Thomas Biju Mathew

Comparative performance of four multi-purpose trees associated with four grass species in the humid regions of Southern India

The results of a field trial conducted at the Livestock Research Station, Thiruvazhamkunnu, Kerala to study the compatibility of different components in a silvo-pastoral system revealed that growth and yield of fodder species were significantly influenced by the tree components only after tree canopy formation. The fodder species such as Pennisetum purpureum Schum., Panicum maximum Jacq., Brachiaria ruziziensis Griseb. and Euchlaena mexicana Schrad. grown in association with Casuarina equisetifolia J. R. & G. Forst. and Ailanthus malabarica DC recorded comparatively higher forage yield even after canopy formation. However, forage crops grown in combination with Acacia auriculiformis A. Cunn. ex Benth. and Leucaena leucocephala (Lam.) de Wit. registered relatively lower values for growth and yield. Increased light infiltration into the understorey due to the cladophyllous canopy can be attributed as reason for the higher fodder productivity under Casuarina. Due to the combination of crown size and shape, tree height and spacing the amount of light intercepted by Ailanthus also was very low. Among the four multi-purpose trees used, Acacia recorded the maximum growth rate followed by Casuarina, Ailanthus and Leucaena. Forage productivity of the four species was in the order: Pennisetum purpureum > Panicum maximum > Brachiaria ruziziensis > Euchlaena mexicana. Casuarina with Pennisetum/ Panicm were found to be optimal tree — forage combinations for silvo-pastoral systems.

Effect of methods of irrigation and trash mulching on biophysico-chemical environs of soils in sugarcane agroecosystem

Results of the experiment conducted at Sugarcane Research Station, Thiruvalla revealed that all furrow irrigation had perceptibly increased the availability of soil moisture, reduced the soil temperature and improved the physical properties of soil. The availability of soil nutrients after the experiment increased appreciably with irrigation through all furrow method resulting in the enhancement of soil fertility. Alternate furrow irrigation had also recorded comparable values for above parameters. The treatments consisting of trash mulching either with all or alternate furrow irrigation had recorded higher values for the activity of soil enzymes like acid phosphatase, urease and cellulase and increased the microbial population of fungi, bacteria and actinomycetes. Trash mulching at 5 t ha−1 had also shown similar trends than unmulched plots. The skip furrow method of irrigation and Farmer’s practice of irrigating the crop once in a month without trash application had shown comparatively lower values for all the above parameters. It was observed that alternate furrow irrigation with trash mulching could economise the usage of water to the tune of 50 per cent during the formative phase of spring planted sugarcane without any loss in cane yield.

Effect of Time and Mode of Application of Potassium on the Growth, Yield and Quality of Sugarcane Ratoon

Studies were undertaken at Sugarcane Research Station, Thiruvalla during 1996–97, 1997–98 and 1998– 99 on ratoon crop of sugarcane to determine the effect of time and method of K application. The results revealed that soil application of K at 75 per cent of the recommended dose as basal along with 25 per cent of the recommended dose of K as foliar application at 90 DAP resulted in appreciable increase in millable cane count and cane yield. However, the juice quality remained unaffected with treatment effects. It was also observed that K application beyond 90 days after ratooning (DAR) either through soil or foliar application did not show any significant effects on cane yield and juice quality. Similarly 100 per cent K application as foliar spray could not enhance the cane yield and improve the juice quality.

Residual effects of sulphur nutrition on the ratoon crop of sugarcane

Residual effects of sulphur application on the ratoon crop of sugarcane were studied during 1998–1999 and 2000–2001. The application of sulphur at 60 kg ha-1 in the form of gypsum in the plant crop created residual effects on the growth and development of the ratoon crop and appreciably increased the cane and sugar yield. The cane yield increased to the tune of 8.47 and 10.37 per cent as compared to control. However, the residual effect of sulphur nutrition carried out to the plant crop was not reflected on the juice quality of ratoon crop.

Synergist induced susceptibility of tobacco caterpillar, Spodoptera litura (Fabricius) from Kerala, India exposed to conventional insecticides

The present study was undertaken to assess the insecticide resistance developed in various field collected population of S. litura and to induce susceptibility by using the synergists. Third-instar larvae collected from three different locations of Kerala viz., Thiruvananthapuram (TVM), Pathanamthitta (PTA) and Alappuzha (ALP) were exposed to conventional insecticides like chlorpyriphos, quinalphos, lambda-cyhalothrin and cypermethrin by leaf dip bioassay and resistance ratios were calculated by using the baseline data generated for respective insecticides using susceptible strain. Resistance ratios recorded were 1965, 840 and 320 against chlorpyriphos, 605, 255 and 59 against quinalphos, 926, 250 and 108 against lambda-cyahlothrin and 2566, 534 and 396 against cypermethrin respectively for TVM, PTA and ALP populations. The effect of selected synergists viz., piperonyl butoxide (PBO), diethyl maleate (DEM) and triphenyl phosphate (TPP) was studied in combination with respective test insecticides against the highly resistant population of S.litura collected from TVM of Kerala. The population was tested with insecticide in combination of the above synergists at different ratios. When PBO, TPP and DEM at ratio of 1:4 were used the synergistic ratio was 8.47, 7.26 and 3.98 for chlorpyriphos, 6.09, 5.26 and 3.05 for quinalphos, 13.37, 4.53 and 7.39 for lambda cyhalothrin and 4.77, 3.36 and 3.40 for cypermethrin respectively. PBO showed highest synergistic activity against both the organophosphates tested followed by DEM and TPP. Highest synergistic activity against synthetic pyrethroids also was shown by PBO, followed by TPP and DEM. The results obtained from the present study revealed that PBO at 1:4 ratio showed higher synergism with the test insecticides against the resistant populations of S.litura and proved to be an effective molecule alternate for breaking the resistance against conventional organophosphates and synthetic pyrethroids.

Effect of Methods of Irrigation and Mulching on the Quality and Productivity of Sugarcane

Results of the experiments conducted during 1998–1999 and 1999–2000 revealed that among the methods of irrigation, all furrow irrigation and alternate furrow irrigation had registered comparatively higher values for juice quality parameters like sucrose content, SMT Brix, CCS per cent and Purity coefficient with lesser content of reducing sugar, fibre content and titrable acidity. While with jaggery quality, the above methods of irrigation had shown numerically higher values for jaggery sucrose, jaggery Brix and jaggery purity. Mulching with trash at 2.5 t/ha had also improved juice and jaggery quality. Trash mulching with either all furrow or alternate furrow irrigation had appreciably increased sugar and jaggery production. The sugar and jaggery yield was drastically reduced in skip furrow irrigation and farmer’s practice without mulching.