Weed emergence and seedbank after three years of repetitive shallow cultivation in a muck soil field

Frequent cultivation is often used to control weeds in crops such as lettuce. The efficacy of this technique on weed populations has been evaluated, but the effect on weed emergence and seedbanks is less documented. Studies in mineral soil indicate that soil disturbance can increase both weed emergence and seed persistence depending on where seeds are redistributed in the soil profile. Evaluations done in muck soil are scarce. This study evaluated the effect of two and four repetitive shallow (3.4 to 7.1 cm deep) cultivations on weed emergence and the weed seedbank in muck soil. Cultivation treatments (0, 2 and 4 cultivations using a inter-row rototiller) were done in lettuce plots from 2017 to 2019. Weed density was evaluated by species before each cultivation date and after crop harvest. Viable seedbanks were evaluated by collecting soil samples before and after each growing season and placing them in greenhouse flats. Statistical analyses were based on mixed models. Results showed that shallow cultivation modified the emergence patterns of weeds but did not reduce total emergence during the subsequent years or viable seedbanks. After two seasons without seed inputs, total emergence was reduced by 46.6% and the seedbank was reduced by 31.7% regardless of the cultivation treatment. However, the seedbank of the very abundant common purslane (<i>Portulaca oleracea</i>) remained high.

Bioherbicidal Actions of Common Purslane on Seed Germination and Growth of Some Crop and Weed Species

This study was conducted to examine allelopathic actions of Common Purslane Portulaca oleracea L. aqueous shoot and root extracts on germination of seeds and some growth parameters of wheat (Triticum aestivum) and rapeseed (Brassica napus). The experiment was performed in sterilized Petri dishes for one week at 22 °C. The experiment was arranged for completely randomized design. The concentrations were chosen for this study as (0%, 3%, 6% and 9%). The results indicated that the higher concentrations (6% and 9%) of both shoot and root extracts of common purslane caused significant reduction in seed germination whereas the lowest concentration caused the least negative impact on seed germination. Other growth polarimeters such as shoot and root length and shoot and root oven dry weight were significantly inhibited by the application of both Common Purslane aqueous shoot and root extracts at concentrations (6% and 9%) in wheat T. aestivum and rapeseed B. napus. However, dicot B. napus turned out to be more effected than monocot T. aestivum. The findings of this study suggest that common purslane aqueous shoot and root extracts can be recommended to utilize as bio-herbicide to supress seed germination and growth of weeds.

Significance of herbicide order in sequential applications to target weeds in a sunn hemp living mulch

Striking a balance between the weed control capacity of living mulches and their competition with the main crop is complex. At rates that avoid severe injury to living mulch, herbicides may reduce their vigor while simultaneously contributing towards weed control. In a two-year field study carried out in Freeville, NY, USA, we evaluated the effects of various combinations consisting of two herbicides, applied sequentially at reduced rates, on the growth of a sunn hemp living mulch and weeds (including common lambsquarters, common purslane, hairy galinsoga, and Powell amaranth). When a herbicide with primarily POST activity (Type 1) (e.g., rimsulfuron, 0.005 to 0.007 kg ai ha-1) was applied first, performance of sunn hemp (1.7 to 3.9 tons ha-1 dry biomass; 10 to 88% groundcover) was poor and weed growth (25 to 62% groundcover) was high, likely because sunn hemp, severely injured at a young growth stage, was outcompeted by weeds. A follow-up application (approximately two weeks later) of a herbicide with primarily PRE and residual activities (Type 2) (e.g., metribuzin, 0.05 to 0.15 kg ai ha-1), with a surfactant to enhance its POST activity, had little effect on established weeds. However, because sunn hemp was already 20 cm tall at weed emergence, applying a Type 2 herbicide first, did not cause severe injury to sunn hemp and reduced weed pressure, thereby also enhancing sunn hemp performance (3.8 to 6.1 tons ha-1 dry biomass; 85 to 94% groundcover). Moreover, the follow-up application of a Type 1 herbicide affected the smaller weeds more (4 to 21% groundcover) than the better-established sunn hemp. Our results demonstrate that an appropriate sequence of herbicides at reduced rates may be important to control weeds while maintaining a healthy living mulch stand.

Plant use in Muslim Spain: Preliminary results from the medieval town of Madīnat Ilbīra

The paper presents preliminary results of archaeobotanical studies carried out at the Madīnat Ilbīra site in Spain. The functioning of the town, which was the capital of one of the administrative districts (kūras) of al- Andalus, falls in the period between the second half of the 9th century and the 11th century. However, the analysed soil samples were collected from archaeological contexts dated mostly to the last decades of the 10th century and to the 11th century. The samples yielded an interesting set of data about the preserved plant remains. Although the taxonomic diversity of the plants is not high, the analysis revealed remains of naked and hulled wheat (emmer wheat), millet, poppy seeds, perhaps peas, cucumber or melon, and grapevine. Although crop plants played an important role in the everyday diet of the town inhabitants, wild plants also were probably collected and used. The latter are represented in the analysed materials by, for example, wild strawberry, common mallow and common purslane. The preserved charcoal remains confirm the use of different species of wood as fuel.

Interaction of Common Purslane (Portulaca oleracea) and Palmer amaranth (Amaranthus palmeri) with Sweetpotato (Ipomoea batatas) Genotypes

Greenhouse replacement series studies were conducted to determine the relative competitiveness of NC10-275 (unreleased, drought tolerant; upright, bushy, and vining growth with large leaves) and Covington (most commonly grown genotype in North Carolina; vining growth with smaller leaves) sweetpotato genotypes with weeds. Sweetpotato genotypes were grown with Palmer amaranth (tall growing) or common purslane (low growing) at five planting (sweetpotato:weed) proportions of 100:0, 75:25, 50:50, 25:75, and 0:100% at density of four plants pot-1. Reduction in common purslane shoot dry biomass was greater when growing with NC10-275 than when growing with Covington or alone. When growing with common purslane, shoot dry and root fresh biomass of Covington was 18 and 26% lower, respectively, than NC10-275. Relative yield (shoot dry biomass) and aggressivity index (AI) of common purslane was lower than both sweetpotato genotypes. Palmer amaranth shoot dry biomass was similar when growing alone or with Covington; whereas, it was reduced by 10% when growing with NC10-275 than alone. Palmer amaranth competition reduced shoot dry biomass and root fresh biomass of Covington by 23 and 42%, respectively, relative to NC10-275. Relative yield and AI of Palmer amaranth was greater than Covington but lower than NC10-275. This research indicates that sweetpotato genotypes differ in their ability to compete with weeds. Both sweetpotato genotypes were more competitive than common purslane, and the following species hierarchy exists: NC10-275 > Covington > common purslane. In contrast, NC10-275 was more competitive than Covington with Palmer amaranth, and the following species hierarchy exists: NC10-275 ≥ Palmer amaranth>Covington.

Suppression of Weed Occurrence in a Five-year Corn-earthworm Coculture System

The use of a corn-earthworm coculture (CE) system is an eco-agricultural technology that has been gradually extended due to its high economic output and diverse ecological benefits for urban agriculture in China. However, the effect of CE on weed occurrence has received little attention. A five-year successive experiment (2015 to 2019) was conducted to compare weed occurrence in CE and a corn (Zea mays L.) monoculture (CM). The results show that CE significantly decreased weed diversity, the dominance index, total weed density and biomass, but increased the weed evenness index. The five-year mean number of weed species per plot was 8.4 in CE and 10.7 in CM. Compared to those in CM, the five-year mean density and biomass of total weeds in CE decreased by 59.2% and 66.6%, respectively. The effect of CE on weed occurrence was species specific. The mean density of large crabgrass [Digitaria sanguinalis (L.) Scop.], green foxtail [Setaria viridis (L.) Beauv.], goosegrass [Eleusine indica (L.) Gaertn.], and common purslane (Portulaca oleracea L.) in CE decreased by 94.5, 78.1, 75.0, and 45.8%, whereas the mean biomass decreased by 96.2, 80.8, 76.9, and 41.4%, respectively. Our study suggests that the use of CE could suppress weed occurrence and reduce herbicide inputs in agriculture.

Phytotoxic Activity of the Natural Compound Norharmane on Crops, Weeds and Model Plants

Norharmane is a secondary metabolite that appears in different species of land plants. In this paper, we investigated for the first time the specificity of norharmane through germination and growth tests on some crops as Zea mays L. (maize), Triticum aestivum L. (wheat), Oryza sativa L. (rice) and Lactuca sativa L. (lettuce) and weeds as Amaranthus retroflexus L. (amaranth), Echinochloa crus-galli L. (barnyard grass), Plantago lanceolata L. (ribwort), Portulaca oleracea L. (common purslane) and Avena fatua L. (wild oat), and its phytotoxic capacity on the metabolism of adult Arabidopsis thaliana L. (thale cress) by measuring chlorophyll a fluorescence, pigment content, total proteins, osmotic potential and morphological analysis. Norharmane had an inhibitory effect on the germination of A. fatua and P. lanceolata, and the growth of P. oleracea, E. crus-galli and A. retroflexus. On adult A. thaliana plants, the compound was more effective to watering, leading to water stress that compromised the growth of the plants and ultimately affected the photosynthetic apparatus. Therefore, this research shows that norharmane not only affects seedlings’ metabolism, but also damages the metabolism of adult plants and can be a potential model for a future bioherbicide given its specificity.