Results from the Lund/Arpaia nitrogen study: What did we learn?

Transcription

1 Results from the Lund/Arpaia nitrogen study: What did we learn?

2 Nitrogen Management in itrus under Low Volume Irrigation L. Lund, M. L. Arpaia,. J. orbett

3 OBJETIVES Evaluate leaching losses of N and fruit quality in relation to Applied nitrogen amounts Foliar versus soil applied nitrogen Timing Determine the effectiveness of various N levels methods of application on maintaining optimal N levels in trees

4 Why were we interested in nitrate leaching losses?

5 Groundwater is essential to alifornia, and nitrate is one of the state s most widespread groundwater contaminants. Nitrate in groundwater is principally a by-product of nitrogen use, a key input to agricultural production. However, too much intake of nitrate through drinking water can harm human health. Harter et al., 0

6 Why were we interested in fruit quality?

7 Plant Nutrition Nitrogen (N) fertilization (rate and timing) likely has the greatest impact on A citrus quality Most A soils are adequately supplied with phosphorus (P) and potassium (K) Adequate P and K are required for high fruit quality particularly the rind

8 High Nitrogen Delayed coloring Thicker rind oarser rind Increased staining of navel orange Increased valencia re-greening Interacts with other nutrients in terms of fruit quality

9 P low N check P low N high P adequate N low P adequate N high Effects of nitrogen and phosphorus on navel orange fruit quality Embelton and Jones, Yr 6 of 0 yr study

10 Results of our research

11 Background information Much work already conducted on the influence of nitrogen in alifornia and elsewhere Nitrogen essential for yield and overall tree health itrus is able to absorb foliar applied N; soil nitrate can be reduced N applied at targeted times can influence yield, fruit set and fruit size

12 EXPERIMENTAL DESIGN Main Site - Exeter Treatments = 5, Replications = 4» Foliar only -, or 4 applications» Soil only -, or continuous» ombination» Rates vary from 0 to.5 lb N/tree/yr Satellite Sites - Orange ove, Woodlake Treatments = 6» Soil only - or cont. - rates to lb N/tree/yr» ombination -.5 lb N/tree/yr

13 Type of Data ollected Differential application of N treatments All sites harvested for fruit quality analysis Exeter Site - Lindcove RE Packline/storage at KA Woodlake and Orange ove Sites - Harvested and run over commercial packline and storage at KA Leaf analysis and monitoring of fruit color break in Fall; canopy size and trunk girth Soil Leachate sampling on regular basis

14 Leaf Analysis

15 LEAF N vs. N APPLIED LEAF NITROGEN ONTENT - % YEAR NITROGEN APPLIED - LBS/TREE

16 GF - LEAF NITROGEN LEAF NITROGEN (%) TOTAL N APPLIED ANNUALLY (LBS/TREE) 4 Method of Application Foliar only Soil only Foliar and soil ontrol 4 LEAF NITROGEN (%) TOTAL N APPLIED ANNUALLY (LBS/TREE) 4 4 Method of Application Foliar only Soil only Foliar and soil ontrol

17 What does the data tell us? Took approximately 3 years to establish differential leaf analysis Over last three years, trend toward foliar/soil combination to have highest leaf N. This affect clearest in 00. At all sites the relationship of treatment to leaf N is evident.

18 Sampling of Soil Solutions Soil solutions extracted just below root zone by applying a vacuum to a porous ceramic cup.

19 GF - NO 3 -N (SS) vs. N APPLIED MEAN NITRATE-N IN SS (MG/L) Method of Application Foliar only Soil only Foliar and soil ontrol TOTAL N APPLIED ANNUALLY (LBS/TREE) 4 4

20 GF - NO 3 -N (SS) vs. N APPLIED MEAN NITRATE-N IN SS (MG/L) Method of Application Foliar only Soil only Foliar and soil ontrol TOTAL N APPLIED ANNUALLY (LBS/TREE) 4 4 MEAN NITRATE-N IN SS (MG/L) Method of Application Foliar only Soil only Foliar and soil ontrol N SOIL APPLIED ANNUALLY (LBS/TREE)

21 GF - SS vs. SOIL EXTRAT MEAN NITRATE-N IN SS (MG/L) Method of Application Foliar only Soil only Foliar and soil ontrol N SOIL APPLIED ANNUALLY (LBS/TREE) NITRATE (SS) BY SOIL EXTRAT (MG/L) Method of Application Foliar only Soil only Foliar and soil ontrol N SOIL APPLIED ANNUALLY (LBS/TREE)

22 What does the data tell us? Foliar applied nitrogen results in less groundwater nitrate Relationship between the amount of applied N and groundwater nitrate Timing of application is less clear Trends at all sites are similar

23 Yield and Fruit Size

24 YIELDS FOR VARIOUS YEARS YIELD (lbs/plot) TREATMENT

25 UMULATIVE YIELD,000 umulative Yield per tree (lb/tree),900,800,700,600,500,400,300,00 Foliar only Soil only Foliar and soil ontrol NITROGEN APPLIED - LBS/TREE

26 What does the data tell us? Maximum yield attained with ~ to.5 lb N/tree Foliar N only tends to have lower yield Size distribution not greatly influenced by treatment More difficult to draw conclusions from yield effects at other sites

27 Fruit Quality

28 Puff/rease Evaluations North Side of Tree Incidence and severity of ontree puff/crease evaluated in 000 (3/4-3/3) and 00 (/7 - /8) prior to harvest. 0-4 scale 0 = 0%; = <5%; = <50%; 3 = < 75%; 4 = 00% of fruit surface 50 fruit on north side; chest height

29 What does the data tell us? No large differences detected in the incidence or severity of puff/crease in years of data collection.

30 PEEL THIKNESS Avg of Peel Thickness (mm) Foliar only Soil only Foliar and soil ontrol NITROGEN APPLIED - LBS/TREE

31 PEEL FIRMNESS - 00 AVERAGE FRUIT SIZE Foliar only Soil only Foliar and soil ontrol NITROGEN APPLIED - LBS/TREE

32 Other Fruit Quality Measurements Peel Texture, Peel olor Decay following storage Physiological Disorders following storage Storage Regime 4 days at 4F followed by days at 55F followed by 7 days at 68F

33 What does the data tell us? Increasing N application results in a thicker peel Increasing N application results in softer peel at harvest Other effects on quality inconsistent Method of application does not have a great influence on trend

34 Overall Summary Increasing N results in increasing NO 3 -N below root zone Method of application can influence this Maximum yield, less NO 3 -N below root zone with combination of foliar and soil applied Peel thickness increases, peel firmness decreases with increasing N No other consistent differences in fruit quality were detected following storage.

35 Project Support itrus Research Board (66%) and DFA-FREP (33%); RB (00%) Growers cooperators: Griffith Farms (Exeter), Harold Shawl and Sons (Woodlake), D. W. Ketscher Trust (Orange ove) and Highland Properties (Porterville) Packline Operations: U-LRE, Baird and Neece, Harding and Leggett, Inc., Klink itrus Association, SunTreat) Set-up of satellite sites and coordination with commercial packers: Sunkist Growers Additional Support: Bowsmith, Inc., Fruit Growers Supply ompany, Mazzie Injector orporation, Midstate Laboratory LL, Maxijet orporation and UAP WEST (urea)

36 Thank you for your attention