In perennial ryegrass (Lolium perenne L), annual and seasonal dry matter yield (DMY) and nutritive quality of herbage are high-priority traits targeted for improvement through selective breeding. Genomic prediction (GP) has proven to be a valuable tool for improving complex traits and may be further enhanced through the use of multi-trait (MT) prediction models. In this study, we evaluated the relative performance of MT prediction models to improve predictive ability for DMY and key nutritive quality traits, using two different training populations (TP1, n = 463 and TP2, n = 517) phenotyped at multiple locations. MT models outperformed single-trait (ST) models by 24% to 59% for DMY and 67% to 105% for nutritive quality traits, such as low, high, and total WSC, when a correlated secondary trait was included in both the training and test set (MT-CV2) or in the test set alone (MT-CV3) (trait-assisted genomic selection). However, when a secondary trait was included in training set and not the test set (MT-CV1), the predictive ability was not statistically significant (p > 0.05) compared to the ST model. We evaluated the impact of training set size when using a MT-CV2 model. Using a highly correlated trait (r g = 0.88) as the secondary trait in the MT-CV2 model, there was no loss in predictive ability for DMY even when the training set was reduced to 50% of its original size. In contrast, using a weakly correlated secondary trait (r g = 0.56) in the MT-CV2 model, predictive ability began to decline when the training set size was reduced by only 11% from its original size. Using a ST model, genomic predictive ability in a population unrelated to the training set was poor (r p = −0.06). However, when using an MT-CV2 model, the predictive ability was positive and high (r p = 0.76) for the same population. Our results demonstrate the first assessment of MT models in forage species and illustrate the prospects of using MT genomic selection in forages, and other outcrossing plant species, to accelerate genetic gains for complex agronomical traits, such as DMY and nutritive quality characteristics.

Runoff potential of 5 herbicides (acetochlor, atrazine, hexazinone, pendimethalin, and terbuthylazine) was evaluated in a small-scale study under simulated rainfall on a cultivated Hamilton clay loam soil. At 24 h after herbicide application, rainfall events of different intensities were simulated to 0.5-m2 field plots with 20% (70, 88, and 111 mm/h) and 30% (60, 70, and 80 mm/h) slope, respectively. The objective of this study was to compare the behaviour of pesticides covering a range of properties under identical hydrodynamic conditions. Sediment amounts and herbicide concentrations were determined in the runoff samples. As the transported sediment amounts were not sufficient for chemical analyses, herbicide residues attached to sediment were estimated using Kd values determined locally for the soil. Whereas pendimethalin concentrations followed no noticeable pattern, the concentrations for the other herbicides were highest in the first runoff samples, and decreased exponentially with further rain. Results show that herbicides were primarily transported in their dissolved form with the exception of pendimethalin. Slope affected cumulative runoff, sediment, and herbicide losses significantly (P < 0.05). The impact of increased rainfall intensity on runoff initiation followed a similar trend, but herbicide losses from plots exposed to different intensities were not always significant. Losses dissolved in runoff from plots with 20% slope were ≤1% of the applied herbicide, whereas on plots with 30% slope the maximum recorded loss was 65%. Here, losses for all herbicides ranged between 1 and 7% at 60 mm/h and 8 and 65% at 80 mm/h. Exports of herbicides with moderate solubility were negatively correlated with their Kd values and their water solubility.

To quantify soil residual activity and plantback periods for two maize herbicides saflufenacil and topramezone different rates were applied to a cultivated soil and samples (05 cm) collected at regular intervals for glasshouse bioassays Phytotoxic residues of saflufenacil applied at 17 g ai/ha the rate used for conservation tillage and pasture renovation persisted in the soil for lt; 2 weeks for the susceptible species viz white clover onion carrot and radish Residual activity from 102 g ai/ha the rate recommended for maize dissipated within 4 weeks for all species Wheat ryegrass carrot squash onions and tomato were not affected by topramezone residues from rates up to 202 g ai/ha in soil collected 2 weeks after treatment (WAT) However peas white clover and radish all suffered damage in samples collected 2 WAT By 4 WAT only white clover and peas exhibited minor phytotoxicity

Wandering Jew (Tradescantia fluminensis) prevents the regeneration of native forests in New Zealand The herbicide triclopyr effectively controls this weed but is damaging to many native plant species To identify alternative herbicides 16 active ingredients representing eight chemical groups were applied to containergrown wandering Jew plants of various ages in three experiments In Experiment 1 triclopyr killed all plants (3 months old) while amitrole caused substantial damage to plants In Experiment 2 amitrole terbuthylazine metsulfuronmethyl and triclopyr provided excellent control of 2 month old plants In Experiment 3 on 4 monthold plants wandering Jew was highly susceptible to triclopyr metsulfuronmethyl fluroxypyr glyphosate fluroxypyr metsulfuronmethyl triclopyr and picloram triclopyr These herbicides were evaluated in a subsequent field trial and all except metsulfuronmethyl gave similar levels of control to Experiment 3 Further investigation of these chemicals is required to determine their optimal use rates and safety for native plants

Abstract:We examined the applicability of the critical-source area (CSA) concept to the dairy-grazed 192-ha Upper Toenepi catchment and its 8Ð7-ha Kiwitahi sub-catchment, New Zealand. We evaluated if phosphorus (P) transport from land into stream is dominated by saturation-excess (SE) and infiltration-excess (IE) runoff during stormflow and by sub-surface (<1Ð5 m depth) flows during baseflow. We measured stream flow and shallow groundwater levels, collected monthly stream, tile drain (TDA) and groundwater samples, and flow-proportional stream samples from the Kiwitahi sub-catchment, and determined their dissolved reactive phosphorus (DRP) and total phosphorus (TP) concentrations. In the Kiwitahi sub-catchment, during storm events, IE contributions were significant. Contributions from SE appeared significant in the Upper Toenepi catchment. However, in both catchments, sub-surface contributions dominated stormflow and baseflow periods. Absence of water table at the surface and the water table gradient towards the stream indicated that P transport during events was not limited to surface runoff. The dynamics of the groundwater table and the occurrence of SE areas were influenced by proximity to the stream and hillslope positions. Baseflow accounted for 42% of the annual flow in the Kiwitahi sub-catchment, and contributed 37 and 52% to the DRP and TP loads, respectively. The P transport during baseflow appeared equally important as P losses from CSAs during stormflow. The close resemblance in P levels between groundwater and stream samples during baseflow demonstrates the importance of shallow groundwater for stream flow. In the Upper Toenepi catchment, contributions from effluent ponds (EFFs) dominated P loads. Management strategies should focus on controlling P release from EFFs, and on decreasing Olsen P concentrations in soil to minimize leaching of P via sub-surface flow to streams. Research is needed to quantify the role of sub-surface flow as well as to expand management strategies to minimize P transfers during stormflow and baseflow conditions.