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Impact of Soil Amendments on Macronutrients (na, K, Ca, Mg, N and P) Contents of Rice Grain Under Subsurface Drainage in Salt Affected Soil

R Mandal
Department of Soil, Water and Environment, University of Dhaka, Dhaka-1000, Bangladesh

AC Aich
Benerpota Salinity Research Station, BWDB, Satkhira, Bangladesh

Abstract/ Executive Summary:

Impact of soil amendments and brackish water irrigation on grain of three cultivars of rice provided with subsurface drained and non-drained conditions in saline soil was investigated. Contents of Na, Mg, N and P of rice grain increased significantly with increasing brackishness of irrigation water (ECiw 0.7 to 5.0 dS/m) irrespective of drainage condition. The content of Na was found much lower in grain provided with subsurface drainage as compared with non drained ones irrespective of treatments and varieties. However, a reverse trend was observed in case of K. Addition of both lime and gypsum alone caused a decrease in Na and an insignificant increase in Ca concentration at all levels of brackish water irrigation. Effect of lime and gypsum in presence of organic matter did not influence very much in Na, Ca and Mg concentrations in all the cultivars. The contents of N and P increased with increasing levels of salinity might be due to stunted growth of plant caused by excessive Na. Lime and gypsum alone caused a decline in the P content whereas organic matter alone helped to increase the same in grain of rice. Application of lime and gypsum along with organic matter failed to respond in P content significantly in grain of rice in all grades of brackish water whether provided with subsurface drainage or not. In both the sets, cow-dung influenced better performance than straw in mineral nutrition of rice grain.

Keywords: Soil amendment, Rice grain, Macronutrients, Subsurface drainage, Salt affected soil

Location: Magura of Satkhira district.

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Soil salinity

Objectives:

To see whether the application of organic, inorganic and physical amendments could possibly suppress the uptake of Na and help to enhance the accumulation of other macronutrients of rice grain.

Methodology:

The land was divided into four blocks, two for non-drainage and the other two for subsurface drainage. Then each block was divided into three subblocks for irrigation with three grades of brackish water. Each irrigation subblock was further subdivided into three plots for two sources of organic matters and one for minus organic matter. Each plot was again divided into three split plots for gypsum, lime and without gypsum and lime. These split plots were further subdivided into three strips for three varieties of rice. The size of each strip plot was 4m² . The treatment combinations used were as follows. Brackish irrigation water (EC iw); Low (0.7 dS/m); medium (2.50 ds/m) and high (5.0 dS/m). Cow-dung (CD) and Straw (Str) : CD 0 Str 0 = Organic Matter (0 t/ha), CD = (10 t/ha) and Str = (10 t/ha). Gypsum (G) and lime (L): G 0 L 0 = (0 t/ha), G = ( 0.5 t/ha) and L = ( 0.5 t/ha) Rice cultivars: BR3, BR15 and Iratom 24. A total of 81 treatment combinations were arranged according to 3⁴ factorial split strip plot design with two replications . Each subblock was separated by 2 meter buffer zone and each plot was surrounded by a 1 m wide ridge. PK (80: 60 kg/ha) and one third of the N (90 kg/ha) was applied as basal dose and the rest two-third of N was top dressed in two equal splits one at 30 days after transplantation (DAT) and the rest at 60 DAT. The organic matters were added seven days prior to transplantation and kept at field moisture condition. Gypsum and lime were applied on the surface soil of the plots at the time of final land preparation. Thirty five days old healthy seedling were transplanted as three seedlings in each hill spaced at 20cm × 20cm. The experimental blocks were irrigated with water of EC 1.2 dS/m during land preparation and also a ten days more after transplantation (survival stage), following by submergence of 2-5 cm standing water with brackish irrigation water. Installation of subsurface drainage: For installation of subsurface drainage, trenches were made manually to a depth of 0.75m and with a spacing of 2m. Uniform bamboos were selected. The average internal diameter of the bamboo was 65 mm. The bamboos were splinted into two equal halves longitudinally. Internal nodes were carefully removed and half was bored (0.5 mm dia) at an interval of 15 cm in a single line and the halves put together again and tied by nylon rope. A nylon net was used to cover the bamboo logs for protection against entrance of foreign material into the log. Prepared bamboo logs were then placed on the ready trenches in such a way so that perforated halves remain on the top side with a slop of 0.1% and rice straw was spread around the logs. Cutout soils were replaced in the same order as was dugout. For consolidation of the fill soils surface irrigation was given manually with water of EC 1.2 dS/m. The drainage logs were connected to outlet placed at 1m depth from the surface. Analytical techniques: Grain sample of rice was digested by diacid mixture of HNO₃ and HCIO₄ in 5:2 ratio. For chemical analysis of Ca, Mg, Na, K and P. Determinations were made of Ca and Mg by Atomic Absorption Spectrophotometer (model Hitachi 170-10), Na and K by Flame Emmission Spectrophotometery using a Flame Photometer (model corning EEL) and P as vanadomolybdophosporic acid complex spectrophotometrically. N in a separate portion of grain sample, digested by H₂SO₄ and HCIO₄ mixture, was estimated colorimetrically by Auto Analyzer (Technic S.O. colorimeter).

Source of Information: DUJBS 2010; 19(1): 1-11

Article Link (Online Journal): DOI: http://dx.doi.org/10.3329/dujbs.v19i1.8938

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The content of N in grain increased significantly due to the application of gypsumnd lime in all grades of irrigation waters, though a few data were not significant. The increase of N and P content due to brackishness had happened haply due to the stunted growth of the plant caused by excessive Na and possibly the uptake of N and P remained the same but the growth was not so much as in low brackish water.

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