Field experiments were conducted with rice (ADT-39) during the wet Kharif season (July-October 2001) at two locations, the Tamil Nadu Rice Research Institute (TRRI) farm, Aduthurai (Vertisol) and the Agricultural Research Station (ARS) farm, Pattukkottai (Alfisol), representing the old and new delta areas of the Cauvery, respectively. The same set of treatments was followed in both soils. The treatments consisted of the recommended NPK fertilizer application at 75% and 100% alone, and 10 or 20 kg ha -1 humic acid (HA) in combination with NPK fertilizers as soil application, besides an integrated method involving soil application, root dipping and foliar spraying with humic acid and NPK fertilizers. Initial soil samples from the experimental fields were analysed for physical, physico-chemical and chemical properties. Surface soil samples were collected at critical growth stages and analysed for various available nutrients. The results of the field experiments revealed that the application of humic acid along with inorganic fertilizers led to higher soil nutrient availability at all the growth stages of rice. Similar results were obtained in both Vertisol and Alfisol. The present investigation concluded that the best treatment for soil nutrient availability was 10 kg ha -1 HA (soil application) + 0.1% HA foliar spray (twice) + 0.3% HA root dipping + 100% NPK, which was on par with the treatment involving 20 kg ha -1 HA (soil application) + 100% NPK compared to the other treatments.

The primary ecological effects of the eutrophication of upwelling in the nearshore waters are the triggering and sustenance of phytoplankton (diatom) blooms. Here, we present the changes in the morphological characteristics and body size of microautotrophs associated with the nutrient enrichment of coastal upwelling along the southwest coast of India. The FlowCAM data of microautotrophs representing two time series locations in the coastal environment along the southwest coast of India at 18 weekly/biweekly frequencies showed the following features. The most significant response of the microautotrophs to the eutrophication associated with coastal upwelling during the Southwest Monsoon (June-September) was an increase in their mean bio-volume, either by increasing the individual cell size or by forming large colonies. During the Southwest Monsoon, large colonies of Thalassiosira (~8 cells/colony), Thalassionema (> 16 cells/colony), and Asterionellopsis (> 8 cells/colony) become very abundant. Streptotheca formed large mat-like colonies (av. 192350 ± 348 μm 3 /individual), and Fragilariopsis grew as very long ribbons (av. 272997 ± 5071 μm 3 /individual). Large-sized Chaetoceros (av. 45715 ± 1273 μm 3 /individual) with longer setae were also plentiful during the Southwest Monsoon. All these changes in the morphology and life forms of microautotrophs would help them to rapidly assimilate nitrate under turbulent conditions during the Southwest Monsoon.

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Ferrogypsum is a waste from the effluent treatment plant of the titanium industry located in Tuticorin in south India. It contains gypsum (526.3 g/kg) and iron (102.4 g/kg as Fe2O3). It does not contain any heavy metal at a detectable level. To evaluate ferrogypsum as a soil amendment to alleviate sodicity, a field experiment was conducted on a sodic soil (fine mixed non-calcareous isohyperthermic very deep Vertic Ustropepts) with rice as the test crop. There were 7 treatments consisting of ferrogypsum as well as gypsum used either alone or in combination with farmyard manure or green manure, and a control. The grain and straw yields of rice were significantly increased over the control. Postharvest soil analysis revealed a significant reduction in pH (9.00 to 7.63) and ESP (37 to 14.9) due to soil reclamation with ferrogypsum or gypsum. Thus, ferrogypsum was as effective as gypsum in alleviating sodicity.