iHSD Mill Efficacy on the Seeds of Australian Cropping System Weeds

Abstract

In Australia, widespread evolution of multi-resistant weed populations has driven the development and adoption of harvest weed seed control (HWSC). However, due to incompatibility of commonly used HWSC systems with highly productive conservation cropping systems, better HWSC systems are in demand. This study aimed to evaluate the efficacy of the integrated Harrington Seed Destructor (iHSD) mill on the seeds of Australia’s major crop weeds during wheat chaff processing. Also examined were the impacts of chaff type and moisture content on weed seed destruction efficacy. Initially, the iHSD mill speed of 3,000 rpm was identified as the most effective at destroying rigid ryegrass seeds present in wheat chaff. Subsequent testing determined that the iHSD mill was highly effective (>95% seed kill) on all Australian crop weeds examined. Rigid ryegrass seed kill was found to be highest for lupin chaff and lowest in barley, with wheat and canola chaff intermediate. Similarly, wheat chaff moisture reduced rigid ryegrass seed kill when moisture level exceeded 12%. The broad potential of the iHSD mill was evident, in that the reductions in efficacy due to wide-ranging differences in chaff type and moisture content were relatively small (≤10%). The results from these studies confirm the high efficacy and widespread suitability of the iHSD for use in Australian crop production systems. Additionally, as this system allows the conservation of all harvest residues, it is the best HWSC technique for conservation cropping systems.

Opportunities and challenges for harvest weed seed control in global cropping systems

“…Therefore, more recent efficacy studies have focused on introducing known quantities of annual ryegrass seed, stained with food dye, directly into the chaff material prior to HWSC treatment. For example, stationary unit and commercial harvest testing of impact mills (iHSD and HSD), involved the introduction dyed weed seeds into the chaff stream as it entered the mill . Preliminary studies examining the efficacy of chaff tramlining and chaff lining have investigated the survival of weed seeds in mesh packets placed on the soil surface beneath chaff rows.…”

“…24 Testing of this system has confirmed similarly high weed seed destruction levels as the tow-behind HSD unit (Table 2). 25,26 wileyonlinelibrary.com/journal/ps…”

“…For example, stationary unit and commercial harvest testing of impact mills (iHSD and HSD), involved the introduction dyed weed seeds into the chaff stream as it entered the mill. 23,25,26 Preliminary studies examining the efficacy of chaff tramlining and chaff lining have investigated the survival of weed seeds in mesh packets placed on the soil surface beneath chaff rows. These packets are extracted periodically for seed viability assessment.…”

“…The iHSD mill is powered by the harvester and with an estimated power requirement of 54 kW, that currently restricts its current use to larger harvesters . Testing of this system has confirmed similarly high weed seed destruction levels as the tow‐behind HSD unit (Table ) …”

Seed retention of winter annual grass weeds at winter wheat harvest maturity shows potential for harvest weed seed control

“…To replicate harvester-produced material, the chaff was passed through a combine. Similar to Walsh et al (2018a), before processing with the iHSD mill, 1,000 seeds of a weed species were mixed with 2 kg of wheat chaff. A single seed lot for each species was used, obtained from collections at the Colorado State University Weed Research Laboratory made in 2015.…”