FS Grospe, AP Sabasaje, GDGracia and Evangeline B. Sibayan
With the increasing cost of fertilizer, one of the major challenges is to increase nutrient-use efficiency in rice production system. Major improvements in fertilizer efficiency are likely to come from improvements in the rice plant, which will enable it to gather nutrients more efficiently or by changing the fertilizer formulation and the methods of application used by farmers. Thus, developing a nutrient management program that takes into account the following aspects such as the indigenous nutrient supply at each site (site-specific), the temporal variability in plant nitrogen status occurring within one growing season (season-specific), and medium-term changes in soil P and K supply based on the cumulative nutrient balance are very important. This study will determine the nutrient use efficiency at different soil fertility levels using the nuclear analytical technique.
Highlights:
Dry Season
• Application of different rate of N fertilizer did not significantly affect the grain yield in soil with low N level. The highest efficiency of applied N was observed at 45 kg N/ha with 50% savings from applied N fertilizer with higher grain yield produced per kg N applied compared with the application of 90kg N/ha (Table 56);
• Grain yield in medium N soil was significantly affected by different N fertilizer applied. Highest yield was obtained at 135kg N/ha and 180kg N/ha. Savings of 33% of N fertilizer applied with higher grain yield produced per kg N applied at 90kg N/ha were obtained compared with 135kg N/ha.
Although the yield at 135kg N was higher than 90kg N/ha, the productivity was lower;
• In high N level soil, yield did not respond to increasing N fertilizer rate. There was no significant difference observed between control and the treated plots. It showed that the inherent soil N was adequate to achieve maximum yield.
• In low P soil, the yield of control plot was not significantly different with those treated plots. This may due to adequate amount of available P in the soil owing to residual P build up after two cropping seasons in the area.
• In medium soil P, highest grain yield was obtained from applied 120kg P/ha. All other treatments (30, 60, 90 Pkg/
ha) produced relatively the same grain yields. application of 30kg P/ha obtained higher ANUE than 60kg P/ha. This can be translated to 50% savings from P fertilizer applied to increased grain yield per kg of P fertilizer applied;
• For high soil P, there were no significant yield differences that were noted among treatments. Maximum yield can be attained even without P fertilizer applied.
• In low K soil level, there was no significant yield differences among treated plots compared to the control. In terms of ANUE, application of 30kg K/ha was significantly higher compared with other treatments. This could be translated to 50% savings of fertilizer K to increased grain yield per kg of grain compared to 60 kg K/ha. More so, 100% savings when compared to 90kg /ha application.
• In medium K soil, grain yields of rice with K application did not significantly differ with the control treatment (0kg K/ha) . This means that comparatively high yield can be achieved even without K fertilizer application. In terms of ANUE based from the control, 30 kg K/ha obtained the highest with 66%
savings when compared from K w/ higher grain yield produced per kg K applied.
• Results of the nuclear analytical analysis for better
understanding on the crop uptake from the fertilizers applied and relate this to grain yield, and nutrient use efficiency will be analyzed in collaboration with PNRI.
Table 56. Grain yield of rice (t/ha), agronomic nitrogen use efficiency (ANUE) in soils with different fertility levels and varying rate of N applied in Region 3, 2014DS.
N rate (kg/ha)
Low N Medium N High N
Yield (t/ha)
ANUE Yield (t/ha)
ANUE Yield (t/ha) ANUE
0 5.0 b - 3.9 d - 6.7 a -
45 6.3 a 27.4 a 5.6 c 39.2 ab 8.0 a 28.9 a
90 6.9 a 19.1 abs 7.6 b 44.0 a 7.4 a 14.6 b
135 7.1 a 15.6 abs 8.6 a 35.0 ab 6.7 a -0.07 b
180 7.0 a 10.8 abs 8.6 a 26.4 b 6.5 a -1.2 b
210 7.2 a 10.4 b 8.4 ab 28.9 b 6.5 a -1.1 b
Wet Season
• Application of high rate of N fertilizer in low N soil during wet season did not significantly increased grain yield. there was no significant difference was noted in the utilization of applied N fertilizer. This indicates that applied N were not fully utilize during wet season probably due to rainfall low solar radiation (Table 57).
• Grain yield in medium soil N level was affected by varying the level of N fertilizer. Application of 45kg N and 90kg N /ha obtained a significantly higher yield than the control and those with 180kg N and 210kg N/ha; Savings of 50% in N fertilizer under low rate N can be achieved when compared with 90kg N/ha application.
• At soils with high medium and low N level, the yield obtained in all treated plots did not significantly differ with the control. Optimum grain yield could also be attained even without application of N fertilizer due to low utilization of applied N in the wet season.
• Optimum yield can achieved even without P fertilizer application.
• There was no significant yield difference observed between the control and the treated plots in soil with low K fertility.
• Results of the nuclear analytical analysis for better
understanding on the crop uptake from the fertilizers applied and relate this to grain yield, and nutrient use efficiency will be analyzed in collaboration with PNRI.
Table 57. Grain yield of rice (t/ha), agronomic nitrogen use efficiency (ANUE) in soils with different fertility levels and varying rate of N applied in Region 3, 2014WS.
N rate (kg/ha)
Low N Medium N High N
Yield
(t/ha) ANUE Yield
(t/ha) ANUE Yield
(t/ha) ANUE
0 3.2 ab - 4.3 b - 5.0 ab
45 3.7 a 12.02 a 5.3 a 21.3 a 5.7 a 15.2 a
90 4.3 a 12.42 a 5.4 a 12.3 a 5.7 a 8.0 a
135 3.4 ab 1.81 a 4.5 ab 1.26 a 5.8 a 6.0 a
180 2.8 b -1.9 a 4.3 b - .10 a 4.7 b 1.5 a
210 2.5 b -3.1 a 3.8 b - 2.3 a 4.7 b -1.2 a
Means within column followed by a small letter are not significantly different at 5% probability using LSD.
ANUE-agronomic nutrient-use efficiency. All N rate had a blanket application of 40kg P and 40kg K/ha in each treatment plot.