Effect of Sources of Organic Manure and Levels of N and P on Weed Infestation and Dry Matter Production of Cassava in Lowlands

A study was undertaken at Integrated Farming System Research Station, Karamana, Thiruvananthapuram, Kerala during 2017–18 to study the effect of sources of organic manure including green manuring in situ and levels of N and P on weed infestation and dry matter production of cassava in lowlands. The practice of green manuring in situ with cowpea, raised along with cassava, reduced weed infestation in cassava and improved its growth and yield. Application of higher level of N (75 kg ha⁻¹) resulted in higher weed dry weight and density, but produced higher dry matter of cassava. There was no marked variation in weed infestation due to P levels. However, application of lower level of P (25 kg P₂O₅ ha⁻¹) resulted in higher dry matter production. Combined application of poultry manure @ 2.5 t ha⁻¹ + green manuring in situ (M3) + 75: 25: 100 kg NPK ha⁻¹ registered lower weed infestation and highest tuber yield and dry matter production of cassava in lowlands.