A century of weed change in New Zealand’s forage seed multiplication industry

Abstract

International seed trading provides a significant introductory pathway for weed seeds, and many globally established weeds originated as contaminants in agricultural seed lots. Management of these trade systems helps minimize agricultural losses and is an important means of preventing future biological incursions. Forage crop seed lots could be considered higher risk than seed lots of arable and vegetable crops, as they have been found to have a higher percentage of contaminated seed lots. Two of the most commonly used temperate forage crops worldwide are perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). New Zealand is one of the top producers of these crop seeds globally, and both species are commonly used in New Zealand pastures. Using historical and current seed lot analytical purity test results, we examined the frequency, identity and temporal changes of weed seeds found within agricultural seed lots of perennial ryegrass and white clover grown in New Zealand from 1912 to 2019. Overall, the percentage of contaminated forage seed lots decreased between approximately three to sixfold over the study period, indicating that herbicide availability, seed certification and improved crop management have been effective for weed control. However, we identified a handful of annual weed species that could become more problematic in the future, either because they showed an increasing presence trend in seed lots or were identified as the most common contaminants. In 2019, Vulpia bromoides was the most common contaminant in perennial ryegrass seed lots, and Chenopodium album was the most common in white clover seed lots. Sherardia arvensis and Poa annua, both significant species with an increasing presence trend, had the largest increases in perennial ryegrass seed lots over the study period. Conversely, Rumex acetosella had the largest presence decline for both crop species. There was a significant difference between the percentage of contaminant species that were grass weeds between study crops, where perennial ryegrass seed lots had approximately four times more grass species than white clover. Considering New Zealand trades crop seed with approximately half of the world’s countries and contributes substantially to the global supply of forage seed, our study provides a unique insight into changes of the weed spectrum throughout the seed for sowing system over the last century.

Evaluation and Selection of Bromegrass Genotypes under Phosphorus and Water Scarcity towards the Development of Resilient Agriculture Focusing on Efficient Resource Use

“…Identifying grasses exhibiting drought and nutrient scarcity tolerance will aid in the production of breed forage varieties which are better adapted to climate change [49,50]. In this regard, despite the high potential of bromegrass for producing high-quality forage in temperate regions, little attention has been paid to selecting more efficient genotypes in regards to water and nutrient use [51].…”

“…From cut number 4 onwards, there was a drop in dry matter production and, therefore, in P uptake as well, which affected both PUE and WUE (Figure S1). The superiority of L perenne could be related to the high domestication of this species, which began in the 17th century [50]. Some works have proposed that the domestication of species like wheat and corn has affected traits such as root architecture, improving their efficiency in both the uptake and use of phosphorus and water from the soil [71,72].…”