Effect of fertility levels and weed-management practices on yield potential, nutri- ent uptake and economics of spring-planted sugarcane (Saccharum officinarum)

A field experiment was carried out during the spring seasons of 200708 and 200809 at Muzaffarnagar, Uttar Pradesh to study the effect of NPK levels and weed-management practices on yield potential, nutrient uptake and economics of sugarcane ( Saccharum officinar um L.). The crop was fertilized with 75% recommended dose of fer- tilizer (RDF), 100% RDF (150:60:60 kg/ha of N: P O : K O) and 125% RDF in combination with 7 weed manage- 2 5 2 ment practices, viz. weedy check; weed free; three hoeing at 30, 60 and 90 days after planting; one hoeing at 30 days after planting followed by atrazine @ 2.0 kg a.i./ha; atrazine @ 2.0 kg a.i./ha as pre-emergence (PE) + 2,4-D @ 1.0 kg a.i./ha at 60 days after planting; glyphosate @ 1.0 kg a.i./ha at 25 days after planting + one hoeing at 60 days after planting and Sesbania sowing in inter-row space followed by 2,4-D @ 1.0 kg a.i./ha at 45 days after planting. The crop fertilized with 125% RDF being at par with RDF resulted in the highest cane yield and number of millable canes, being 15.5 and 22.3% higher respectively, than lower fertility level mainly because of remarkable improvement in individual cane weight, cane girth, cane length, tillering and lower mortality. The dose of 125% RDF was found economically more sound, as it generated the highest return of 86,740/ha with benefit: cost ratio of 2.35. The highest nutrient uptake by sugarcane and total nutrient removal by sugarcane + weeds was recorded with 125% RDF which was significantly higher over RDF. The total uptake of nutrients followed the trend similar to that of nutrient removal by sugarcane. Among the weed-management practices, 3 manual hoeings at 30, 60 and 90 days after planting being at par with the treatment post-emergence application of glyphosate @ 1.0 kg a.i. at 25 days after planting + one hoeing at 60 days after planting proved efficient in controlling the weed population and dry-matter production all the growth stages, as evident by the highest weed control efficiency. The cane yield, millable canes and nutrient removal were witnessed higher under glyphosate @ 1.0 kg a.i. at 25 days after plant- ing + one hoeing at 60 days after planting, followed by 3 manual hoeing at 30, 60 and 90 days after planting. Under weedy check plots, weeds removed the maximum nutrients, whereas lower uptake was observed under weed free conditions. Glyphosate @ 1.0 kg a.i./ha at 25 days after planting + 1 hoeing at 60 days after planting was the best weed-management practices for higher net return ( 91,067/ha) and benefit: cost ratio (3.60) when it was com- pared to other treatments.