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Not AvailableAbstract Field experiments were conducted to study the effect of irrigation and nitrogen levels on radiation use efficiency (RUE), radiation extinction coefficient (j) and temporal variation of leaf area index (LAI) and fraction intercepted photosynthetically active radiation (fIPAR). The LAI of wheat increased with increase in irrigation and nitrogen levels. The fIPAR also followed trend similar to LAI. The LAI and fIPAR showed logarithmic relationship with R2 value of 0.92 and 0.93 for the years 2013–2014 and 2014–2015, respectively. The j value varied between 0.41 and 0.78 and was significantly affected by nitrogen levels but was not influenced by irrigation levels. The grain and above ground biomass (AGB) yields of wheat were not affected significantly by irrigation levels. However, application of 160 kg N ha-1 (N160) registered higher grain (12–33%) and AGB (22–25%) yeilds as compared to that with application of 40 kg N ha-1 (N40). Similar to AGB, the total intercepted photosynthetically active radiation (TIPAR) was not affected by irrigation levels but N160 treatment registered 9–20% higher TIPAR compared to N40 treatment. The linear relationship between TIPAR and AGB revealed that 83–86% variation in AGB yield of wheat can be explained by TIfIPAR. The RUE of wheat under three irrigations (I3) was 6 and 18% higher (P\ 0.05) than the five (I5) and two (I2) irrigation treatments, respectively for the year 2013–2014. However, there was no significant effect of irrigation on RUE of wheat in the year 2014–2015. N160 treatment registered 5–13% higher RUE than the N40 treatment. Thus wheat may be grown with three irrigations (CRI, flowering and grain filling) and 160 kg N ha-1 for higher RUE without significant reduction in AGB of wheat compared to five irrigation levels in semi-arid location of Delhi region.Not Availabl

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Not AvailableThe best and commonly used ground - based sensor to monitor crop growth, ASD FieldSpecPro Spectroradiometer (Analytical Spectral Devices, Boulder, CO, USA) is a passive sensor, which can be used under adequate light condition. However, now - a - days active sensors such as GreenSeekerTM (GS) handheld crop response (Trimble Agriculture division, USA) are used for monitoring crop growth and are flexible in terms of timeliness and illumination conditions besides being cheaper than the ASD. Before its wide use, the suitability and accuracy of GS should be assessed by comparing the NDVI measured by this instrument with that by ASD, under diverse wheat growing conditions of India. Keeping this in view, the present experiment was undertaken with the following objectives: (1) to find out the temporal variation of NDVI measured both by ASD and GS treatments, (2) to find out relationship between the NDVI measured through ASD and GS and, (3) to evaluate the suitability of GS for NDVI measurements. It was observedthatthe numerical value of NDVI as measured by GS was always significantly (P \ 0.05) lower than that measured by ASD for all the experiments under study. The NDVI - ASD and NDVIGS were significantly positively correlated (P \ 0.01) with the correlation coefficients being ?0.94, ?0.88 and ?0.87 for irrigation and nitrogen experiment, irrigation and cultivars experiment, and tillage, residue and nitrogen experiments, respectively. Further, the regression equation developed between the NDVI - ASD and NDVI - GS: [NDVIGS = 1.070 9 (NDVI - ASD - 0.292] can be successfully used to compute the NDVI of ASD from that computed by GS.Not Availabl

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Not AvailableMaize mostly cultivated in tropical conditions suffers from various biotic and abiotic stresses. Granted, while crop improvement has led to less disease and pest losses due to host plant resistance in maize hybrids, these factors still cause substantial yield losses of maize in India. In the event of incessant rains and unavailability of herbicides, farmers are not able to control weeds through pre-emergence herbicides and manual weeding. Such circumstances, compounded by escalating labor prices, demand effective post-emergence herbicide to manage weeds for sustainable and profitable maize production. To find effective post-emergence herbicides, field experiments were conducted at 20 locations in various agro-ecologies of India for three consecutive years (2015-2017). It was found that weeds caused 32.1 to 59.4% grain yield losses of hybrid maize in the kharif season in India. The losses from the weed in absence of weed management in hybrid maize were maximum in Central Western Zone (55.4 to 60.8%), followed by Northern Hill Zone (43.0 to 49.4%), North Western Plain Zone (44.1 to 49.1%), North Eastern Plain Zone (36.4 to 48.8%); and least in Peninsular zone (26.9 to 40.3%). These losses indicate that the rainfed ecosystem has the maximum yield reduction in kharif maize in central and northern India. The application of Atrazine (1.5kg a.i./ha) as pre-emergence followed by Tembotrione (120ml a.i./ha) at 25 DAS as post-emergence gave the best weed control and higher yield as well as net returns compared to the other pre- and post-emergence herbicide-based management practices at most of the locations. The study suggests that the Tembotrione at 120 ml a.i./ha at 25 DAS could be a better option for weed management in maize in India and similar agro-ecologies.Not Availabl