Effects of Naphthalene acetic acid and sowing time on fertilizer use efficiency and yield of wheat (Triticum aestivum L.)

Abstract

The present research work was mostly carried out in the Plant Physiology, Biochemistry and Plant Nutrition Laboratory of the Department of Botany and partly in the Department of Soil Water and Environment, University of Dhaka and also in Bangladesh Council of Scientific and Industrial Research (BCSIR )to study the effect of Naphthalene acetic acid (NAA ) and sowing time on wheat (Triticum aestivum L.). The investigation consists of recording and estimating different physiological and biochemical parameters through which yield was affected and finally to evaluate the fertilizer use efficiency (FUE )by wheat plants. In the course of present investigation four field experiments were carried at the Botanical Garden of the Department of Botany, University of Dhaka for three consecutive years during the period from 2014 to 2017. First experiment was conducted with six high yielding varieties of wheat (var. BARI Gom-23, BARI Gom-24, BARI Gom-25, BARI Gom-26, BARI Gom-27 and BARI Gom-28)in four sowing time (November 15, November 22, November 29 and December 04)during 2014-2015 season for selection of the best performed variety and optimum sowing time. Second experiment was carried out in selected optimum time (November 15)of 2015-2016 using different concentrations of NAA (0, 10, 20, 30, 40, 50 and 60 ppm )as foliar spray in combination with various Nitrogen (N )levels (0%, 25%, 50%, 75% and 100% of the recommended dose )on the selected variety of wheat (BARI Gom-25). Third experiment was also carried out during 2015-2016 in selected optimum time with lower concentrations of NAA (0, 10, 20 and 30 ppm ) as seed soaking treatment in combination with the recommended dose of N-fertilizer on the selected variety. During 2016-2017 fourth experiment was carried out using best foliar and seed soaking treatments in combination with varying N-levels at two sowing time (timely and 7 days late sown). Results obtained during 2014-2015 season revealed that the maximum plant height was recorded from BARI Gom-24 at most of the ages and seed sown on November 29 produced tallest plant all over the ages whereas, December 04 sown wheat produced the shortest plant in BARI Gom-28 from 75 days after sowing (DAS ) up to harvest. Results also revealed that seeds sown on November 15 produced the highest number of tillers, leaves and total dry matter (TDM )per plant in BARI Gom-25 with few exceptions. Yield contributing characters viz. number of grains per plant, dry weight of spike, 1000-grain weight, yield per plant and hectare and harvest index were recorded maximum from BARI Gom-25. November 15 sown wheat resulted maximum values in all yield contributing parameters with significant responses except the number of non-effective tillers per plant. Combined effects of variety and sowing time showed that November 15 sown BARI Gom-25 also resulted maximum number of effective tillers per plant (8.13), number of grains per plant (236.79), dry weight of spike (24.17 g ), 1000-grain weight (50.64 g ), yield per plant (11.99 g )and per hectare (6.00 t )and harvest index (30.92% )where, it was significantly higher than rest of the treatments in case of dry weight of spike, 1000-grain weight, yield per plant and per hectare. Results obtained from the second experiment during 2015-2016 revealed that foliar spray of NAA and N-fertilizer had mostly stimulatory responses on plant height where, full dose of N-fertilizer without foliar NAA produced maximum plant height throughout the ages. Number of tillers per plant of BARI Gom-25 was nonsignificantly

affected by NAA treatments whereas, higher doses of N-fertilizer produced higher number of tillers per plant all over the ages. Spraying of 20 ppm NAA in combination with full doses of N-fertilizer although produced higher number of tillers per plant than all other combination treatments but statistically not different from some other treatments including 20 ppm in combination with 25% N-fertilizer. Application of NAA treatments had mostly non-significant responses on the number of leaves of BARI Gom-25 whereas, different levels of N-fertilizers produced significantly higher number of leaves per plant at most of the ages. Number of leaves per plant noted at harvest from full dose of N-fertilizer without any NAA was significantly higher than all other combinations except 75% N-fertilizer without NAA. The TDM per plant were positively influenced following application of NAA and N-fertilizer and also by their combinations at most of the ages. Application of 20 ppm NAA in combination with full doses of fertilizer although resulted highest TDM per plant but statistically not different from 20 ppm NAA in combination with 25% fertilizer dose at most cases. Findings also indicated that 20 ppm NAA in combination with 25% fertilizer resulted higher TDM than full dose of fertilizer alone. Spraying of 20 ppm NAA had resulted maximum number of effective tillers per plant, length of spike, number of grains per spike and per plant, dry weight of spikes, yield per plant and per hectare but with statistically identical value to rest of the treatments. Different doses of N-fertilizer although produced higher number of effective tillers per plant, number of grains per plant, dry weight of spikes, yield per plant and per hectare but were statistically at par to each other. Results obtained from combined application of NAA and N-fertilizer showed that combination of 20 ppm NAA and full dose of N-fertilizer although resulted maximum number of effective tillers per plant but statistically identical to many other combinations with lower doses of fertilizer including 20 ppm NAA at 25% N-level. Number of non-effective tillers per plant was influenced non-significantly due to all combined treatments. Application of 20 ppm NAA at 25% N-level had resulted maximum length of spike (9.13 cm )and number of grains per spike (35.13). Results also showed that number of grains per plant (115.92), dry weight of spike (7.07 g ), yield per plant (5.26 g )and per hectare (2.63 t )obtained from 20 ppm NAA at 25% N-level were statistically not different from other combined treatments including 20 ppm NAA in combination with full dose of N-fertilizer. Yield per plant increased by 107.28 and 101.53% due to 20 ppm NAA in combination with full dose of N-fertilizer and in combination with 25% N-fertilizer respectively. The maximum harvest index (43.18% )was noted from 40 ppm NAA in combination with 50% N-level which was statistically similar to control. Findings showed that spraying of NAA treatments resulted significantly higher chlorophyll a (chl. a ) and carotenoids contents of leaves at tillering stage with few exceptions. Application of 50, 75 and 100% of the recommended N-fertilizer produced significantly higher chl. a content at all stages viz. tillering, flowering and grain filling and carotenoids content at tillering stage in majority of cases. Combination of NAA and fertilizer had significant influences upon pigment contents of leaves at all stages except chl. b content at grain filling stage. Outcome of experiment 3 conducted during 2015-2016 revealed that seed soaking with 10 ppm NAA in combination with recommended N-fertilizer produced better stimulations in plant height, number of tillers, number of leaves and TDM per plant with significant variations in majority of cases. Number of effective tillers per plant (5.75), number of grains per plant (185.48), dry weight of spikes (9.23 g ), yield per plant (8.23 g)and per hectare (4.12 t )were recorded maximum from seed soaking with 10 ppm NAA in combination recommended N-fertilizer treatment and were significantly higher than control in case of number of effective tillers per plant, number of grains per plant and yield per plant and per hectare. Results showed that yield per plant increased by 16.08 and 13.68% following seed soaking with 10 ppm and 20 ppm NAA in combination recommended dose of N-fertilizer respectively. However yield per plant due to seed soaking with 30 ppm NAA in combination with recommended N-level reduced by 8.85%. Significantly higher pigment content of leaves both at tillering and grain filling stages were also obtained from 10 ppm NAA with recommended dose of N fertilizer treatment. In the fourth experiment, during 2016-2017 season, seed soaking with 10 ppm NAA in combination with 75% N-fertilizer resulted taller plant, maximum number of tillers and leaves per plant in most of the growth ages at both timely and late sown condition where, it were significantly higher than the most of treatments. Results revealed that late sown wheat produced comparatively taller plant than timely sown. However, timely sown wheat produced higher number of tillers per plant than late sown condition but statistically at par with full dose of N-fertilizer alone and in combination with 10 ppm seed soaking treatment. Seed soaking with 10 ppm NAA in combination with 75% N-fertilizer also produced maximum dry matter per plant throughout the growth ages at both sowing time where it was significantly higher than all other treatments including full dose of N-fertilizer. Seed soaking with 10 ppm NAA in combination with 75% N-fertilizer resulted maximum values on various yield parameters and yield of BARI Gom-25 at both timely and late sown condition with few exceptions. In case of timely sown BARI Gom-25, number of grains per plant (198.08), dry weight of spikes (16.54 g ), 1000-grain weight (45.80 g ), yield per plant (7.75 g )and per hectare (3.88 t )recorded from seed soaking with 10 ppm NAA in combination with 75% N-fertilizer (best performed treatment )were significantly higher than the majority of treatments including full dose of N-fertilizer. Yield per plant of timely and late sown BARI Gom-25 obtained from the best performed treatment were 24.80 and 19.24% higher than that of recommended dose of N-fertilizer. Results also indicated that yield per plant reduced by 5.56% at 7 days late sowing. The best performed treatment had also significant beneficial effect on different biochemical components viz. leaf pigments, nutrient uptake, nitrogen use efficiency, nutritional value, enzyme activities, amino acid and mineral contents. Findings revealed that the best performed treatment with few exceptions produced significantly higher pigment contents than full dose of N-fertilizer at all stages in both timely and late sown condition. Nitrogen (N ), phosphorus (P ) and potassium (K ) contents of shoot, root and grain were affected significantly following all treatments at all stages viz. flowering, grain filling and harvest in both sowing time. Significantly maximum NPK uptake by shoot, root and grain was also obtained from the best performed treatment at flowering and harvest stages in majority of cases of both sowing time. At grain filling stage, the best performed treatment also resulted significantly higher NPK uptake than full dose of N-fertilizer in both cases except uptake by root of timely sown wheat. Nitrogen use efficiency (NUE ) due to NAA at varying N levels were significantly higher than full dose of fertilizer in most cases at both sowing time. During 2016-2017 season, considering yield performances, three treatments (control, 100% of recommended dose of N-fertilizer and best performed treatment )of timely sown BARI Gom-25 were selected for comparative analysis on some nutritional parameters, amino acid contents, enzyme activities and mineral contents of grain. Results showed that the best performed treatment produced significantly higher amount of protein (17.81% ), starch (52.69% ), total ash (1.96% ), total sugar (5.65% )and reducing sugar (0.92% )contents than control and full dose of N-fertilizer treatment. Increase in starch, protein, total ash, total sugar and reducing sugar contents following the best performed treatment were 1.64, 2.65, 7.69, 1.25 and 10.84% higher over full dose of N-fertilizer respectively. Carbohydrate content following the best performed treatment was recorded higher than full dose of N-fertilizer. Although the maximum fat content (1.69% )was obtained from full dose of N-fertilizer but statistically at par to the best performed treatment. However, moisture content of grain decreased significantly due to both full dose and best performed treatments. Amino acids viz. aspartic acid, serine, glutamic acid, glycine, alanine, valine, isoleucine, leucine, tyrosine, histidine, lysine and arginine were recorded maximum following the best performed treatment. In case of threonine (0.35% )and methionine (0.26% )in addition to the best performed treatment the maximum was also recorded from full dose of N-fertilizer treatment. Findings indicated that the amount of aspartic acid (0.74% ), glutamic acid (3.71% ), leucine (0.88% ), lysine (1.01% )and arginine (1.89% )recorded were significantly higher than both control and full dose of N-fertilizer treatments, whereas, those of serine, glycine, valine, isoleucine, tyrosine and histidine are statistically not different from full dose of N-fertilizer treatment. Amino acids viz. aspartic acid, serine, glutamic acid, glycine, alanine, valine, isoleucine, leucine, tyrosine, histidine, lysine and arginine increased by 2.78, 1.82, 2.77, 3.92, 2.08, 3.70, 2.33, 3.53, 3.45, 2.94, 3.06 and 2.16% over F4 treatment respectively. Enzyme activities of grain were positively influenced by different treatments where, significantly higher α-amylase content was recorded from the best performed treatment. Increases in α-amylase and protease activities following the best performed treatment were 23.08 and 27.27% over control and 6.67 and 9.80% over full dose of N-fertilizer treatment respectively. Mineral viz. N, K, Fe and Ca contents were also noted maximum from the best performed treatment and in case of Ca it was significantly higher than control and full dose of N-fertilizer. However, the amount of P and Zn was obtained maximum from full dose of N-fertilizer whereas, in case of P content it was not significantly different from that of best performed treatment. Findings indicated that NAA had beneficial effect on growth and yield of BARI Gom-25 when applied as seed soaking treatment rather than foliar spray. Seed soaking with 10 ppm NAA and applying 25% less urea, the yield of timely sown wheat could be increased up to 24.80%. By reducing the demand of nitrogen fertilizer up to 25%, this best performed treatment not only increase the yield of wheat but remarkably improved the quality of grain. From the cost benefit analysis, it was also revealed that seed soaking with 10 ppm NAA at 75% N-level treatment could add 17,500 Taka more benefit in per hectare area. Thus, use of 10 ppm NAA as seed soaking treatment is economically advantageous and could be used in farmer level for higher production of wheat.