Production potential of pulses in summer rice fallows under conservation tillage

Abstract

An experiment entitled “Production potential of pulses in summer rice fallows under conservation tillage” was undertaken at the Department of Agronomy, College of Agriculture, Vellayani during 2023 – 25. The objective were to evaluate the production potential of pulses in summer rice fallows under conservation tillage, and to assess the weed dynamics. The field experiment was conducted at the Integrated Farming System Research Station, Karamana during February to May 2025. The experiment was laid out in Split Plot Design with three replication. The main plot treatments were five tillage methods (M) viz., M1- Minimum tillage (primary tillage only), M2- Zero tillage with surface seeding followed by bio-mulching using aquatic weeds (5 t ha-1 on fresh weight basis) at 15 DAS, M3- Minimum tillage + post-emergence herbicide (imazethapyr + imazamox @ 80 g ha-1 at 20 DAS), M4- Conventional tillage + two hand weedings at 15 and 30 DAS, and M5- Conventional tillage + imazethapyr + imazamox @ 80 g ha-1 at 20 DAS and the subplots were two pulse crop (C) viz., C1- Green gram (CO 8) and C2- Black gram (CO 6). The crops were raised as per the package of practices recommendations of Kerala Agricultural University (KAU, 2024). Bio-mulching was done using aquatic weeds comprising Limnocharis flava (60%), Pistia stratiotes (10%) and other weeds (30%). The predominant weed flora of the experimental field was broad-leaf weeds followed by grasses and sedges. The growth parameters such as plant height, number of branches, number of leaves and dry matter production were recorded at 30 DAS, flowering, and at harvest. The growth attributes of both crops were significantly influenced by tillage methods and their interactions. Among tillage methods, taller plants were observed in M1, M2 and M4 at 30 DAS. At flowering, M1 and M2 were on par while at harvest, all treatments were on par except M4. Between the pulse crops, taller plants were observed in green gram (C1) at flowering and at harvest. At harvest, the highest number of branches were recorded in m5c2. Among tillage methods, more number of leaves were observed in M3, M4 and M5 at flowering. Black gram recorded the highest number of leaves during all growth stages. At 30 DAS, dry matter production was higher in M2 and M1 while at flowering and at harvest, higher values were recorded in M5, M4 and M3. The highest

dry matter production per plant was recorded in black gram at flowering (10.31 ± 0.90 g) and at harvest (22.25 ± 2.95 g), respectively. The highest number of nodules (25.33 ± 2.52) at flowering was observed in black gram under conventional tillage (m4c2). The physiological parameters viz; crop growth rate (CGR), relative growth rate (RGR), and leaf area index (LAI) were significantly influenced by tillage method. Higher CGR at 15–30 DAS was recorded in M2, which was on par with M1, while M5 recorded higher CGR at 30-45 DAS and at 45-60 DAS which was on par with M3 and M4. Black gram recorded higher CGR at 45-60 DAS. The RGR was higher in M5 at 30- 45 DAS, which was on par with M3 and M4. At 30 DAS, M2 and M4 recorded higher LAI, while at 45 DAS higher LAI was observed in M4, M3 and M5, respectively. Black gram recorded the highest LAI at 30 DAS and at 45 DAS. Yield and yield attributes were significantly influenced by treatments. The mean number of days to 50 per cent flowering varied from 35 to 45. The treatment combination m1c2 and m2c2 took less number of days for flowering. Among tillage method M3, M4 and M5 recorded more number of pods per plant. Between the pulses, black gram recorded higher number of pods (35.11 ± 9.73) and 100 seed weight. Among tillage methods, M5 recorded higher seed yield (1007 ± 210.68 kg ha-1) which was on par with M3 and M4. The percentage increase in seed yield in M5, M4, M3 and M2 were 68 per cent, 61 per cent, 56 per cent and 7 per cent, respectively over minimum tillage (M1). Black gram recorded higher seed yield (968 ± 229 kg ha -1) which was 41 per cent more than green gram. Higher harvest index was observed in M3, M4 and M5. The weed density varied with tillage method and pulse crop. Lower weed density was observed in M4 which was on par with M3 and M5. The lowest weed dry weight was observed in M4 at 30 DAS and at 45 DAS. Weed density, weed dry weight and nutrient removal by weeds were lower in black gram during all growth stages. At 45 DAS, nutrient removal by weeds was lower in M4 which was on par with M3 and M5. The nutrient uptake and soil properties were significantly affected by the treatments. Higher N and K uptake was observed in M3, M4 and M5 while higher P uptake was observed in M3 and M5. Between the pulses, black gram exhibited higher

N, P and K uptake and soil dehydrogenase activity. The available N and organic carbon were higher in M2 which was on par with M1 and M3. The highest dehydrogenase activity was observed in zero tillage (M2). From the experiment, it was concluded that green gram grown in summer rice fallows performed superior under minimum tillage with post-emergence application of imazethapyr + imazamox at 80 g ha⁻¹ at 20 DAS, resulting in higher yield, profitability, and effective weed control under conservation tillage. In black gram, conventional tillage coupled with post-emergence application of imazethapyr + imazamox at 80 g ha⁻¹ at 20 DAS proved superior in terms of yield, economic returns, and weed suppression