Plant population and weed control effects on bulb size distribution of onion (Allium cepa L.) under chicken weed (portulaca quadrifida L.) infested field

Abstract

Plant population and weed management are among major factors constraining onion production. Therefore, field trial was conducted in Birnin Kebbi, Nigeria during the 2017/2018 and 2018/2019 dry seasons to assess the bulb size distribution of onion under the influence of plant population and weed control practice. The treatments was made of three plant population (500,000, 333,333 and 250,000 plants/ha) and weed control methods (pendimethalin @ 1.0 kg a.i. ha-1 + 1 Hw: pendimethalin @ 1.5 kg a.i. ha-1: pendimethalin @ 2.0 kg a.i. ha-1: butachlor @ 2.0 kg a.i. ha-1 + 1 Hw: butachlor @ 2.8 kg a.i. ha-1: butachlor @ 3.6 kg a.i. ha-1: fluaxifop-P-butyl @ 2.0 kg a.i. ha-1: oxyfluorfen @ 1.0 kg a.i. ha-1 + 1 Hw: two weeding at 3 and 6 weeks after transplanting (WAT): three weeding at 3, 6 and 9 WAT: weed free and weedy check). The experiment was laid out in Randomized Complete Block Design and replicated three times. Results showed that onion bulb size distribution was not significantly affected with plant population treatments. The use of pendimethalin and butachlor at 1.0 and 2.0 kg a.i. ha-1 two days after transplanting followed by one hoe weeding respectively at 6 WAT recorded the highest bulb size distribution of onion. Weeding 3 times was second best and it can serve as an alternative to the aforementioned practice. It can be concluded that the integration of two methods such as pendimethalin at 1.0 kg a.i ha-1 or butachlor at 2.0 kg a.i ha-1 followed by one hoe weeding at 6 WAT was significantly superior to other methods and therefore, recommended for onion farmers in the study area as best practice for weed control.