Statewide Extension Projects

Transcription

1 Statewide Extension Projects Revising Soil Phosphorus Recommendations Manure Nitrogen Availability in Major Hawaiian Soils Jonathan Deenik Assistant Specialist, Soil Fertility Department of Tropical Plant and Soil Sciences

2 Using Soil Testing to Improve Fertilizer Management in Intensive Vegetable Production Systems P in plants and soils P accumulation in soils Soil P test and interpretation Basis for revising current soil P critical levels Field Trials Results of Field Trials (2005)

3 P is one of the Big 3 P essential for vigorous growth and development of reproductive parts (fruits & seeds) P often limiting in Soils

4 P Reacts in Soil

5 P Fixation in Maui Soils Paia Lahaina Kahului Kula P Fixation High Moderate Low Kihei Hana High Very High Low Kaupo

6 P Fixation in Hawaii Soils Kona Volcano Pahoa P Fixation Low High Very High

7 Soil Solution P and Plant Growth

8 Plant P Uptake

9 Importance of Residual P in Tropical Soils Wahiawa series planted to corn R.L. Fox

10 Predicting P Availability: Soil Tests What is a soil test? - a dilute extracting solution that removes plant available nutrients. - there are many extractants for P - extractant is chosen depending on soil chemical properties. - extractant does not measure fixed P - Result of soil test is the basis for fertilizer recommendation

11 Predicting P Availability: Soil Tests Soil critical level mg kg -1

12 P Accumulation in Agricultural Soils ADSC 65% in 2003

13 Current ADSC P Critical Levels Heavy Soils = mg kg -1 Light Soils = mg kg -1 A`a Land = mg kg -1 Are these values suitable for vegetable crops?

14 R.L. Fox s Vegetable Calibration Studies Sweet potato = 0.1 Soybean = 0.2 Nishimoto et al., 1977 Chinese cabbage = 0.2 Head lettuce = 0.3

15 Nishimoto et al., 1977 Cucumber = 0.2 Manoa lettuce = 0.3 Eggplant = 0.3

16 R.L. Fox s Vegetable Calibration Studies Nishimoto et al., 1977

17 Extractable Soil P for 95% Max Yield Crop Target Solution P mg L -1 Soil Critical Level Modified Truog mg kg -1 Akaka Kula Kapaa Wahiawa Waialua Sweet Potato Soybean Chinese Cabbage Head Cabbage Cucumber Eggplant Tomato Lettuce

18 Objectives 1. Characterize soil P on intensive vegetable farms. 2. Test whether crops grown on soils testing high in P respond to additional P fertilization. 3. Evaluate the suitability of the current soil P critical levels used by the University. 4. Increase farmer use of soil testing for efficient fertilizer use.

19 Cooperators 1. Oahu (Ewa series) 2. Maui (keahua and Kula series) 3. Big Island (Kikoni series) Crops: head cabbage, bush beans, manoa lettuce

20 Experimental Design Replicated field trials comparing farmer practice with 1 or more alternative fertilizer practices. i.e. 1. Farmer practice 2. Urea 3. Urea + Starter P (80 lbs/acre) Randomized complete blocks with 3 replicates

21 Sampling Soils initial + post harvest (ph + cations) Tissue 6 weeks after planting Fresh weight at harvest (above ground) Tissue whole plant at harvest

22 Ash Soils

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24 Extractable K

25 Results Ash Soil Cabbage P>F Blend Urea Mg Ca K P N Treatment Harvest P>F Blend Urea Mg Ca K P N Treatment 6 Weeks Tissue Yield

26 Results Ash Soil, Cabbage Tissue Yield (lbs acre -1 ) P>F 0.20a 2.21a 6.27a 0.60a 5.10a Urea+P 0.19a 2.33a 6.34a 0.53b 5.07a Urea 0.19a 2.17a 6.54a 0.59a 4.92a FP Mg Ca K P N Treatment P>F 0.16a 2.18a 5.24a 0.59a 3.86a Urea+P 0.16a 2.07a 5.27a 0.58a 3.80a Urea 0.15a 2.10a 5.23a 0.56a 3.87a FP Mg Ca K P N Treatment Harvest 6 Weeks

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28 Results Clay Soil, Cabbage, Low P Section Yield (lbs acre -1 ) Tissue 6 Weeks Treatment N P K Ca Mg FP 5.26a 0.65a 4.22a 1.51a 0.35a Urea 5.17a 0.52a 3.44a 1.35a 0.31a Urea+P a 3.71a 1.51a o.34a P>F Harvest Treatment N P K Ca Mg FP 3.35a 0.46a 4.11a 2.09a 0.38a Urea 3.03b 0.41a 3.40b 1.51b 0.31b Urea+P 3.24ab 0.43a 3.80a 2.00a 0.39a P>F

29 Results Clay Soil, Cabbage, High P Section Yield (lbs acre -1 ) Tissue 6 Weeks Treatment N P K Ca Mg FP 5.04a 0.63a 4.45a 1.64a 0.35a Urea 4.91a 0.61ab 4.46a 1.65a 0.35a Urea+P 4.72a 0.57b 4.13a 1.66a 0.35a P>F Harvest Treatment N P K Ca Mg FP 3.16a 0.38a 3.83a 1.89a 0.32a Urea 3.13a 0.37a 3.74a 1.94a 0.33a Urea+P 2.86b 0.36a 3.61a 1.80a 0.31a P>F

30 Results Clay Soil, Beans Fresh Bean Yield (lbs acre -1 )

31 Results Clay Soil, Manoa Lettuce Lettuce Yield (lbs acre -1 ) Tissue 6 Weeks Treatment N P K Ca Mg FP 4.49a 0.58a 7.42a 1.02a 0.44a N 4.48a 0.60a 7.22a 1.00a 0.43a P>F

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33 Results Ash Soil, Cabbage, P Rate Experiment Farmer Rate 0.8 Cabbage Fresh Wt (lbs acre -1 ) Tissue P (%) P Added (lbs acre -1 ) P Added (lbs acre -1 )

34 Results Ash Soil, Cabbage, P Rate Experiment Fresh Weight (lbs acre -1 ) Extractable P (mg kg -1 )

35 Fertilizer Costs ($ acre -1 ) Big Island Maui Big Island Maui

36 Summary Soil P ranges from 250 to 2,000+ mg kg -1. In fields where soil P > 500 mg kg -1 crops showed no response to added P. Crops grown in soils with soil P < 400 mg kg -1 show a response to added P. Indicates that current P recommendations made by UH for vegetable crops are not correct

37 Remaining Questions How do other vegetable crops respond when only N is added? Celery trial (Waimea) Onion trials (Pulehu, Omaopio, Ewa) Lettuce trial (Waimea) What is the P critical level? Is it different for the different vegetable crops? How do we effectively communicate this information?

38 Characterizing Nitrogen Mineralization and Plant N Supply from Animal Manures in Hawaii s Soils Objectives: To determine the N mineralization rates including mineralization constants (k values) for three manures (chicken, dairy, and swine) in five soils with contrasting physical and chemical properties. To determine optimum rate of manure application to satisfy crop N requirement and evaluate N release during three successive cropping cycles. To develop revised manure application recommendations for Hawaii growers.

39 Methods Objective 1: Conduct 26 week laboratory incubation. 5 Soils Representing major agricultural areas in the state: Waimea series (Haplustands) Honokaa series (Hydrudands) Wahiawa series (Haplustox) Molokai series (Eutrotorrox) Waialua series (Haplustolls). Manure Materials: Chicken, Swine, Dairy

40 Soil Chemical Properties Soil ph EC N OC P K Ca Mg Mn Fe Cu Zn dsm -1 % mg kg -1 Waimea Honokaa Molokai Wahiawa Waialua

41 Manure Chemical Properties Manure ph N OC C:N P K Ca Mg % Chicken Dairy Swine

42 300 Wahiawa Soils Alone Molokai Waialua N Mineralized (mg kg -1 ) Waimea Weeks Honokaa N Mineralized (mg kg -1 ) Weeks

43 Chicken Manure 250 Chicken Manure Wahiawa Molokai Waialua Waimea Honokaa N Mineralized (mg kg -1 ) Weeks

44 Dairy Manure 250 Dairy Manure Wahiawa Molokai Waialua Waimea Honokaa N Mineralized (mg kg -1 ) Weeks

45 Swine Manure N Mineralized (mg kg -1 ) Swine Manure Wahiawa Molokai Waialua Waimea Honokaa Weeks

46 Manure Soil % N Mineralized Chicken Wahiawa 13.9 Molokai 9.1 Waialua 11.6 Waimea 14.3 Honokaa 13.3 Composted chicken manure has a slow N mineralization rate regardless the soil

47 Manure Soil % N Mineralized Dairy Wahiawa 21.6 Molokai 15.1 Waialua 20.1 Waimea 16.5 Honokaa 16.4 Dairy manure has a slow N mineralization rate regardless the soil

48 Manure Soil % N Mineralized Swine Wahiawa 24.5 Molokai 48.8 Waialua 44.3 Waimea 27.7 Honokaa 41.2 Aged swine manure has an intermediate N mineralization rate Soil appears to make a difference

49 Ongoing Work Completed incubations for sunn hemp, fish/blood meal, and Mac Nut husk Installing field experiment phase of manure project Preparing extension/journal publications