 

 organic forms, nitrification, denitrif ication, leaching 

 losses, and non-symbiotic fixation. 

 Agron., Soils 574 (S-35) 



Ariz. Fixation of Nitrogen in Semi -Arid Soils, (l) Identify 

 soil algae responsible for N fixation in semi-arid soils; (2) 

 study habits of algae fixing N in pure culture & mixed culture- 

 as found under normal circumstances in rain-crust of soils; (3) 

 learn factors influencing the fixation of N in soils under lab. 

 & field conditions; (4) make microscopic examinations of surface 

 crust, involving identification & isolation of N fixing algae, 

 with main effort centered around soil algae; (5) make interrelation- 

 ship & associative studies between algae & soil fungi involved in 

 N cycle under controlled conditions in lab. where photosynthesis 

 is more favorable; and (6) conduct N balance studies on citrus 

 orchard soils to leam long-time build-up of N under different 

 cultural practices. 



Agr. Chem., Soils — (W-3I) 



Biological Decomposition of Nitrogen-Organic Matter Complexes 

 and Chemical Fixation of Amnonium Nitrogen by the Soil Organic 

 Fraction. To leam (l) relative availability of N fixed in com- 

 plexes resulting from chemical reaction between soil organic matter 

 & fertilizer N; and (2) reaction between inorganic N compounds & 

 soil organic matter involving fixation of N in an insoluble & 

 non -exchangeable form. 



Soils, Plant Nutr. 1723 (W-31) 



Factors Affecting the Establishment , . Activity and Persistence 

 of RhizobJQ in Soils. To study factors in introduction, effective- 

 ness and persistence of root nodule bacteria in soils with em- 

 phasis on the more important legume crops - 



Soils 702 Coop. USDA 



Effects of Low Temperatures on Nitrification of Ammonia in 

 Soils. Cl) Leam effects of temperature in range 30*^F. to 50°F. on 

 nitrification of NH3 in soils; (2) compare nitrification characteristics 

 of NH3 & certain amnoniacal salts at low temperature; (3) compare soil 

 pH changes resulting from nitrification of NH3 & certain anmoniacal 

 salts at low temperature; & (4) leam influence of soil type & related 

 characteristics on rate of nitrification of ammoniacal materials at 

 low temperature. 



Agron. 47 



