S. Mani

Nutrients status in the surface and subsurface soils of dryland Agricultural Research Station at Chettinad in Sivaganga district of Tamil Nadu

A study on assessing the nutrient status of soils of Dryland Agricultural Research Station at Chettinad in Sivaganga District of Tamil Nadu was carried out to understand the relationship with various physico-chemical properties in surface and sub surface soil samples. Soil samples were collected at a depth of 0-15cm and 15-30cm and analyzed for available nitrogen, phosphorus, potassium, sulphur, DTPA extractable iron, copper, zinc, manganese and hot water soluble boron. The available N, P, K, S, DTPA extractable Zn, Cu, Mn and Fe ranged from 123.0-209, 14.0-28.0, 126.0-319.0 kg ha-1, 9.13-18.85, 0.10-3.52, 0.85-3.63, 24.02-49.21 and 8.9-22.38 mg kg-1 in surface soils, respectively. Generally the soils were low in N, low to medium in available P and medium to high in available K and S in the surface soils. The surface soils were deficient in DTPA extractable Zn and hot water soluble boron, and adequate in available Cu, Fe, Mn. Hot water soluble (HWS) boron status ranged from 0.36-0.44mg kg-1 in surface soils. The subsurface soils (15-30 cm) are low in available N, low in available P, low to medium in available K and S. The pH had significant positive correlation with EC, organic carbon and sulphur (r = 0.239*, 0.293* and 0.241*, respectively) and negatively correlated with CaCO3 (r =- 0.302**). Though the pH had positive correlation with CEC, available P, Zn and Mn but not significant and showed negative correlation with available N, K, Fe and B. Other physiochemical properties of soil showed either negative or positive non-significant correlation with available nutrient status.

Genesis, characterization and classification of some soils of semi arid tropical region of Tamil Nadu

The study was carried out in the three new research stations of TNAU with varied soil types with an objective to characterize and classify the some red, red laterite and black soils in semi arid tropical region of Tamil Nadu in relation to pedogenesis. The red soils were developed on weathered granite-gneiss parent material at gently sloping lands. The red laterite soils were developed on weathered granite-gneiss over laterite parent material at gently sloping lands to moderately steep sloping lands whereas the black soils were formed at nearly level or plain topography on granitic gneiss parent material mixed with calcareous murram. The red soils and red laterite soils are relatively more weathered than black soils. The red and red laterite soil colour varying from dark red to light reddish brown and dark reddish brown to light reddish brown, the black soils colour varying from very dark gray to dark grayish brown under dry and moist conditions, respectively. The soils are shallow (27 cm) to very deep (>170 cm). The surface horizons exhibited mostly medium fine granular to weak sub angular blocky structures whereas in subsurface horizons shown medium fine granular to medium strong sub angular blocky structures in red and red laterite soil pedons. The black soil pedons had coarse strong angular blocky structure. The textural class of fine earth fraction was clayey (52.9 to 64.3%) in black soils, whereas in red and red laterite soil pedons it was coarse textured gravelly sandy loam and sandy clay loam in the surface horizons and sandy loam, sandy clay loam and sandy clay in sub-surface horizons (54.5 to 73.7% sand and 16.5 to 40.9% clay). The silt content in most of the pedons showed an irregular trend with soil depth. Bulk density increased with increasing depth. The moisture retention at field capacity (33 kpa), permanent wilting point (1500 kpa) and available water capacity were high in black soils. Based on the morphology, physical, physico-chemical and chemical properties, the soils were classified as per USDA soil taxonomy into four orders viz., vertisols, alfisols, entisols and inceptisols.

Clay mineralogy and geochemistry of some black, red and red laterite soils in semi arid tropical region of Tamil Nadu

The X-ray diffraction pattern of soil clay fraction of one red soil pedon from Maize Research Station, Vagarai of Dindigul district, one black soil pedon from Cotton Research Station, Veppanthatai (Perambalur district) and one red laterite soil from Dryland Agricultural Research Station, Chettinad of Sivaganga district of Tamil Nadu was carried out to distinguish the distribution of clay minerals by using X-ray diffraction method and the mineral composition was assessed semiquantitatively. The black soil pedon revealed the dominance of smectite in association with small quantities of illite and kaolinite. The red soil pedon clay faction was “mixed” with smectite, illite and kaolinite type of clay minerals. The dominant clay mineral was kaolinite with small quantities of illite in red laterite soils pedon. The chemical composition of soils exhibited the siliceous nature with broad and large silica/sesquioxides and silica/ alumina ratios. The wider ratios of SiO 2 /R 2 O 3 and SiO 2 /Al 2 O 3 (4.64 to 5.61 and 5.75 to 6.94) were found in the black soils pedon followed by red soils pedon (4.55 to 5.01 and 7.78 to 9.64), respectively where smectite and illite were the dominant clay minerals. The narrow silica/ sesquioxides and silica/alumina ratios (2.23 to 2.56 and 4.13 to 5.37) were found in red laterite soils where Kaolinite was dominant clay mineral in semi arid tropical region of Tamil Nadu.

Application of fertility capability classification system in some black soils, red and red laterite soils of Tamil Nadu

Summary The study was carried out in the three new research stations of Tamil Nadu Agricultural University with varied soil types viz., Maize Research Station, Vagarai of Dindigul district, Cotton Research Station, Veppanthatai of Perambalur district and Dryland Agricultural Research Station, Chettinad of Sivagangai district of Tamil Nadu were selected for developing the strong soil resource database for proper appraisal of their productivity potential and their rational use. This study was an embodiment with an objective of application of fertility capability classification system in some black soils, red and red laterite soils of Tamil Nadu. Four fertility capability units were identified in the study area. The conditions modifiers identified in the study area were ‘d’ dryness, ‘v’ high clay content, ‘b’ basic reaction, ‘e’ low CEC and ‘i’ P fixation. The condition modifier ‘d’ were dominated in its occurrence followed by the condition modifier ‘e’, ‘b’ and ‘i’.

Effect of seaweed saps concentrates on nutrient content in cane, leaves and nutrient uptake of sugarcane.

A field experiment on sugarcane was conducted in 2012-13 to study the effect of seaweed saps of Kappaphycus alverizii and Gracilaria spp. were tested at different concentrations (2.5%, 5.0%, 6.25%, 7.5% and 10%) on nutrient content in cane, nutrient content in leaves and nutrient uptake by sugarcane. Significant improvement were observed in increasing nutrient content in cane, nutrient content in leaves and uptake by sugarcane at 10 per cent concentration of seaweed saps with recommended dose of fertilizer. Hence, the present study found that 10 per cent seaweed saps with recommended dose showed higher nutrient content in leaves, nutrient content in cane and nutrient uptake compared to other concentration.