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The use of carbonized
rice husk biochar improves the fertility and productivity of poor soils in
rice-based cropping systems. However, biochar may also influence weed seedling
emergence and the efficacy of soil-applied herbicides. Experiments were
conducted in a screenhouse to evaluate the effect of biochar rates (0, 20, 40,
and 80 t·ha?1)
and seed burial depth (0, 1, and 2 cm)
on seedling emergence of junglerice (Echinochloa
colona) and the effect of biochar rates and pendimethalin (0, 500, 1000,
and 1500 g·a.i.·ha?1) and pretilachlor doses (0, 300, 600,
and 900 g·a.i.·ha?1) on seedling emergence and seedling
biomass of junglerice. Data were analyzed using nonlinear regression. The
burial depth to inhibit 50% of maximum seedling emergence was 0.76 cm when biochar was not added to soil
and the depth increased with an increase in biochar rates for soil. Similarly,
compared with the soil with no biochar, the use of bichoar increased the
pretilachlor dose to inhibit 50% of maximum emergence or biomass. The
pretilachlor dose to inhibit 50% of maximum biomass of junglerice was 100, 130,
A study was
conducted in a split-plot design to evaluate the effect of fertilizer placement
method on weed growth and grain yield in a dry-seeded rice (DSR) system.
Main-plot treatments were four fertilizer placement methods: between narrow
rows (between 15-cm-wide rows of the pattern 25-15-25 cm), between uniform rows
(between 20-cm-wide rows), within uniform rows, and surface broadcast. Subplot
treatments were three weed control methods: herbicide-treated, nontreated, and
weed-free. Weed biomass was greater in the nontreated plots than in the
herbicide-treated plots. Herbicide application reduced weed biomass by 89% to 99% compared with the
nontreated control. Fertilizer placement did not influence weed biomass in the
herbicide-treated plots; however, it greatly influenced biomass in the
nontreated plots. Fertilizer placement on the surface increased weed biomass (69 -71 g·m–2)
compared with the placement of fertilizer below the soil surface (37 -57 g·m–2).
Fertilizer placement did not influence weed density and biomass at 60
days after planting. Nontreated plots yielded 700 to 2080 kg·ha–1.
Grain yield was similar between the herbicide-treated (2660-3250 kg
Drought is the most important abiotic
constraint in rainfed rice systems. In these systems, Amaranthus spinosus and Leptochloa chinensis are the dominant weed
species, which may reduce the available water to rice by competition and cause
water stress in the crop. Two studies were conducted in a greenhouse to evaluate
the growth response of A. spinosus and rice and L. chinensis and rice to water stress.
The water stress treatments were 12.5%, 25%, 50%, 75%, and 100% of field
capacity and the plants were grown until weed maturity (i.e., 63 days from seeding). Rice plants did not survive at 12.5% and 25% of field
capacity, but both weed species survived in all the treatments. Both weed
species produced a significant
cropping system is increasing in Asia in response to increased demand of corn
for feed. A field study was conducted to evaluate the effect of plant geometry
(row and plant to plant spacing: 50 × 20, 50 × 30, 75 × 20, and 75 × 30 cm) on
growth and yield of corn. Plant height and leaf production per plant were not
influenced by the plant geometry. Spacing, however, influenced
leaf area, aboveground shoot biomass, and yield of corn per unit area. Highest
leaf area, shoot biomass, and yield (8.2 t·ha-1) were produced by plants grown
at 50 × 20 cm spacing. The results of this study suggest that narrow rows and
plant to plant spacing may increase grain yield by increasing crop growth
rates. Plant geometry could be modified to improve yield of corn in the
rice-corn cropping system, and thereby increase productivity of the system.
Philippines, rice monoculture systems are common. Compared to these systems, the
rice-soybean cropping system may prove more water-efficient and there is a trend of increasing soybean
area in the response to water scarcity and need for crop diversification in the
Philippines. A field study was conducted to evaluate the effect of row and
plant to plant spacing (20 × 10, 20 × 5, 40 × 10, and 40 × 5 cm) on growth and
yield of soybean. Plant height was not influenced by the plant
geometry. Spacing, however, influenced leaf area and shoot biomass of soybean.
Plants grown at the widest spacing (i.e.,
40 × 10 cm) produced lowest leaf area and shoot biomass at 6 and 12 weeks after
planting. Leaf area and shoot biomass at other three spacing were similar.
There was a negative and linear relationship between weed biomass and crop
shoot biomass at 6 and 12 weeks after planting. Grain yield of soybean was not
affected by plant geometry and it ranged from 1.3 to 1.9 t·ha-1 at different spacing.
The demand for corn is increasing in Asia for feed and biofuel. It is grown in the rice-corn cropping system. During harvest of corn, however, seeds drop on the soil surface and become problems as volunteer corn seedlings in the subsequent dry-seeded rice crop, in which the suppressive effect of standing water is absent. A study was conducted in screenhouse and field conditions to evaluate the effect of rice herbicides on the management of volunteer corn seedlings. In the screenhouse experiment, bispyribac-sodium at 0.030 and 0.045 kg·ai·ha-1 provided complete control of corn seedlings. Fenoxaprop + ethoxysulfuron and penoxsulam + cyhalofop did not provide effective control of corn seedlings. In the field, the sole application of bispyribac and sequential application of oxadiazon and bispyribac suppressed corn biomass by 60%-82% and 89%-91%, respectively, as compared with the nontreated control. The results of this study demonstrate that, in the absence of other management strategies, volunteer corn seedlings in dry-seeded rice systems can be managed by using bispyribac-sodium.
A study was undertaken in February 2012 to understand the knowledge and practices of rice farmers about weedy rice in two municipalities of Iloilo, Philippines. The specific objectives of the study were to establish what rice farmers know about weedy rice, examine rice farmers’ practices in managing weedy rice, and recommend policies on weedy rice management based on the results of the study. Farmers’ knowledge of weedy rice did not differ much between two villages. Results showed that 41% from the second most affected village and 33% from the most affected village thought that weedy rice cannot reduce the market value of the harvested rice. Majority of the farmers (68%) responded that awns can be absent in some weedy rice and about 40% of the farmers did not know that seeds of weedy rice have dormancy. Cutting the weedy rice panicles at harvest, as the best way of reducing weedy rice, was practiced by majority of the respondents (82%) from the most affected village. Our study suggests that there is a need to increase awareness about weedy rice among Asian farmers.