TITLE:
Irrigation and Nitrogen Requirements of Wheat under Shallow Water Table Conditions of Asmara, Eritrea
AUTHORS:
Fekadu Tesfamichael, Ramesh Prasad Tripathi, Mehreteab Tesfai
KEYWORDS:
Evapotranspiration, Nitrogen, Supplementary Irrigation, Water Table Contribution, Water Table, Wheat
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.4 No.4,
April
26,
2016
ABSTRACT: Wheat (Triticum astivum L.) is traditionally
rainfed in Eritrea. Yields are low because of poor soil management and low
water and nutrient inputs. A field experiment was conducted in Akria farm,
located in the outskirts of Asmara. The
soil was clay loam associated
with non-saline shallow water tables fluctuating from 0.4 to 1.2 m depths
during the crop season. Wheat variety Wedel Nile was planted in split
plot design with four levels of supplementary irrigations (SI) viz. I1 (rainfed, 0 SI), I2 (1/3 of full SI), I3 (2/3 of full
SI), and I4 (full SI) in main plots and three levels of nitrogen
viz. N1 (18 kg N haǃ), N2 (50 kg N haǃ),
and N3 (100 kg N haǃ) as sub-plots in three
replications. Full SI refers to amount of water necessary to replenish soil
moisture deficit in the root zone from field capacity to 50% depletion of the
available soil moisture. Groundwater table was constant around 0.4 m depth for
32 days from planting and declined slowly thereafter. Wetness around 0.3 m
depth was thus near field capacity until second week of December and reduced
thereafter with declining water table. Average soil moisture depletion was 94
mm under rainfed and 64 mm under full irrigation. No symptoms of wilting were
observed in any of the treatments due to shallow water tables. Upward flux from
the water table was 4.6 mm·d-1 until 30 days from planting, which
declined to 0.2 mm·d-1 when the water table declined below 0.9 m
depth. Optimum yield of wheat (5603 kg·ha-1) was obtained by application
of 58 mm irrigation (I3) and 100 kg·ha-1 nitrogen
(N3). Total
water use for optimum yield of wheat was 382 mm and water use efficiency was 14.7 kg·ha-1·mm-1.
Contribution from water table to the evapotranspiration requirements of wheat
was highest (61%) under rainfed (I1) and lowest (52%) under full SI (I4).