Aims: To standardize crop spacing and irrigation requirements under different mulching situation for better yield and water productivity. Study Design: The experiment was designed in RBD with two replications. Place and Duration of Study: The experiment was conducted at Agronomic Research Station, Kerala Agriculture University (KAU), Chalakudy for three consecutive years from 2016 -17, 2017 – 18 and 2018 – 2019. Methodology: Study conducted with 18 treatments, includes three levels of irrigation, three types of mulching and with two different crop spacing. Observations on weed count and weed dry matter production were also taken to study the effect of different mulches on weed growth. Biometric observations of crop growth and yield were recorded. Results: Observations on biometric characters revealed that both the height and diameter of the crop canopy were significantly influenced by mulching and found to be highest in the plot where leaf was used as the mulching material and the yield of Amorphophallus during 2016 - 2017 showed that corm weight was greatly influenced by irrigation levels, mulching and spacing. Corm yield was lowest in the plot where irrigation frequency was once in three days (21.02 t/ha). Yield in leaf mulched plot was 38.11 t/ha while in plastic mulched and no mulched plots were 23.50 and 19.50 t/ha. Effect of treatments on water productivity and BC ratio showed that leaf mulching of the crop has significant effect. In leaf mulched plot, water productivity in 2016-17 was 2.03 while it was only 1.854 and 0.886 in 2017-18 and 2018-19. Similarly, BC ratio was highest for leaf mulched plot followed by no mulch and plastic mulch plot. Conclusion: The experimental results from 2016 -17, 2017 – 18 and 2018 – 2019, showed that Amorphophallus planted at a spacing of 90 cm x 90 cm, irrigated at a frequency of once in three days along with leaf mulching can increase the yield and water productivity along with effective control of weed population.

Rice Research Station, Vyttila, established 1958, was brought under the Kerala Agricultural University in 1974, with the mandates of crop improvement of saline-tolerant rice varieties and management of coastal saline rice tracts (Pokkali). Till date, 11 saline-tolerant varieties were released, which includes two pure line selection, three mutants, and one marker-assisted introgression.

Background: Pokkali is a versatile rice- fish system of cultivation, producing naturally organic rice along the waterlogged coastal regions of Kerala. The weed flora of Pokkali rice fields is different from other rice ecosystems. Diverse weed flora appears in low saline phase, when rice is cultivated, but they dry up and decompose in high saline phase. With time, significant deviations have been reported in various climatic parameters and as a result, the weed spectrum has also undergone changes. Methods: Two level stratified surveys and anotomical studies were conducted during Kharif 2017 and 2018 to study the weed flora in five major Pokkali growing blocks of Kerala. Two panchayaths (political village units) from each block and two padasekharams (group farming units) in each panchayath were selected for surveying. To understand the adaptive mechanism of weeds in saline soil condition, anatomical studies were performed on individual weed species. Result: Cyperaceae family dominated in the ecosystem with more number of species. Diplachne fusca and Eleocharis dulcis were the major weeds. Echinochloa crus-galli, a dominant weed reported in earlier weed survey was found confined to very few locations and the frequency got reduced from 80% to 12.5%. In addition, Sphenoclea zeylanica was observed as an emerging weed with notable morphological adaptations. Floating ferns like Najas graminea and Hydrilla verticillata caused problems to aeration in the water in fields.

VTL-3 is a tall high yielding saline tolerant rice variety developed by Rice Research Station, Vyttila in 1987, which is having a tendency to lodge at maturity. Researchers hence, developed semi-tall lines of VTL-3 using induced mutagenesis. The selected semi-tall mutants were screened with markers linked to Saltol QTL and it was found that this region was not affected in the mutant. A promising line selected after comparative yield trials was later released as VTL 10, Lavanya in the year 2018. In order to differentiate the variety Lavanya from its parent VTL 3, SSR marker analysis and DNA fingerprinting was carried out. These two varieties were screened with 48 SSR markers for DNA fingerprinting and eight markers were found to be polymorphic between VTL-10 andVTL-3. The polymorphic markers include RM600, RM3362,RM279, RM7, RM85, RM149, RM144 and RM1880. The number of alleles ranged from 1 to 3 and the size of PCR products ranged from 110 to 300bp with Polymorphic Information Content (PIC) from 0 to 0.38. From the present study, it was observed that these eight markers can be used to distinguish the mutant line VTL-10 from its original parent VTL-3.

A study was conducted at Rice Research Station, Vyttila to assess the effect of seed priming in improving the salinity tolerance of rice varieties. The study consisted of two parts. In the first part, screening of rice varieties for salinity tolerance was done and in the second experiment, the effect of priming on salinity tolerance was assessed. The first experiment was a laboratory study to screen three rice varieties, namely, Jyothi, Uma and Vyttila-10 at five salinity levels i.e., non-saline, 3 dS m-1, 6 dS m-1, 9 dS m-1 and 12 dS m-1. Results showed that Jyothi was susceptible to 6 dS m-1 salinity at 16 days after sowing (DAS). Uma was moderately tolerant and became susceptible to 6 dS m-1 at 21 DAS. Vyttila-10 was highly tolerant to 6 dS m-1 salinity but it was susceptible to the salinity level of 9 dS m-1 at 21 DAS. In the second experiment, seeds of these varieties were primed with three chemicals namely beta-amino butyric acid @ 1 mmol L-1, calcium chloride @ 2% and sodium nitroprusside @ 100 µM and with water as control. The seedlings of Jyothi and Uma were raised at salinity levels of 6 dS m-1 and 9 dS m-1, while seedlings of Vyttila-10 were raised at salinity levels of 9 dS m-1 and 12 dS m-1. The efficacy of each priming chemical was analyzed based on germination percentage, growth parameters and visual salt injury symptoms. Priming seeds with calcium chloride was found to improve the growth and salinity tolerance of rice seedlings and could be a reliable method to combat the salinity stress of rice in the initial stages of crop growth.

Pokkali system of cultivation, unique in the world, produces naturally organic rice in the coastal saline soils of Kerala. Rice-fish/prawn is the traditional system followed in this system. Over a decade, less attention is given to rice cultivation making the system less sustainable and leaving many fields barren. Ensuring more income per unit area from Pokkali fields is the only way to attract farmers back to Pokkali cultivation and to bring back the glory of the traditional farming system. To develop and demonstrate profitable new enterprises in the Pokkali ecosystem, a project was taken up including various integrating components. Different farming systems compared were rice alone (low saline phase), rice-fish rotational system and rice-fish + poultry system. A new model-floating duck cage (2 numbers) that can carry 50 ducks each was developed and installed over a field of one acre (0.4 ha), the average size holding of a marginal farmer. Duck droppings favoured the fish culture of Tilapia (Oreochromis niloticus) and the average size of fish increased by 476.5 g without any external feed. Production of eggs and meat by poultry increased farm income and contributed to the nutritional security of the neighbourhood. Duck released to paddy fields after harvest of rice reduced duck feed to a great extent (5 kg day−1 for 100 ducks). Increasing the income from rice fields by year-round utilization of the farm land by judiciously mixing fish + poultry with rice reduced the negative trend in the rice production front. The study proved that duck rearing is a viable component for integration in the rice-fish Pokkali ecosystem. Besides, rice-fish + duck farming system formed an important strategy for climate moderation by an additional transfer of C (average load of 3 kg organic matter per day by100 ducks) to the soil and enhancing other ecosystem services.

Pokkali is a unique rice farming system in coastal saline soils of Kerala. High Na content and the resultant wide ratio between Na and other cations, especially K, within the plant become detrimental for rice crop in these soils. An experiment was conducted at Rice Research Station, Vyttila during kharif 2018 to study the effect of liming and foliar application of K in reducing the Na/K ratio in Pokkali rice, adopting Randomised Block Design with 10 treatments replicated thrice and saline tolerant rice variety Vyttila 8. Treatments included two levels of lime (500 and 1000 kg ha-1) or dolomite (800 and 1600 kg ha-1) alone, and in combination, with foliar spray of sulphate of potash (SOP), 2% at 20 and 40 days after transplanting (DAT), foliar spray of SOP alone and control. The study indicated that application of lime at higher quantity, and foliar spray of SOP had significant influence on reducing the plant Na/K ratio. Number of tillers and panicles per m2, percentage of filled grain and grain yield were found to be higher on lime application @1000 kg ha-1 in combination with foliar spray of SOP, thereby enhancing the economic returns. Correlation analysis showed that grain yield and number of panicles had significant negative correlation with Na/K ratio at flowering. It was observed that flowering stage was the most critical one for maintaining a low Na/K ratio, which could influence the crop yield significantly.

A field study was undertaken at Agronomic Research Station, Chalakudy, Kerala for developing suitable water and weed management strategies for aerobic rice. The trial was laid out with three levels of irrigation in the main plot [irrigation at 10, 20 and 30 mm CPE (cumulative pan evaporation)] and five weed management treatments in the subplot (pre emergent herbicide oxadiargyl followed by hand weeding, 2,4- D sodium salt or bispyribac sodium at 20 days after sowing (DAS), hand weeding at 20 and 40 DAS and unweeded control). Irrigation at 10 mm CPE increased crop growth, but reduced weed growth. Less irrigation (30 mm CPE) favoured the growth and density of grasses and broad leaf weeds and produced the highest weed dry matter. Sedge population was more in frequently irrigated plot (10 mm CPE). Moisture stress in 30 mm CPE resulted in 44 per cent yield loss. Weed competition caused 64 per cent yield reduction. Both water and weeds together accounted for 85 per cent yield reduction. Irrigation at 10 mm CPE recorded the highest grain yield and weed control efficiency, but lowest water productivity. Among weed management practices, hand weeding at 20 and 40 DAS recorded the highest grain yield, weed control efficiency and water productivity. However, application of oxadiargyl followed by bispyribac sodium resulted in better water productivity and recorded highest B:C ratio.