Beneficial properties of weeds
Weed vegetation can have a neutral or positive effect on the functioning of agrocenoses. It serves as food for invertebrates, birds, and microorganisms, some of which destroy agricultural pests. For example, field bindweed (Convolvulus arvensis), when used correctly, helps preserve the symbiosis of beneficial mycorrhizae during winter.
The competent use of weed vegetation can protect soil from erosion, and some species are capable of fixing atmospheric nitrogen. They can be useful as fertilizers, feed, food products, dyes, or medicines (chamomile (Matricaria sp.), plantain (Plantago sp.), field horsetail (Equisetum arvense)). Ground-cover weeds — as mulch in fruit and berry plantings and vineyards. For example, goosefoot (Chenopodium sp.) and orache (Atriplex sp.), considered in modern agriculture as weeds, were grown as food sources before the crops introduced by Columbus from America. These plants were used as food during periods of mass famine in Russia, including during the Great Patriotic War of 1941–1945.
Chinese naturalists long ago observed the characteristics of weeds. They noticed that the appearance of certain plants in a specific place can be an indicator of underground deposits of zinc, selenium, nickel, or copper. By combining knowledge of mineralogy and botany, a discipline was created — geobotany.
Some weed species have ornamental value, such as poppy (Papaver sp.), chamomile (Matricaria sp.), cornflower (Centaurea sp.) and others, or are used as honey plants and attract pollinators.
In Great Britain, an attempt is being made to cultivate the weed field gromwell (Buglossoides arvensis) for the production of omega-3 fatty acids.
Useful weeds also include:
- sensitive plant (Mimosa pudica) — used as natural soil cover in tomato and pepper crops, attracts predatory insects;
- spurge vetch (Euphorbia lathyris) — repels moles;
- wild garlic (Allium vineale) — used in crops of fruit trees, nightshades (tomatoes, peppers, potatoes, etc.), crucifers (cabbage, broccoli, kohlrabi, etc.), carrots to repel slugs, aphids, and carrot fly;
- wild rose (Rosa sp.) — used as an ornamental shrub and medicine (fruits).
Habitat indicators
Many weed species are confined to certain field communities and soil habitat conditions. In the latter case, the reaction of weeds can be considered as an indication of natural edaphic conditions and as a response to soil properties, including those changed by agronomic measures.
The reaction of weeds to edaphic conditions is primarily manifested in responsiveness to moisture supply, soil reaction, and nutrient supply.
Indicator plants of soil water regime
With respect to the level of soil moisture, the following groups of weeds are distinguished:
- hygrophytes — occur exclusively on wet, poorly aerated soil: (marsh cudweed (Gnaphalium uliginosum), toad rush (Juncus bufonius), common windgrass (Apera spica-venti), field horsetail (Equisetum arvense), field mint (Mentha arvensis), marsh woundwort (Stachys palustris), creeping buttercup (Ranunculus repens));
- hygromesophytes — prefer moist, well-aerated soils (white goosefoot (Chenopodium album), many-seeded goosefoot (Lipandra polysperma formerly Chenopodium polyspermum), common fumitory (Fumaria officinalis), cleavers (Galium aparine), scentless mayweed (Tripleurospermum inodorum), field pennycress (Thlaspi arvense), field sowthistle (Sonchus arvensis));
- xerophytes — prefer well-aerated, warm, sometimes strongly drying soils (redroot pigweed (Amaranthus retroflexus), prostrate pigweed (Amaranthus blitoides), annual woundwort (Stachys annua), redstem stork's bill (Erodium cicutarium), bladder campion (Silene vulgaris), green foxtail (Setaria viridis), barnyardgrass (Echinochloa crus-galli), common ragweed (Ambrosia artemisiifolia)).
Indicator plants of soil acidity
According to their response to the pH of the soil solution (actual acidity), groups of indicator plants of soil acidity are distinguished:
- oxylophytes — grow mainly on soils with pH < 5.0 (sheep sorrel (Rumex acetosella), corn spurry (Spergula arvensis), annual knawel (Scleranthus annuus), field sandwort (Arenaria arvensis), scentless mayweed (Tripleurospermum inodorum), wild radish (Raphanus raphanistrum), common windgrass (Apera spica-venti), toad rush (Juncus bufonius));
- oxylomesophytes — grow on soils with a soil solution reaction from slightly acidic to neutral (wild oat (Avena fatua), spreading orache (Atriplex patula), treacle mustard (Erysimum cheiranthoides), field pennycress (Thlaspi arvense), black henbane (Hyoscyamus niger), marsh woundwort (Stachys palustris), silverweed (Argentina anserina formerly goose cinquefoil, Potentilla anserina), field sowthistle (Sonchus arvensis));
- plants indifferent to soil solution reaction (white goosefoot (Chenopodium album), shepherd's purse (Capsella bursa-pastoris), corn cockle (Agrostemma githago), Canadian horseweed (Erigeron canadensis), large-flowered hemp-nettle (Galeopsis speciosa), common yarrow (Achillea millefolium)).
The presence of several weed species of one group provides grounds for assessing the advisability of liming soils. This practice often leads to a change in the floristic composition of weeds and reduces crop infestation.
Indicator plants of nutrient regime
According to the level of responsiveness to the soil supply of mineral nutrients (nutrient regime), "element-positive" and "element-negative" groups of weeds are distinguished. In agricultural practice, it is important to know the indicator plants that respond positively to a high content of certain mineral nutrients in the soil.
The group of nitrophiles (nitrogen-loving) includes white goosefoot (Chenopodium album), many-seeded goosefoot (Lipandra polysperma formerly Chenopodium polyspermum), spreading orache (Atriplex patula), wild radish (Raphanus raphanistrum), field mustard (Sinapis arvensis), pale persicaria (Persicaria lapathifolia), large-flowered hemp-nettle (Galeopsis speciosa), bifid hemp-nettle (Galeopsis bifida), barnyardgrass (Echinochloa crus-galli), annual bluegrass (Poa annua), sheep sorrel (Rumex acetosella).
Phosphatophiles include: common groundsel (Senecio vulgaris), field pansy (Viola arvensis), corn spurry (Spergula arvensis), red sandspurry (Spergularia rubra), common fumitory (Fumaria officinalis), henbit deadnettle (Lamium amplexicaule).
Kaliphiles include cleavers (Galium aparine), spreading orache (Atriplex patula), field pennycress (Thlaspi arvense), field sowthistle (Sonchus arvensis).
The above classification of weeds in relation to various mineral nutrients is not absolute, since as mineral nutrition changes, other living conditions also change. Therefore, the response of weeds to individual elements may also change.
References
- Bazdyrev G. I., Loshakov V. G., Puponin A. I. et al. (2000). Agriculture. Textbook for universities. Moscow: Kolos Publishing House.
