Modelling the Effect and Variability of Integrated Weed Management of Phalaris minor in Rice-Wheat Cropping Systems in Northern India

Chun Liu,Makhan Singh Bhullar,Manpreet Singh,Shiv Shankhar Kaundun,Sriyapu Reddy Sreekanth Reddy,Tarundeep Kaur,Jitendra Kumar

doi:10.3390/agronomy11112331

Abstract

Phalaris minor Retz. (littleseed canarygrass) is the most problematic and herbicide-resistant weed in the rice-wheat cropping system in India. As such, it poses a severe threat to wheat yield and food security. A number of herbicidal and agronomic practices have been identified for the effective control of P. minor. These include crop rotation, crop establishment methods, herbicide spray technology, sowing time, weed seed harvest and effective herbicide mixtures. A population model of P. minor was built based on the life cycle of the species, herbicide resistance mechanisms and the effects of weed control practices. The model simulated the interactions of these factors and provided the best management recommendations for sustainably controlling this noxious weed species. Model results indicate that integration of chemical and non-chemical control methods was the most effective and sustainable strategy. For example, the integration of a happy seeder (a tractor-mounted mulching and sowing machine) with an effective post-emergence herbicide reduced the probability of weed control failure by 32% compared to the scenario with a rotavator and the same herbicide. Similarly, more conventional crop establishment methods such as a rotavator and conventional tillage could be accompanied by pre- or post-emergence applications of herbicide mixtures. Adoption of good herbicide spray technology and weed seed harvest delayed the onset of resistance evolution by up to four years. Furthermore, effective crop rotation such as the inclusion of sugarcane in place of rice in the summer season reduced the risk of resistance evolution by 31% within the 10 year simulation period. In addition to the scenarios using representative parameter values, the variability of model predictions was investigated based on some field experiments. The model provided a powerful tool for promoting Integrated Weed Management and the sustainable use of herbicides. Pragmatic ways of dealing with uncertainty in model prediction are discussed.

Highlights

Phalaris minor Retz. is the most common grass weed in wheat agro-ecosystems in India and was effectively managed by tillage, manual weeding and diversified crop rotations in the past
The probability of evolved resistance did not reduce within the 10 year time scale, the onset of resistance was effectively delayed by weed seed harvest (WSH)
We used a population model of P. minor to quantify the interactions of different chemical and agronomic weed control practices in an Integrated Weed Management (IWM) programme

Summary

Introduction

Phalaris minor Retz. is the most common grass weed in wheat agro-ecosystems in India and was effectively managed by tillage, manual weeding and diversified crop rotations in the past. Rice cultivation favours the persistence of P. minor [1], and growers have relied heavily on herbicides for the control of this weed. In 2017–2018, many growers in the rice-wheat belt sprayed the herbicides two to three times but still failed to control the weed. In some fields with high resistance levels, where herbicides have failed to control P. minor, the crops have sometimes been cut for fodder, resulting in huge financial loss to the growers. The increasing occurrence of multiple herbicide resistance indicates that relying on a single herbicide for long-term control of P. minor populations is unrealistic, and so Integrated Weed Management (IWM) strategies are recommended [11,12]. As “no two problems are the same—even in adjacent fields” [18], predictive models can help growers plan for appropriate responses while recognising the field-specific aspects of the weed control problem

Methods

Results

Conclusion