Soil-inorganic nitrogen changes in rice fields under selected crop management interventions and hydrological conditions in Kilombero Floodplain, Tanzania
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Date
2017
Authors
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Journal ISSN
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Publisher
Sokoine University of Agriculture
Abstract
A study was conducted at Ifakara Morogoro Region with a purpose of investigating the
effect of selected crop management interventions and hydrological conditions on soil
NH4+ and NO3- content. Study sites were located at Valley Middle and Fringe sites as
distinct hydrological zones. An experiment, in a complete Randomized block design, with
six treatments: Semi-natural vegetation (TR1), Farmers practice (TR2), bunding alone
(TR3), bunding + 60 kgN/ha (TR4), bunding + 120 kgN/ha (TR5) and bunding+Lablab
green manure (TR6) was laid down in three replicates. SARO 5 rice variety was used as a
test-crop. The trials were set during the 2014/15 pre-season and 2015/16 main season.
Data was collected from 0-10cm soil depth. A Two-way ANOVA and post hoc – Tukey
HD test statistical analyses were performed using GenStat Programme. Pre-season NH4+
showed 3 patterns: initial increase to peak values within 3 and 6 weeks for the Fringe and
Middle sites, a period of decline (7th to 9th week, Middle, and 4th to 6th Fringe) and a
period of increase (from 7th, Fringe and 10th week, Middle). Highest peak NH4+ values
were at the Middle site (TR6 - 0.007401, TR5 - 0.004776, and TR4 - 0.04525, g/kg soil
and TR4 - 0.004524, TR5 - 0.004595 g/kg soil). Peak NH4+ values differed significantly
among treatments, following the trend: TR6>TR5>TR3>TR4>TR1>TR2 and
TR4>R6=TR5=TR3+TR2>TR1 at the Middle and Fringe sites, respectively. Nitrate
content decreased within 1-2 weeks both sites to attain the least values between 4 and 7
weeks and rose steadily to 10. Rice cropping season NH4+ and NO3- variation showed a
similar trend for both sites, apart for a sudden increase in the treatments with N input at
week 8 and 10. Hydrological conditions did not significantly influence the NH4+ and NO3-
(P = 0.05) content. The study recommends repeating the work under controlled conditions.
Description
A DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE
REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN
MANAGEMENT OF NATURAL RESOURCES FOR SUSTAINABLE
AGRICULTURE OF SOKOINE UNIVERSITY OF AGRICULTURE.
MOROGORO, TANZANIA.
Keywords
Soil-inorganic nitrogen, Rice fields, Crop management interventions, Hydrological conditions, Kilombero Floodplain, Tanzania