Effect of nutrient omission on wheat growth, yield, nutrient uptake and photo-thermal indices under late sown conditions
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Date
2023
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RPCAU, Pusa
Abstract
A field experiment was conducted in wheat (Triticum aestivum L.) in rabi season at Experimental farm of the Dr. Rajendra Prasad Central Agricultural University in Pusa, Bihar during 2022-23. Among the agronomic factors, sowing date and nutrients also play important role in field crops such as wheat which influence the plants growth stages, especially vegetative and reproductive stage. Any delay leads to substantial decrease in wheat productivity. Under Bihar conditions, optimum wheat sowing time is second forthnight of November but due to late harvesting of kharif crop (rice), there is delay in sowing of wheat. In this situation, there is only option that we have to go for late sowing of wheat. However, late sown wheat faces terminal heat stress leads to decline in wheat productivity. Late sowing also limits the fertilizer response which is also important factor responsible for obtaining higher yield. In the nutrient limited conditions, productivity of wheat can be affected. So, there is a need to determine the optimum sowing time at which wheat can be grow without any reduction in yield under late-sown conditions.
Keeping this view, field experiment entitled “Effect of nutrient omission on wheat growth, yield, nutrient uptake, and photo-thermal indices under late sown conditions’’ was implemented with the objectives to evaluate the effect of sowing date on growth, yield and photo-thermal indices in wheat and to analyze the soil and plant nutrients at different growth stages of wheat and economics of different treatments. The experiment had 10 treatments, laid out in split plot design with three replications. Main plot treatments comprised two sowing date (December 1 and December 21) and five (05) sub-plot treatments (100% NPK, 100 % PK (N omission), 100% KN (P omission), 100% NP (K omission) and absolute control. Growth attributes was significantly affected by the sowing date factor. Crop sown at December 1 were produced taller plants as compared to December 21 sown crops at all growth phases. Plant height, no. of tiller m-2 and dry matter accumulation (DMA), crop growth rate (CGR) increased with the advancement of crop growth and developmental stages. However, there was no differences in these growth parameters was observed at 30 DAS while significant effect was exerted by the sowing date factor at 60, 90 and at harvest. At maturity, maximum plant height (83.5 cm), no. of tiller m-2 (246), DMA (880 g m-2) and CGR 13.3 g m-2 day-1) was found when sown at Dec.1 compared to Dec.21 sown wheat. At harvest, it was increased by 18.6, 18.8 41.5 and 41.3 %. Nutrients factor significantly impacted these growth attributes. Plots receiving 100 % NPK produced tallest plant in comparison to plots not receiving any source of fertilizer and being statistically similar with 100 % PK, 100 %KN.
At December 21 sowing date, there is significant reduction in leaf area index (1.41 and 1.94) at 60 and 90 DAS respectively was observed as compared to December 1 sown crop. Markedly decline in wheat yield parameters and yield due to very late sown crop (Dec.21) observed over Dec.1 sown plants which is accounting 28.3, 30, 9.6 ,4.8 ,44.3 and 37.5 % in number of effective tillers, spike length, no. of grain per ear, grain and straw yield respectively.
Nutrient’s factor influenced grain yield significantly and maximum values observed with 100 % NPK compared to absolute control and being statistically at par with 100% NK (P omission) and 100 % NP (K omission). While substantial decline was found in 100 % PK (N omitted plots) and it was to the tune of 50.9 % reduction in grain yield due to N omissions during the experiment as nitrogen is very important nutrient for plant growth and development throughout the period. N continued to be the most limiting nutrient followed by P and K. Growing degree days (GDD), helio-thermal unit (HTU), photo-thermal unit (PTU) significantly affected by the sowing date factor from sowing to tillering and tillering to flowering stage then after there were non-significant effect on GDD, HTU and PTU at flowering to milking and milking to maturity stage while pheno-thermal index (PTI) remains unaffected by both factors. Significantly higher GDD (615 and 11800C day), HTU (1878 and 52800C day hour) and PTU (6561 and 130350C day hour) was found when sown at Dec.1 at sowing to tillering and tillering to flowering respectively.
Nitrogen, phosphorus and potassium availability did not significantly influence by sowing date factor. However, significant effect was exerted by nutrients factors on NPK availability. Nitrogen, phosphorus and potassium content in soil was found significantly higher with 100 % NPK compared to compared plot and being statistically at par with 100% KN, 100% NP applied plots. In comparison to the control plot, the 100% NPK treatment resulted in 21.9, 23.9, 25.9, and 25.7 % more available N in soil at 30, 60, and 90 DAS, as well as at harvest, whereas the 100% NPK treatment resulted in 30.3, 38.0, 44.3, and 49.3 % more available P in soil at 30, 60, and 90 DAS, as well as at harvest. Plots treated with 100% NPK had 35.7, 44.6, 47.8, and 51.7 % more accessible K2O than the absolute control plots.
The N, P, and K uptake in plant was higher in 1 December sowing, and the uptake was increasing towards maturity. In comparison to the absolute control plots, 100% NPK plots showed 42.5, 64.9, and 67.5 % greater N uptake in plant at 30, 60, and 90 DAS, respectively. As well as P uptake, was also higher with 100% NPK, which was 46, 69.7, and 66.5% over the control plot at 30, 60, and 90 DAS, respectively. The use of 100% NPK resulted in much higher K uptake in plant than the other treatment. However, at 30, 60, and 90 DAS, it resulted in 37.8, 63.2, and 66.3% higher K uptake in plant than the control plot, respectively. The N, P, and K uptake in grain and straw was higher in 1 December sowing than in 21 December sown crops, accounting for 25.6, 29.8, and 20.8% in grain and 21.5, 2.8, and 23.7 % in straw, respectively. While 100% NPK applied plot had higher NPK uptake in grain and straw compare to control plot, it accounting 69.2, 69.2, 60.9 % in grain and 72.6, 63.9, 60.7% in straw respectively. Highest net profit of ₹ 53492 ha-1 and B: C ratio 1.39 was earned when sown at Dec.1 compared to Dec.21 in wheat during the experimental period. Thus, from the results, we can conclude that upto Dec.1 sowing of wheat is appropriate. Beyond this date, there is significant reduction in wheat productivity and nutrient limited conditions will also led to poor growth and development of the crop resulting into substantial decline in yield.