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100kg of fertilizer, estimates plant uptake is 80, N balance = +20
Target +30kg balance which provides a safe buffer; farmer unlikely to see yield reduction
There is opportunity to reduce N fertilizer by 20 kg per hectare without impacting the yield
FRAME strategy for addressing excess N use in rice to enhance farm profitability and to reduce GHGs | ||||||||
A.J. McDonald (ajm9@cornell.edu), S.Sherpa (s.sherpa@cgiar.org) | ||||||||
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Kisan yield level (kg/ha)1 | Rice crop N content (kg/ha)2 | Total N rate - upper limit (kg/ha)3 | DAP (kg/ha)4 | Urea (kg/ha) | DAP (kg/acre) | Urea (kg/acre) | DAP (kg/kattha) | Urea (kg/kattha) |
1500 | 36 | 66 | 21 | 135 | 9 | 55 | 0.27 | 1.71 |
1750 | 42 | 72 | 25 | 147 | 10 | 59 | 0.31 | 1.86 |
2000 | 48 | 78 | 28 | 158 | 12 | 64 | 0.36 | 2.00 |
2250 | 54 | 84 | 32 | 170 | 13 | 69 | 0.40 | 2.15 |
2500 | 60 | 90 | 36 | 182 | 14 | 74 | 0.45 | 2.30 |
2750 | 66 | 96 | 39 | 193 | 16 | 78 | 0.49 | 2.45 |
3000 | 72 | 102 | 43 | 205 | 17 | 83 | 0.54 | 2.59 |
3250 | 78 | 108 | 46 | 217 | 19 | 88 | 0.58 | 2.74 |
3500 | 84 | 114 | 50 | 228 | 20 | 92 | 0.63 | 2.89 |
3750 | 90 | 120 | 53 | 240 | 22 | 97 | 0.67 | 3.04 |
4000 | 96 | 126 | 57 | 252 | 23 | 102 | 0.72 | 3.18 |
4250 | 102 | 132 | 60 | 263 | 24 | 107 | 0.76 | 3.33 |
4500 | 108 | 138 | 64 | 275 | 26 | 111 | 0.81 | 3.48 |
4750 | 114 | 144 | 68 | 287 | 27 | 116 | 0.85 | 3.63 |
5000 | 120 | 150 | 71 | 298 | 29 | 121 | 0.90 | 3.77 |
5250 | 126 | 156 | 75 | 310 | 30 | 125 | 0.94 | 3.92 |
5500 | 132 | 162 | 78 | 322 | 32 | 130 | 0.99 | 4.07 |
5750 | 138 | 168 | 82 | 333 | 33 | 135 | 1.03 | 4.22 |
6000 | 144 | 174 | 85 | 345 | 35 | 140 | 1.08 | 4.36 |
6250 | 150 | 180 | 89 | 357 | 36 | 144 | 1.12 | 4.51 |
6500 | 156 | 186 | 92 | 368 | 37 | 149 | 1.17 | 4.66 |
6750 | 162 | 192 | 96 | 380 | 39 | 154 | 1.21 | 4.81 |
7000 | 168 | 198 | 100 | 391 | 40 | 158 | 1.26 | 4.95 |
Notes | |||||||||||
1 Maximum farmer yield level achieved in the last three years | |||||||||||
2 Estimated N content in rice plant to support maximum achieved yield (above-ground DM estimated by assuming a HI of 50% and 20% MC); assumes an N concentration of 1.5% concentration in dry matter per IRRI knowledge bank | |||||||||||
3 Upper limit for N application with an N-balance target of + 30 kg/ha with N inputs based solely on inorganic fertilizer and outputs estimated for grain and straw w/ complete removal | |||||||||||
4 DAP rate determined by crop P requirement at full replacement levels for crop removal; assumes a P2O5 concentration of 0.64% in rice above-ground dry matter per IRRI knowledge bank |
Key messages: | |||||||||||||||||||||||||
If farmers are applying more N than the upper limit for their maximum achieved yield level, reductions in N rate are possible without reducing yields. These farmer should be encouraged to reduce their N usage to the corresponding upper limit rate. | |||||||||||||||||||||||||
If farmers are applying less N than the upper limit for their maximum achieved yield level, they should maintain their current rate unless they are interested in increasing yields. For famers who wish to increase yields, they can be encouraged to experiment with a moderately higher N rate (i.e. add an additional 25 kg/ha) to determine if there is a yield gain that can be achieved with additional N. |
2: Usage and utility of leaf color chart
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Start LCC readings from 14 DAT (Days after Transplantation) or 21 DAS (Days after sowing)
The last reading is taken when the crop just starts to flower.
Randomly select at least 10 disease-free rice plants or hills in a field with uniform plant population from different areas of the plot.
Select the topmost fully expanded leaf from each hill or plant
Place the middle part of the leaf on a chart and compare the leaf color with LCC shades
Do not detach or destroy the leaf
Measure the leaf color under the shade of your body, because direct sunlight affects leaf color readings
If possible, the same person should take LCC readings at the same time of the day every time
If more than five leaves read below a set critical value, apply
23 kg N ha-1 (one 50-kg bag of urea/ha) for wet season or
The suggested critical values are:
4 for transplanted rice (TPR)
3 for high-density wet-seeded rice (WSR)
Repeat the process at 7 to 10 day intervals or at critical growth stages (early tillering, active tillering, panicle initiation, and first flowering) and apply N as needed.
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