Nutrient status of potatoes grown on compost amended soils as determined by sap nitrate levels.

Transcription

1 Nutrient status of potatoes grown on compost amended soils as determined by sap nitrate levels. Katherine Buckley, Ramona Mohr, Randy Westwood Brandon Research Centre, AAFC Van Coulter, Kristen Phillips, MAFRI 21st Annual National Compost Conference September 19-21, 2011 Charlottetown, PEI

2 Acknowledgement Agricultural Sustainability Initiative

3 Potato Fertility Management Adequate N during growth stages I and II will result in enhanced tuber initiation and set. Critical time for N supply is from 40 to 100 days after planting (Russet Burbank). Implications for using manure compost as an N source because of slow N release. Johnson, D. A., ed., 2008, Potato Health Management, 2nd ed., Am. Phytopath. Soc.

4 Dry petiole analysis as an N management tool Crop should be monitored throughout the season. Identifies nutrient requirements during the crucial bulking phase to maximize yield potential. Trends observed from weekly sampling of petioles assist in anticipating and detecting nutrient deficiencies.

5 Nitrate-N (NO3-N) requirements decline over growth and development period Petiole Nitrate - ppm Luxury N Level Sufficient N Level Deficient N Level Days after emergence

6 Critical petiole NO3-N levels associated with tuber initiation (TI) TI 25,000 ppm 3 wk after TI 14,000 ppm 6 wk after TI 10,000 ppm Mal Westcott, 1996, Fertilizer Facts #6, Montana State Univ.

7 Dry petiole analysis Routine use of tissue analysis is often limited because of time delays between the field sampling and laboratory analysis. A week may be necessary for oven drying, grinding, and analysis in the laboratory.

8 Rapid tissue analysis New instruments and test kits have been developed to provide instant results with fresh plant sap. A rapid test to measure NO3-N of the fresh sap allows N testing and fertilizer recommendations to be done on-site. But is the rapid test useful when organic nutrients are used as a fertilizer source?

9 Sap NO3-N concentrations of potato Closely associated with Nfertilizer rates and soil mineralizable N. Careful selection of the 4th petiole and sampling between 10 AM and 12 noon will minimize variability of the sap nitrate levels.

10 Critical petiole sap NO3-N levels for potato (D. Waterer, Univ. of Sask.)

11 Consensus on nutrient availability of compost Mineralization of organic N is expected to be low for composted manure ( 18%). Mineralization of C and N are inextricably linked, the effect of supplemental N on the mineralization rate of organic N is unknown. Phosphorus (P) availability from manure compost is high (> 70%). Potassium (K) availability from manure compost is nearly 100%.

12 Source of N (kg/ha) Field 1 Field 2 Compost N ESN Urea Ammonium Phosphate Monoammonium Phosphate Urea Ammonium Nitrate Nitrogen totals Fertilizer N

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14 Plot Design Field 1 Harvest rows Fertilizer 11 m Lab test Cardy test Compost 19.8 T ha-1 Field 2 Compost T ha Fertilizer

15 Preparation of the petiole Leaflet removal 4th fully developed leaf Petiole

16 Extraction and analysis of petiole sap Cardy meter is calibrated with certified standards Meter is recalibrated every twelve samples The battery is replaced frequently Each sample is analyzed at least in triplicate

17 T Compost Trt Petiole NO3 Field # Fertilizer Trt Petiole NO T Compost Trt Sap NO Fertilizer Trt Sap NO Petiole Sap NO3-N, mg L-1 (Cardy) Dry Petiole NO3-N, mg kg-1 ( lab analysis) Effect of fertility treatment on dry petiole and petiole sap NO3-N Days after planting Fertigation events

18 T Compost Trt Petiole NO3 Field # Fertilizer Trt Petiole NO T Compost Trt Sap NO3 Fertilizer Trt Sap NO Petiole Sap NO3-N, mg L-1 (Cardy) Dry Petiole NO3-N, mg kg-1 (lab analysis) Effect of fertility treatment on dry petiole and petiole sap NO3-N Days after planting Fertigation events

19 Correlation between NO3-N concentrations in dried petioles and petiole sap High compost rate Fertilizer Compost

20 Correlation between NO3-N concentrations in dried petioles and petiole sap Low compost rate Compost Fertilizer Upper range of the meter

21 Summary The decline in petiole NO3-N concentrations, interrupted or delayed by in-crop N applications, can be detected with the sap NO3-N test even in fertility systems using manure compost. The correlation between the petiole sap test and dry petiole test is at least as good if not better when compost is included in the fertility management plan compared to fertilizer alone.

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