Abstract
The use of carbonized rice husk biochar improves the fertility and productivity of poor soils in rice-based cropping systems. However, biochar may also influence weed seedling emergence and the efficacy of soil-applied herbicides. Experiments were conducted in a screenhouse to evaluate the effect of biochar rates (0, 20, 40, and 80 t·ha?1) and seed burial depth (0, 1, and 2 cm) on seedling emergence of junglerice (Echinochloa colona) and the effect of biochar rates and pendimethalin (0, 500, 1000, and 1500 g·a.i.·ha?1) and pretilachlor doses (0, 300, 600, and 900 g·a.i.·ha?1) on seedling emergence and seedling biomass of junglerice. Data were analyzed using nonlinear regression. The burial depth to inhibit 50% of maximum seedling emergence was 0.76 cm when biochar was not added to soil and the depth increased with an increase in biochar rates for soil. Similarly, compared with the soil with no biochar, the use of bichoar increased the pretilachlor dose to inhibit 50% of maximum emergence or biomass. The pretilachlor dose to inhibit 50% of maximum biomass of junglerice was 100, 130, 240, and 240 g·ha?1 when biochar was added at 0, 20, 40, and 80 t·ha?1. However, the efficacy of pendimethalin was not influenced by biochar rate. The results of this study suggest that rice husk biochar may increase weed seedling emergence from deeper burial depths and may decrease the efficacy of some soil-applied herbicides.
Highlights
Rice (Oryza sativa L.) is the most important crop in Asia and more than 90% of this crop is grown and consumed in Asia
The results of this study suggest that rice husk biochar may increase weed seedling emergence from deeper burial depths and may decrease the efficacy of some soil-applied herbicides
At 7 d after sowing (DAS), the greatest seedling emergence (a) from the soil surface was observed when biochar was added to soil at 80 t·ha−1 (70% emergence), whereas seedling emergence from the soil surface was 58% when biochar was not added to the soil (Figure 1 and Table 1)
Summary
Rice (Oryza sativa L.) is the most important crop in Asia and more than 90% of this crop is grown and consumed in Asia. Biochar can increase soil fertility, it may influence weed seedling emergence and the efficacy of soil-applied herbicides as the application of biochar decreases soil bulk density and increases organic matter [2, 4,5]. The use of biochar in such systems may inhibit or stimulate weed seedling emergence. Such information, is not available on rice weeds. Weed seedling emergence and herbicide efficacy may be influenced by the rates of biochar. Such information is not available in Asia on rice weeds. Of junglerice [Echinochloa colona (L.) Link], a common rice weed, from different seeding depths and the efficacy of two PRE herbicides on the weed
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