ISSN:
1573-5036
Keywords:
humid tropics
;
N balance
;
N2 fixation
;
N fertilizer
;
nodulation
;
rice
;
rotation
;
soybean
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Abstract We report a study in northern Thailand to examine the effects of fertilizer N, applied both to paddy rice and to a subsequent soybean crop on symbiotic and yield characteristics of soybean and on the differences between inputs of fixed N2 and the removal of N as harvested product. Treatments were a factorial arrangement of 0, 100 and 300 kg N ha-1 applied to the rice (designated R0, R100 and R300, respectively), and 0,25 and 50 kg N ha-1, applied as ‘starter’ fertilizer to the soybean (S0, S25 and S50, respectively). Nitrogen applied to the rice increased rice yields by up to 74% but proportions recovered by the rice were low (45% [R100] and 14% [R300]). The rice N treatments had only marginal effects on soybean nodulation (up to 17% reduction in early growth) and above-ground dry matter (up to 9% increase). Effects on soybean seed yield and total N2 fixed were insignificant. Starter N, applied to the soybean at sowing, also marginally reduced nodulation and enhanced above-ground dry matter. Total N2 fixed was unaffected but seed yield was increased by up to 6%. For all treatments, total above-ground N ranged from 145 to 179 kg ha-1 with 72 to 85% (122 and 140 kg ha-1) derived from N2 fixation. When harvested product consisted of seed only, differences between inputs of fixed N2 and removals of seed N were close to zero (-10 to+9 kg N ha-1) with little effect of fertilizer N. The N balances were reduced by an average of 18 kg N ha-1 when straw was included as harvested product. We concluded that N applied to the rice and to the following soybean was inefficiently used by those crops and had only marginal effects of symbiotic activity of the soybean. Furthermore, the benefit of the N2 fixing soybean in this system was to slow the decline of, rather than enhance, the N fertility of the soil
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00029075
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