Field experiments were conducted during the winters of 1986–87 and 1987–88 at Haryana Agricultural University, Hisar, India to classify the ability of winter wheat cultivars to compete with wild oat. Wild oat reduced winter wheat grain yield by 17 to 62% depending upon cultivar. WH-147 and HD-2285 were the most competitive cultivars. Winter wheat dry matter accumulation and grain yield were negatively correlated with wild oat dry matter. A high number of tillers, particularly in HD-2009, WH-291, and S-308, did not always translate into grain yield advantage in wild oat-infested plots. Wheat height and dry matter accumulation per unit area during early crop growth were better characters than number of tillers for predicting the competitive ability of wheat cultivars to wild oat.

Field experiments were conducted to evaluate control of 90- to 100-cm-tall ragweed parthenium in a noncropped situation in Haryana State, India, during 2000 and 2001. Atrazine, 2,4-D ethyl ester, atrazine plus 2,4-D, metribuzin, metsulfuron, chlorimuron, glufosinate with and without surfactant, glyphosate with and without surfactant, and glyphosate formulations MON 8793 and 8794 were sprayed on ragweed parthenium. Also, the effect of water quality was studied with flat-fan and flood-fan nozzles using glyphosate and its formulation MON 8793 against ragweed parthenium and associated weeds. Glyphosate MON 8793 and 8794 at 3.6 kg ae/ha provided excellent control of ragweed parthenium followed by glyphosate at 2.7 or 5.4 kg/ha, with no recovery until 18 wk after treatment (WAT). Addition of 0.1% v/v surfactant (MON 0818) to glyphosate at 2.7 kg/ha provided similar control to that of glyphosate alone at 5.4 kg/ha. Other herbicides failed to provide satisfactory control of ragweed parthenium. In the water quality study, glyphosate at 2.7 and 5.4 kg/ha and glyphosate MON 8793 at 2.7 and 3.6 kg/ha provided similar control of ragweed parthenium at 18 WAT. Glyphosate was antagonized less by tap water (0.45 mM Ca) than canal (0.7 mM Ca) and hand-pump water (1 mM Ca). Neither glyphosate nor glyphosate MON 8793 provided good control of purple nutsedge, velvetleaf, garden spurge, threelobe false mallow, jimsonweed, giant milkweed, Indian jujube, or tropical spiderwort, but crowfootgrass, green foxtail, sprawling signalgrass, and spiny amaranth were controlled. Glyphosate at 5.4 kg/ha and glyphosate MON 8793 at 3.6 kg/ha provided more than 80% control of bermudagrass at 8 WAT, which was significantly better than the 2.7 kg/ha rate. Flat-fan nozzles provided better efficacy of applied herbicides than flood-fan nozzles at 4 WAT on ragweed parthenium.

The effect of environmental conditions on horse purslane (Trianthema portulacastrum L. # TRTPO) emergence, growth, and reproduction was studied by sowing seeds on June 10, June 30, July 20, August 10, and August 30, 1984. The first three seeding dates resulted in significantly higher seedling emergence than the August 30 date. Leaf number, leaf area, dry matter, and number of branches per plant at the peak growth stages of this weed were significantly higher for the July 20 sowing than for the other sowing dates, followed closely by the June 30 sowing. Similarly, number of nodes per plant, seeds per plant, and seed weight per plant were also significantly higher for the July 20 sowing, followed closely by the June 30 sowing. Phenological behavior of the plants indicate that: a) maximum seedling emergence takes place during June and July, b) rapid and vigorous growth occurs during July and August (rainy season) when conditions for growth are optimum, and c) production of flowers and seeds starts 20 to 30 days after sowing.

Horse purslane (Trianthema portulacastrum L. # TRTPO) seeds germinated from 20 to 45 C. Maximum germination of 90% was observed at 35 C. Germination was highest between the 4th and 8th days of incubation. Horse purslane seeds did not exhibit dormancy. Freshly harvested seeds when incubated at 35 C germinated to the extent of 54 to 56%. Seed germination steadily increased up to 7 and 8 months when stored under laboratory and field conditions, respectively. Seeds stored in soil had significantly higher germination than those stored in the laboratory. Maximum seedling emergence resulted when seeds were planted at 1 cm and gradually declined with the increased seeding depth. Seeds lying on the surface gave very poor seedling emergence.

Two field experiments were carried out from 1993 to 1995 to evaluate the critical period of weed control and to develop suitable weed management practices for jungle rice, horse purslane, and cockscomb in soybean. Horse purslane was more competitive during early growth stages (up to 45 days after sowing [DAS]) and cockscomb was more competitive during later growth stages, whereas jungle rice was competitive throughout the growing season. The critical period of weed control was found to be 30 to 45 DAS. Weed-free maintenance up to 45 DAS resulted in a 74% increase in grain yield of soybean over the unweeded control. Keeping soybean weed free for 45 d or allowing weeds to remain in the crop for less than 30 d resulted in no significant yield loss. Sequential application of a reduced rate of soil-applied trifluralin 1.0 kg ha–1(0.67 ×) with postemergence fluazifop 0.75 kg ha–1(0.75 ×) or a reduced rate of soil-applied trifluralin or pendimethalin at 1.0 kg ha–1(0.67 ×) followed by hand hoeing 35 DAS provided better control of a broad spectrum of weeds than a single application of a postemergence herbicide applied at reduced or recommended rates. Integration of reduced rates of soil-applied herbicides with post-emergence herbicides or hand hoeing 35 DAS produced soybean yields similar to the hand-weeded treatment. Compared to the weed-free or integrated weed control, a single application of soil-applied or postemergence herbicide did not control a broad spectrum of weeds and reduced soybean yield.