Effect of nitrogen rates and weed control methods on weeds abundance and yield of direct-seeded rice

Field experiments were conducted at the Punjab Agricultural University, Ludhiana, India, during 2007-2008 to examine if nitrogen (N) rates and weed management practices using herbicides in combination with hand-weeding (HW) can improve crop competitiveness against weeds, and increase the yield, water productivity and profitability of direct-seeded rice (DSR). Increasing N application rate up to 150 kg ha caused significant improvement in grain yield when the weeds were well controlled either by Pendimethalin + Bispyribac Na or by Pendimethalin + Bispyribac Na + 1 HW, respectively; however, under poor weed control condition (Pendimethalin + 1 HW), it resulted in a drastic reduction in yield. The highest net returns ($1083) and water productivity (0.60 kg m) were observed for N application of 150 kg ha and weeds were controlled with Pendimethain + Bispyribac Na + 1 HW. We suggest that Pendimethalin + Bispyribac Na + 1 HW is the best integrated weed management strategy to control weeds, and to increase yield, water productivity, and profitability. We propose that the simulation modelling tool be utilized in future for evaluating options for improving sustainable N and weed management policies especially when crop, weeds, soil, weather and management data are available for calibration and validation of appropriate and existing simulation model of rice

Response of Greenhouse tomato to irrigation and fertigation

A 2-year study was conducted during 2002-2004 at Department of Soil and Water Engineering, Punjab Agricultural University, Ludhiana to investigate the effect of irrigation and fertigation on Greenhouse tomato. Drip irrigation at 0.5 × E along with fertigation of 100% recommended nitrogen resulted an increase in fruit yield by 59.5% over control (recommended practices) inside the Greenhouse and by 116.2% over control (recommended practices) outside the Greenhouse, respectively. The drip irrigation at 0.5 × E irrespective of fertigation treatments giving a saving of 48.1% of irrigation water and resulted in 51.7% higher fruit yield as compared to recommended practices inside the Greenhouse. Total root length was more in drip irrigated crop as compared to surface irrigated crop. Greenhouse tomato fruits founded superior than fruits of open field crop in view of fruit size, TSS content, ascorbic acid content and pH. Further, drip irrigation in Greenhouse crop caused significantly improvement in all the quality characteristics

Glyphosate Efficacy in <i>Chloris virgata</i> Sw. in Response to Temperature and Tank Mixing

Glyphosate alone or a tank mixture of glyphosate and 2,4-D is commonly used for broad-spectrum weed control under fallow conditions in Australia. Air temperature or mixing glyphosate with 2,4-D, may influence the efficacy of glyphosate on feather fingergrass (Chloris virgata Sw.), a problematic summer-season weed of Australia. Dose–response studies were conducted with four populations of feather fingergrass under temperature-controlled glasshouse conditions (35/25 °C and 25/15 °C at 12 h/12 h) to assess the level of glyphosate resistance in relation to temperature regimes. Four parameter log-logistic models were used to develop dose–response curves. Based on plant mortality percentage, LD50 (lethal dose for 50% mortality) values of glyphosate at 25/15 °C for populations Ch, SGM2, SGW2, and CP2 were 137, 60, 650, and 1067 g ae ha−1, respectively. However, at 35/25 °C, the corresponding LD50 values were 209, 557, 2108, and 2554 g ae ha−1, respectively. A similar response was observed for the parameter GR50 (dose for 50% growth reduction) values of glyphosate. These results indicate that populations SGW2 and CP2 are highly glyphosate-resistant and in the summer season, it may be very difficult to control these populations due to poor glyphosate efficacy. These results further suggest that the efficacy of glyphosate for feather fingergrass control can be improved if applied during cooler temperatures (25/15 °C) or the spring season compared with warmer temperatures (35/25 °C) or the summer season. In another study, 2,4-D antagonized glyphosate remarkably in the CP2 (glyphosate-resistant) population but only marginally in the Ch (glyphosate-susceptible) population. Thus, it is not advisable to mix 2,4-D with glyphosate for the control of glyphosate-resistant feather fingergrass populations. The results further suggest that the use of this mixture is useful if the feather fingergrass is not glyphosate-resistant; however, the use of the mixture is to be avoided if the population is glyphosate-resistant in order to not exacerbate the potential resistance problem

Effects of planting pattern and cultivar on weed and crop growth in aerobic rice system

Weeds are a major biotic constraint to aerobic rice production in Asia. Research is needed on the effects of cultural practices on weed management in aerobic rice, including techniques such as planting pattern and competitive cultivars. Field experiments were conducted in Punjab, India, in the wet seasons of 2008 and 2009 to study the growth of weeds and two rice cultivars [PR 115 and Punjab (P.) Mehak 1] in relation to planting pattern (uniform rows [23-cm row spacing] and paired rows [15-, 30-, and 15-cm row spacings]) under aerobic conditions. Junglerice and rice flatsedge were the dominant weed species during the early stages of the crop, while Chinese sprangletop and large crabgrass were the predominant species during flowering stage of the crop. Weed dry matter was not affected by planting pattern of P. Mehak 1; however, for PR 115, weed dry matter was greater in rice grown in uniform rows (244 g m -2) than in paired rows (183 g m -2). Planting patterns did not affect weed-free crop growth and yield, but weeds tended to be more abundant in the uniform planting system, particularly under cultivar PR 115. Consequently, this cultivar grew and yielded better under the paired rows when weeds were present. The cultivar PR 115 had greater yield potential than P. Mehak 1, but growth and productivity of P. Mehak 1 were unaffected by the planting patterns, suggesting better competitive ability against weeds than PR 115. The results imply that yield of some aerobic rice cultivars may be improved by exploring competitiveness of rice cultivars through paired row planting patterns. There is a need to study plasticity changes for cultivars which respond with more competiveness in paired rows. The identified traits could be useful as selection criteria for screening weed-competitive cultivars in paired row pattern

Screening of Herbicides for Rice Seedling Safety and Echinochloa colona Management under Australian Conditions

Different herbicides are currently required for sustainable weed management in aerobic rice. Three pot experiments were conducted using different herbicides to evaluate rice safety and for the control of Echinochloa colona, a major weed of aerobic rice. Among the pre-emergence (PRE) herbicides, it was found that pendimethalin (594 g ai ha&minus;1) and flumioxazin (60 g ai ha&minus;1) were relatively safe herbicides for rice and provided 100% control of E. colona. All other PRE herbicides, such as atrazine, cinmethylin, clomazone, dimethenamid-P, isoxaflutole, metribuzin, prosulfocarb + S-metolachlor, pyroxasulfone, trifluralin, and S-metolachlor reduced the biomass of rice compared with the non-treated control. Dose-response studies revealed that flumioxazin and pendimethalin even at low doses (30 g ai ha&minus;1 for flumioxazin and 294 g ai ha&minus;1 for pendimethalin) provided excellent control (&gt;95%) of E. colona. Post-emergence (POST) application of paraquat (360 g ai ha&minus;1) at the time of rice emergence caused toxicity in the crop, but also provided excellent control of E. colona. When applied just after crop emergence (11 days after sowing), Pendimethalin was found to be safe for rice (2% mortality) and reduced the biomass of E. colona by 88% compared with the non-treated control. It is quite possible that the rice variety Reiziq used in this study may have a tolerance to flumioxazin, which needs further investigation involving more rice varieties. This study suggests that flumioxazin can be used as an alternative to pendimethalin for the sustainable management of E. colona in aerobic rice