EFFECT OF NITROGEN NUTRITION AND GROWTH REGULATORS ON CROP GROWTH ATTRIBUTES IN BLACK GRAM (Vigna mungo L.) Hepper. K.Krishna Surendar*, Mallika Vanagamudi and H.Vijayaraghavan Department of Crop Physiology, Tamil Nadu Agricultural University,Coimbatore-3 ABSTRACT In the experiment conducted during July to October, 2007 to examine the effect of nitrogen nutrition and growth regulators on dry matter accumulation, CGR, NAR, SLW and LAI in black gram variety CO-5. Basal application of N P K and urea 2 % was common for all the treatments. In T3 an addition dose of nitrogen @ 25 kg ha-1 was given. The foliar spray was given at 25 DAS and 10 days after the first spray. The basal application of nitrogen 25kg ha-1 with foliar spray of urea 2% and 0.1 ppm brassinolide significantly increased the dry matter accumulation. Other growth attributes via, LAI, CGR, NAR, and SLW increased with the basal application of nitrogen 25kg ha-1 with foliar spray of urea 2% and 0.1 ppm brassinolide as compared to other treatments. Key Words: Nitrogen nutrition, plant growth regulators LAI, CGR, NAR, SLW, dry matter accumulation.
INTRODUCTION Black gram is a widely grown grain legume and belongs to the family fabaceae and assumes considerable importance from the point of food and nutritional security. It is a short duration crop suitable for multiple cropping systems and intercropping. . The average productivity of pulses in Tamil Nadu is about (432kg ha-1) which is very low when compared to Indian average of 610 kg ha-1. The important factors which reduce the Black gram yield are, indeterminate in its flowering and fruiting habits and there is a competition for available assimilates between vegetative and reproductive sinks. There is limitation of source (leaves) particularly at flowering and fruiting stage. Hence, there is a need to improve Leaf Area Index, Crop Growth Rate, Net Assimilation Rate and Specific Leaf Weight. Being a C3 plant, CGR and RGR are relatively less than cereals. Apart from this genetic make up, the major physiological constraints limiting its production is flower drop and fruit drop (Ojeaga and Ojehomon, 1972). Therefore, present study was conducted to examine the effect of nitrogen nutrition and plant growth regulators on the regulation of growth attributes of black gram. The research experiment was carried out at millet Breeding Station, Tamil Nadu Agricultural University, Coimbatore during July to October, 2007. The experimental site is located at 11o E longitude and 77o N latitude in an altitude of 426.8m above MSL. The soil was sandy loam in texture having 27.4 %, PH 8.7, EC 0.22 dSm-1, 10.3 % fine sand, 10.7 % silt, 22.6% clay, available N,P,K are 207, 21, 554 kg ha-1. The experiment was laid out in randomized block design with three replications. Nine treatments were taken, T1 (control), T2 (N 25 kg ha-1 + Urea 2% + NAA 40ppm), T3 (N 50 kg ha-1 + CCC 200 ppm), T4 (N 25 kg ha-1 + Urea 2% + CCC 200ppm), T5 (N 25 kg ha-1 + Urea 2% + Humic acid 0.1%), T6 (N 25 kg ha ha-1 + Urea 2% + Salicylic acid 100 ppm) T7 (N 25 kg ha ha-1 + Urea 2% + Brassinosteriod 0.1 ppm), T8 (N 25 kg ha ha-1 + Urea 2% + ZnSO4 0.5% + FeSO4 0.5% + Borax 0.2%), T9 (N 25 kg ha-1 + water spray), were imposed at 25 DAS and 10 days after the first spray. Dry matter accumulation of plant parts (root, stem, leaves and pods) was recorded at vegetative, flowering, pod filling and harvest stages from five plants in a row. The mean monthly minimum and maximum temperature during the crop season from 23.1o C to 29.6o C respectively. Leaf area was recorded by using leaf area meter (Model LICOR 3100). The samples were oven dried at 70oC for about 72 hours and dry weight was recorded. Leaf Area Index, Crop Growth Rate, Net Assimilation Rate, Specific Leaf Weight were calculated by employing the formula of Williams (1946), Pearce et al. (1968), Watson (1956) and Gregory et al. (1917).
RESULT AND DISCUSSION Basal application of nitrogen 25 kg ha-1 with foliar spray of urea 2% and 0.1 ppm brassinolide enhanced dry matter accumulation by 25 per cent over control at the final stage of the crop (table 1). Besides this treatment, CCC 200ppm + urea 2 % with normal N 25 kg ha-1 also found better in improving the total dry matter production by 18 per cent over control. The physiological parameters viz. Leaf Area Index, Crop Growth Rate, Net Assimilation Rate, Specific Leaf Weight were significantly influenced by the application of nitrogen 25kg ha-1 with foliar spray of urea 2% and 0.1 ppm brassinolide at flowering and pod filling stage of the crop (35 and 40 %, 30 and 33%, 20 and 28 %, 12 and 11.6 % ). Basal application of nitrogen 25kg ha-1 with foliar spray of urea 2% and 0.1 ppm brassinolide at flowering and pod filling stages were found significantly better over control. Specific leaf weight is a measure of leaf thickness has been reported to have a strong positive correlation with leaf photosynthesis of several crops as reported by Bowes et al. (1972). Thicker leaves would have mere number of mesophyll cells with high density of chlorophyll and therefore, have a greater photosynthetic capacity than thinner leaves (Craufurd et al. 1999). Watson (1958) suggested that the cause for the decrease in net assimilation rate with increased leaf area in crop plants was due to mutual shading of the leaves which would decrease the leaf photosynthesis. Crop production is determined by crop growth rate as a function of light interception by the leaf area of a crop (Whigham, 1983). Leaf area index is one of the principle factors influencing canopy net photosynthesis of the crop plants (Hansen, 1972). Better foliage retention with delayed senescence was attributed to maintenance of higher leaf area index if this crop subjected to the treatment with high nitrogen dose.
Stages
Treatments TOTAL DRY MATTER PRODUCTION (g plant-1)LEAF AREA INDEX (LAI)SPECIFIC LEAF WEIGHT (SLW) (mg cm2) VSFSPFSHSVSFSPFSHSVSFSPFSHS T11.833.838.8913.680.280.611.351.184.7612.0612.5510.90 T21.944.210.0515.520.320.711.701.385.4912.0912.6112.40 T31.964.4210.3115.650.320.791.871.625.9913.4613.6512.78 T42.064.7110.4316.160.320.761.801.595.7012.7013.0512.71 T51.883.979.5415.440.310.661.591.495.6712.0412.6912.53 T61.873.969.7914.680.310.691.641.415.6512.0312.6811.31 T72.124.8410.5817.140.340.821.891.656.0113.5213.6813.08 T81.924.149.414.430.320.721.761.505.6812.5412.7312.60 T91.854.169.2914.580.300.651.501.335.3512.0612.5611.04 Mean1.944.259.8115.280.310.711.671.465.6112.4712.8812.09 SEd0.080.170.410.640.010.020.060.060.230.520.540.50 CD (P=0.05)0.170.370.871.360.030.060.140.120.491.121.161.07 VS-VEGETATIVE STAGE, FS-FLOWERING STAGE, PFS-POD FILLING STAGE, HS-HARVEST STAGE. Table 1. Effect of Nitrogen Nutrition And Growth Regulators On TDMP, LAI and SLW VEGETATIVE STAGE, FS-FLOWERING STAGE, PFS-POD FILLING STAGE, HS-HARVEST STAGE. Table 2. Effect of Nitrogen Nutrition And Growth Regulators On CGR And NAR
Stages
Treatments CROP GROWTH RATE (CGR) (g m-2 day-1)NET ASSIMILATION RATE (NAR) (mg cm-2 day-1) VG-FSFS-PFSPFS-HSVG-FSFS-PFSPFS-HS T10.541.221.020.550.500.48 T20.561.281.070.600.580.57 T30.711.621.200.650.640.61 T40.601.531.210.640.600.59 T50.611.441.030.590.570.55 T60.551.511.090.570.540.52 T70.781.841.360.660.650.63 T80.591.421.010.620.590.56 T90.601.581.040.560.520.50 Mean0.611.491.110.610.580.56 SEd0.020.060.040.020.020.02 CD (P=0.05)0.050.130.080.050.050.05 Reference:
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