Authors:M. Jayakumar, S. Khrisnasamy and N. Thavaprakash
Field experiments were conducted at the Central Farm of the Agricultural College and Research Institute, Madurai, India during the rabi (October-January) seasons of 1999-2000 and 2000-2001 in a split plot design with three replications. The soil of the experiments was sandy clay loam with a neutral reaction. The main plot consisted of six irrigation schedules with mid-season drainage, while four N splits were taken as sub- plots. The experimental results revealed that irrigation to a depth of 5 cm one day after the disappearance of ponded water and mid-season drainage, along with N applied in four splits, with 16.7% at 10 days after transplanting, 33.3% at active tillering, 33.3% at panicle initiation and 16.7% at the heading stage, produced significantly higher growth, yield attributes, grain and straw yields in hybrid rice. A combination of the above treatments led to maximum grain yields of 7533 and 8078 kg ha-1 (45.53 and 45.86% in excess of the control) in 1999-2000 and 2000-2001, respectively.
Authors:M. Raju, B. J. Pandian, P. Thukkaiyannan and N. Thavaprakash
Field experiments were conducted at the Agricultural College and Research Institute, Tamil Nadu Agricultural University, Killikulam, India during the kharif (July to November) and summer (December to April) seasons of 1999 and 2000 in a randomized block design. The treatment consisted of three pre-emergence herbicides (pretilachlor + safener 0.3 kg ha-1 4 days after sowing [DAS], butachlor 1.0 kg ha-1 8 DAS and pendimethalin 1.0 kg ha-1 8 DAS) and one early post-emergence herbicide (butanil 3.0 ha-1 15 DAS), each in combination with mechanical or hand weeding 30 and 45 DAS. In addition, green manure (Daincha) intercropping and incorporation, mechanical and hand weeding twice alone (25 and 50 DAS) were compared with the unweeded check. The results revealed that the pre-emergence application of pretilachlor + safener 0.3 kg ha-1 + hand weeding twice (30 and 45 DAS) promoted higher yield attributes and maximum yield in wet-seeded rice.
Authors:N. Thavaprakash, G. Senthilkumar, S. D. Sivakumar and M. Raju
A field experiment was conducted at the Main Research Station, University of Agricultural Sciences, Dharwad, India, on medium black soils during the kharif (wet) season of 1999. The experiment was laid out in a randomized complete block design with varying N/P ratios (0.67 to 2.00) along with a control with a constant level of potassium (60 kg ha-1). The results revealed that the number of green leaves plant-1, the dry matter accumulation in the leaves, leaf area (dm2 plant-1) and leaf area index (LAI) increased up to the flowering stage (65 DAS) and thereafter declined. In the early stages (seedling and button stages) there was no significant variation with respect to the number of green leaves plant-1 among the treatments except in the control. Similarly, leaf area and LAI did not vary at the seedling stage. Treatments receiving N/P ratios of ?1.0 or 1.0 with higher doses of nitrogen (120 kg N ha-1) gave a significantly higher number of green leaves plant-1, leaf area and LAI as compared to N/P ratios of <1.0 and the control in later stages. The dry matter accumulation in the leaves (g plant-1) differed in all the stages, but higher values were recorded in these same treatments. Thus, due to the higher number of green leaves, higher LAI and greater dry matter accumulation in the leaves, the treatments with an N/P ratio of ?1.0 or 1.0 with 120 kg N ha-1 produced higher seed yields (3188 to 3554 kg ha-1) than other N/P ratios (2761 to 3009 kg ha-1). The highest yield (3554 kg ha-1) was recorded with an N/P ratio of 1.0 in the treatment receiving 120 kg N and 120 kg P2O5 ha-1. The correlation coefficients between these photosynthetic attributes and seed yield were also positive and significant.