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Der Einfluß von Bewässerung und Fruchtfolge auf den Humus‐ und Stickstoffhaushalt sowie die Bodenproduktivität in der Gezira (Sudan)
Author(s) -
Jagnow G.
Publication year - 1973
Publication title -
zeitschrift für pflanzenernährung und bodenkunde
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 0044-3263
DOI - 10.1002/jpln.19731340104
Subject(s) - humus , vertisol , agronomy , nitrogen fixation , sorghum , chemistry , nitrogen , horticulture , biology , environmental science , soil water , soil science , organic chemistry
The influence of irrigation and crop rotation on the humus and nitrogen balance and soil productivity in the Sudan Gezira . Yields of Sorghum and Cotton, but not of Dolichos increased up to 3 times from the 10th to the 30th year in an unfertilized, irrigated field experiment on a vertisol with crop rotations of Cotton, Sorghum and Dolichos, esspecially after preceding years of bare fallow. Nitrogen fixation by root nodules and asymbiotic fixation by Azotobacter and blue green algae are discussed as a cause of the increased soil productivity. In a field pot trial with 2.5 cm layers of flooded soil 75 ppm of nitrogen were fixed in 12 weeks by blue green algae. On fertilization with 0.1% K 2 HPO 4 and 0.1% K 2 HPO 4 + 50 ppm Na 2 MoO 4 they fixed 244 and 290 ppm N respectively. Drying and reflooding the soil once to several times caused the N‐fixation to decrease steadily until it stopped with weekly dryings. Strong increases and decreases of organic C and N were observed in moist and also in dry field soil in different seasons as well as short term fluctuations of organic N in dry field soil.