Comparison of Weed Seedbanks in Different Rice Planting Systems

Abstract

Core Ideas Weed seedbanks were compared in three rice planting systems: machine‐transplanted rice, water direct‐seeded rice, and dry direct‐seeded rice. Weed seedbanks were mainly distributed in soil within a depth of 10 cm. Dry direct‐seeded rice tended to maintain larger seedbanks of sedges, grasses, and some upland weeds. Water direct‐seeded rice contained the smallest weed seedbank overall. Machine‐transplanted rice had larger seedbanks of broadleaf weeds and some traditional rice weeds. Machine‐transplanted rice (Oryza sativa L.) (MTR), water direct‐seeded rice (WDSR), and dry direct‐seeded rice (DDSR) are three important alternatives to traditional manual transplantation of rice. Weed infestation is a pervasive problem in all rice planting systems. The weed seedbanks under different rice planting systems have seldom been compared. Thus, we sampled weed seeds in fields employing MTR, WDSR, and DDSR consecutively for at least 5 yr in Wujin County, eastern China. Seeds of 26 companion weed species of rice, comprising 16 families, were observed. Most weed seeds, 82.5% in MTR, 75.3% in WDSR, and 81.7% in DDSR, were distributed in soil 0‐ to 10‐cm deep. As soil depth increased, the seedbanks of total weeds, broadleaf weeds, grasses, and sedges all significantly decreased under the different rice planting systems, except for sedges under WDSR. The DDSR tended to maintain larger seedbanks of sedges and grasses, as well as some upland weeds, such as Digitaria sanguinalis (L.) Scop. and Eleusine indica Gaertn. The WDSR system contained the smallest weed seedbank overall but tended to have larger seedbanks of several weeds, such as Ammannia arenaria H. B. K. and Lindernia procumbens (Krock.) Philcox. Weedy rice and Cyperus difformis L. tended to maintain larger seedbanks in DSR fields. The MTR fields tended to have larger seedbanks of broadleaf weeds and some traditional rice weeds, with significantly lower richness of weed species in the seedbank. Therefore, to downsize the weed seedbank, WDSR or MTR should be employed rather than DDSR when possible. Moreover, the influences rotation of different rice planting systems on the weed seedbank merit more studies.

Paddy Crop and Weed Discrimination: A Multiple Classifier System Approach

“…e result in Table 9 shows that the feature set extracted has the potential for effective feature vector representation of paddy crop and weed images for the classification process. (11) for i ⟵ 1 to n do (12) Train C i on Train set-1 (13) end for (14) for i ⟵ 1 to len do (15) p Predict probability of classes for sample S i using C1, where S i Є Test-set ( 16) q Predict probability of classes for sample S i using C2, where S i Є Test-set (17) end for (18) for i ⟵ 1 to len do (19)…”

“…end if (34) if q[i][j] > max2 then (35) max2 q[i][j] (36) index2 j (37) end if (38) end for (39) (11) for i ⟵ 1 to n do (12) Fit calibrated C i using isotonic regression on Train set-1 (13) end for (14) for i ⟵ 1 to len do (15) p Predict probability of classes for sample S i using C1, where S i Є Test-set (16) q Predict probability of classes for sample S i using C2, where S i Є Test-set (17) end for (18) for i ⟵ 1 to len do (19)…”

“…It is reported that annually India is incurring a loss of INR 1050 million because of weeds in paddy fields [14]. Classification of weeds in rice fields is usually based on their life cycle, their habitat, and their gross morphological features [15]. ey are broadly categorized as sedges, grass, and broadleaved weed [16], as shown in Figures 1(a)-1(c), respectively [17,18].…”

Environmental factors on seed germination and seedling emergence of Phleum paniculatum Huds.

“…Phleum paniculatum seed is quite small, with a thousand-seed weight of only 0.17 to 0.23 g. Small seeds have limited nutritional storage and sustaining extensive seedling growth from germination stage to emergence may be the reason that seedling emergence of P. paniculatum is more sensitive to soil burial depth than other weed species (Baskin and Baskin, 1998). Many studies have reported that zero-tillage and reduced tillage often facilitate the seriousness of weed occurrence in croplands (Thomas et al, 2004;Chauhan and Johnson, 2009;Chen et al, 2017). In China, farmers either till lands to a depth of less 5 cm before seeding wheat or do not till the soil at all.…”

Early agriculture in Sri Lanka: New Archaeobotanical analyses and radiocarbon dates from the early historic sites of Kirinda and Kantharodai (Kandarodai)

“…and the small, elongate Digitaria sp.. Digitaria spp. are widespread weeds, both of rice and millet cultivation(Chen et al 2017;Moody 1989). While kodo millet (Paspalum scorbiculatum)was an important cultivar in Iron Age and Early Historic southern India(Cooke and Fuller 2015).…”