REAL TIME NITROGEN MANAGEMENT IN RABI MAIZE (Zea mays L.) USING LEAF COLOUR CHART UNDER VARIED PLANT DENSITY
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Date
2019
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Acharya N G Ranga Agricultural University, Guntur
Abstract
The present investigation entitled “Real time nitrogen management in rabi maize (Zea mays L.) using leaf colour chart under varied plant density” was carried out for two consecutive rabi seasons of 2017-18 and 2018-19 at wetland farm of S.V. Agricultural College, Tirupati campus of Acharya N.G. Ranga Agricultural University of Andhra Pradesh. The experiment was laid out in split-split plot design with three replications. The treatments consisted of three planting densities viz., 66,666 plants ha-1 (P1), 83,333 plants ha-1 (P2) and 1,11,111 plants ha-1 (P3) assigned to the main plots, three nitrogen levels i.e. 30 kg N ha-1 (N1), 35 kg N ha-1 (N2) and 40 kg N ha-1 (N3) allotted to sub plots and three LCC threshold values viz., LCC 4 (L1), LCC 4.5 (L2) and LCC 5 (L3) as sub-sub plots. The test variety was DHM-117.
Planting density, nitrogen doses and LCC threshold values significantly influenced the growth parameters, yield attributes, yield, nutrient uptake, economics and post harvest soil fertility status.
Significantly higher values of growth parameters (plant height, leaf area index, total dry matter production, crop growth rate) were obtained with higher planting density of 1,11,111 plants ha-1 (P3), over 83,333 plants ha-1 (P2) and 66,666 plants ha-1 (P1), during both the years of study. However, leaf area plant-1 and SPAD chlorophyll values, were found significantly higher at lower planting density of 66,666 plants ha-1 (P1). With regards to various nitrogen levels, application of 40 kg N ha-1 (N3) recorded significantly taller plants with higher dry matter accrual, which was at par with 35 kg N ha-1 (N2) and significantly superior over 30 kg N ha-1 (N1), during both the years. Higher LCC threshold value i.e. LCC 5 (L3) recorded maximum aforesaid growth parameters, followed by LCC 4.5 (L3) and LCC 4 (L1). With regard to interaction effect, planting density and nitrogen levels was found to be
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significant at 90 DAS and at harvest. The combination of higher planting density (1,11,111 plants ha-1) along with higher nitrogen level (40 kg N ha-1) produced maximum dry matter and was significantly higher over rest of the treatment combinations, however, lower dry matter production was obtained with P1N1 (66,666 plants ha-1 and 30 kg N ha-1) which was statistically comparable with P1N2 (66,666 plants ha-1 and 35 kg N ha-1).
Number of days to 50 % tasseling and silking was significantly lower in maize at lower planting density of 66,666 plants ha-1 (P1) followed by 83,333 plants ha-1 (P2) and 1,11,111 plants ha-1 (P3). A progressive reduction in number of days to 50 % tassel and silk emergence was noticed with lower application of 30 kg N ha-1 (N1), which was however, comparable with 35 kg N ha-1 (N2) and flowering was delayed with 40 kg N ha-1 (N3). Application of nitrogen using lower LCC threshold values of LCC 4 (L1) recorded minimum days required for 50 % flowering.
Maize sown with lower plant density (66,666 plants ha-1) recorded higher yield attributes i.e. number of cobs plant-1, cob length, cob girth, number of kernel rows cob-1, number of kernels row-1, number of kernels cob-1 and seed index over other two higher plant densities during both the years. Significantly higher yield viz., cob, kernel and straw yields were noticed in maize when sown at higher planting density of 1,11,111 plants ha-1 (P3) followed by planting density of 83,333 plants ha-1 (P2) and 66,666 plants ha-1 (P1). The maximum values with respect to yield attributes and yield were noticed with the application of 40 kg N ha-1 (N3) compared to rest of the nitrogen levels. Application of nitrogen using higher LCC threshold values of LCC 5 (L3) recorded maximum yield attributing characters and yield than LCC 4.5 (L3) and LCC 4 (L1). With regard to interaction, planting density, nitrogen levels and LCC threshold values were found to be non-significant with yield parameters like number of cobs plant-1 and cob length, during both the years of study. However, cob girth exerted significant interaction on planting densities with nitrogen levels (P x N) and LCC threshold values (P x L) during first year of study.
Interaction of planting density and LCC threshold values was found to be significant with regard to number of kernel rows cob-1 and number of kernels row-1, however it was found to be maximum with planting density of 66,666 plants ha-1 using LCC threshold 5 (P1L3). Number of kernels cob-1 was influenced by the interaction of planting density, nitrogen levels and LCC threshold values. Maximum number of kernels row-1 and number of kernels cob-1 was recorded with the combination of lower planting density (66,666 plants ha-1) along with higher nitrogen levels (40 kg N ha-1) using LCC threshold 5 (P1N3L3), which was however statistically comparable with planting density of 83,333 plants ha-1 coupled with 40 kg N ha-1 using LCC threshold 5 (P2N3L3). During both the years of study, interaction between planting density and nitrogen levels was significant with regard to cob, kernel
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and straw yield, however, higher planting density of 1,11,111 plants ha-1 along with application of 40 kg N ha-1 recorded significantly maximum yield.
Uptake of nitrogen, phosphorus and potassium at various growth stages and nitrogen use efficiency was found significantly higher at higher planting density of 1,11,111 plants ha-1 (P3), which was superior to other two planting densities. Nutrient uptake at various growth stages of crop and nitrogen use efficiency increased significantly with increase in nitrogen levels from 30 to 40 kg ha-1 at different splits based on higher LCC threshold value of LCC 5 (L3). Among the interactions, planting density and nitrogen level was significant at 60 DAS, during both the years of study. Whereas, combination of higher planting density (1,11,111 plants ha-1) with higher nitrogen level (40 kg N ha-1) registered significantly higher nitrogen uptake and other interactions were non-significant. Phosphorus uptake and interaction of planting density and nitrogen level was significant during both the years however, maximum phosphorus uptake was noticed with higher planting density of 1,11,111 plants ha-1 coupled with higher level of 40 kg N ha-1 (P3N3) at harvest. At harvest, during first year of study, interaction of planting density, nitrogen level and LCC threshold values was significant with respect to phosphorus uptake and it was found maximum with combination of P3N3L3. Among the various growth stages of maize interaction of all the three tested factors was found to be non-significant except at harvest between planting density and nitrogen level during both the years of study, however uptake of potassium was estimated higher at the combination of higher planting density with higher nitrogen levels (P3N3).
The post harvest soil fertility status (available nitrogen, phosphorus and potassium) decreased significantly with higher planting density, during both the years of field investigation. There was significant improvement in soil fertility status with higher level of nitrogen (40 kg ha-1) application at different intervals using higher LCC threshold value 5 (L3). With regard to interaction, planting density and nitrogen levels was found significant with respect to available soil nitrogen, phosphorus and potassium, during both the years. The combination of lower planting density and higher level of nitrogen application (P1N3) resulted in maximum status of soil fertility after harvest of the crop during both the years. However, interaction of all three tested factors was found significant with respect to potassium uptake, during the second year of study, maximum available potassium status of soil was found in the treatment combination of 66,666 plants ha-1 coupled with application of 40 kg N ha-1 using higher LCC threshold 5 (P1N3L3).
The higher gross monetary returns, net monetary returns and returns per rupee invested were realized at higher planting density of 1,11,111 plants ha-1 (P3). Among the nitrogen level tested, application of 40 kg N ha-1 (N3) using higher LCC threshold 5 (L3) resulted in higher gross monetary returns, net monetary returns and returns per rupee invested. With regard to interaction, during the first year of study, planting density and nitrogen level was found
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significant with respect to gross and net monetary returns, however combination of higher planting density and higher level of nitrogen application (P3N3) registered significantly maximum gross and net monetary returns. During both years, combination of lower planting density at lower level of nitrogen (P1N1) recorded minimum economic returns.
Based on the outcome of the investigation, it can be concluded that blanket recommendation or fixed time split application of nitrogen is not adequate for obtaining higher productivity and higher nitrogen use efficiency in maize. Hence, there is ample scope for increasing production and productivity of maize hybrid, with higher planting density of 1,11,111 plants ha-1 supplied with 40 kg N ha-1 as need based top dressing using LCC threshold 5 (LCC 5) along with basal application of 60 kg N ha-1.
Description
D5834
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