ISHS Plum and Prune Symposium; Palermo, Italy The Effect of Foliar Fertilization with Potassium and Magnesium on Fruit Quality in Plums ( Prunus domestica L.) Eivind Vangdal, Sigrid Flatland and Ingvild Mehl Bioforsk Vest Ullensvang, Norway

ISHS Plum and Prune Symposium; Palermo, Italy This presentation includes: Why use foliar fertilization Present status of major nutrients in plum and present recommendations for foliar fertilization in plums in Norway Results from field experiments Conclusions

ISHS Plum and Prune Symposium; Palermo, Italy Why use foliar fertilization? Strong focus on fruit quality Good foliar fertilizers are available Are fruit trees in high density orchards able to get the nutritients needed through their roots for optimum fruit quality?

ISHS Plum and Prune Symposium; Palermo, Italy Standard fertilization in plums in Norway: N-P-K mineral fertilizer on the soil in the spring Contains some calcium and magnesium and trace elements like Manganese, Boron, Zink etc.

5 Leaf analysis of plums: ElementRecommended range Average in field experiment Nirogen*2,3 – 2,82,37 Phosphorus*0,15 – 0,30,24 Potassium*2,2 – 2,82,59 Calcium*2,0 – 3,02,22 Magnesium*0,25 – 0,400,31 Boron**20 – 50 Manganese**30 – 60 Zink** *) Per cent of DM; **)ppm of DM

ISHS Plum and Prune Symposium; Palermo, Italy Standard fertilization in plums in Norway: N-P-K mineral fertilizer ( or ) on the soil in the spring Foliar fertilization: –Calcium (every second week from two weeks after petal fall until 2 weeks prior to estimated harvest date) –Boron (once after harvest, once two weeks prior to flowering –Nirogen (urea after harvest)

ISHS Plum and Prune Symposium; Palermo, Italy Field experiment with foliar fertilization with Mg and K A: Foliar fertilization programme with N, P, K, Ca, Mg, Cu, S, B, Mn, Zn (Reduced N-P-K on the ground)

StadiumweekNPCaOther nutrients D / kg urea 1 kg Cu E2 / kg urea 1 kg MAP2 kg S + 1 kg Solubor End of flowering 211 kg urea 1 kg MAP2 kg S + 5 kg MgSO 4 After flowering 241 kg urea 1 kg MAP2,5 kg CaCl 2 0,5 l Mantrac + 0,2 l Zintrac 272,5 kg CaCl 2 302,5 kg CaCl kg MKP 332,5 kg CaCl 2 Post- harvest 385 kg urea 1 kg MAP5 kg MgSO 4 + 0,5 l Mantrac 0,2 l Zintrac + 1 kg Solubor Foliar fertilization programme:

ISHS Plum and Prune Symposium; Palermo, Italy Field experiment with foliar fertilization with Mg and K A: Foliar fertilization programme with N, P, K, Ca, Mg etc. (in additon to N-P-K on the ground) B: As A + 2 x 5 kg MgSO 4 (week 24 and 27) C: As A + 2 x 3 kg MKP (week 29 and 32) D: As A + both Mg and K as in C and D Cultivars: Avalon, Excalibur and Reeves

Results: yield, fruit size and colour Yield (tons/ha) Fruit size (g) Ground colour Blush clour Control18,4554,85,0 + 2 x Mg23,7565,24,9 + 2 x K25,7544,65,1 + 2 x both Mg and K 18,9514,44,6 P-valuen.s.

Results: internal quality factors FirmnessSoluble solids content Titratable acidity SSC: acidity ratio Control7312,31,269, x Mg7312,11,269, x K7412,11,269, x both Mg and K 7412,31,289,61 P-valuen.s.

Results: leaf analysis NPKMgCa Control2,370,252,560,322, x Mg2,360,222,50,322, x K2,360,232,720,302, x both Mg and K 2,310,242,660,322,25

Results: fruit analysis NPKMgCa Control0,740,151,330, x Mg0,740,150,980,0700, x K0,770,131,230,0430, x both Mg and K 0,780,161,230,0560,107

Results: yield, fruit size and colour Yield (tons/ha) Fruit size (g) Ground colour Blush clour Control16,1416,25,5 Foliar fertilizing programme 19,2395,55,3

Results: internal quality factors FirmnessSoluble solids content Titratable acidity SSC: acidity ratio Control6311,31,418,01 Foliar fertilizing programme 6511,11,427,82

Results: fruit analysis NPKMgCa Control0,830,161,330, Foliar fertilizing programme 0,990,110,990,0450,090

ISHS Plum and Prune Symposium; Palermo, Italy Concluding remarks: The results shown in this presentations do not indicate strong effects of foliar application with Magnesium and Potassium Previous research and observations show good effects of foliar applications of Calcium, Boron (and in some situations) Nitrogen The fieled experiment with foliar fertilization with Mg and K will be repeated this year including studies of effects on shelf life of plums

Thank you for your attention!