Bio-stimulants in Sub-tropical crops. Bram Snijder Afrupro Exporters

Transcription

1 Bio-stimulants in Sub-tropical crops Bram Snijder Afrupro Exporters

2 Aim of the talk Supply some back ground on the Subtropical industry Current status with regard to fertiliser recommendation Work done on Bio-stimulation/control Future research needed

3 Introduction Subtropical industry small in comparison to the deciduous industry but expanding Excludes Citrus Industry Exported as exotic fruit into niche markets Local market still relatively small and often exclusive In this talk we concentrate on the 4 industries which fall under the Sub-trop umbrella

4 Introduction

5 Introduction Crops mostly grown in North-Eastern South Africa Limpopo 41% of area, followed by Mpumalanga 35% KZN growing area especially for the late market opportunity 4 grower association avocado = strongest in terms of its member cohesion Always been voluntary organisations

6 Intro Avocados Originated in the central American Forests from sea level up to 1500m altitude Under-story tree in rain forest Its drive is to reach sunlight = strong focus on growth not fruiting Very quickly irradiance saturated Rapid system shutdown in warm sunny conditions

7 Intro - Avocado Initial growing system is extensive Average tree age about 15 years+ Low tree density (100 plants/ha) Large trees low productivity/economics Low yield Fair percentage of dry-land (20%) Little cultivar development Low research budget

8 Intro - Avocados Newer plantings more intensive Newer cultivars Higher densities (up to 400 plants/ha) Better yields Smaller trees (better productivity/economics) Research started into protective growing in conjunction with 2 universities

9 Intro - Litchis Originated from Tropical South - China Forest tree with low yield potential More tropical climates Climate marginal in South Africa New cultivars being imported from Israel and Australia Extremely small research budget

10 Intro - Litchis Trees are grown extensively ( trees/ha) Extremely large until recently Pruning systems introduced Yield improvements through flush control in autumn Yields are very climate sensitive need either cold or drought stress ± April

11 Intro - Mango Originated from India North-eastern areas in the foothills of the Himalayas Wide climatic adaptations Grown mostly for local market and processing Quality issues are largest problem

12 Intro - Mango Grown more intensively (800 trees/ha) Better yields/ha than the other three crops Prefers drier climates for yield and quality(hoedspruit/komatipoort) Related to Marula and Cashew nuts Small research budget Statuary levy system on processed fruit

13 Intro Macadamia nuts Originated from Australian rainforests on the east coast of that continent Many different species found Some inter specific crosses found In SA - large industry 2 nd largest in the world Mostly export orientated Fastest growing industry in the sub-tropical regions of Africa and China.

14 Intro - Macs More intense growing systems (up to 600 trees/ha) Large trees nuts drop naturally in most cases Insects most important yield loss factor Newer trend to keep trees smaller better spraying penetration Good research budget but small percentage of paying members

15 Intro Botanical aspects Mostly forest originating trees Leaves have adapted to this Thick cuticula and small number of stomata Evergreens Leaf ages fast small amount physiological active. Photosynthesis and transpiration rates are hampered by high light saturation rates Faster photo saturation point reached (around 08h00)

16 Intro Botanical aspects Root systems have also adapted Extensive shallow root systems Sensitive to flooding in most cases Needs lots of oxygen to grow Compost loving Stress conditions kills feeder roots off Winter Photo inhibition reduces root capability (i.e. no water and mineral uptake)

17 Current fertiliser practices Mostly very rough guidelines i.e. 2-3 times/year large quantities Not properly based on the tree phenology Little work done i.t.o. nutrients vs yield and quality Focus on standard N, P, K;little on other elements Boron received some status

18 Current practices Mostly low feeders of N, P, K correct? Fertigation practises very limited Application often done during rainy season i.e. not necessary the most optimal time for yield and quality Root growth cycles also mostly linked with rainy season and soil temperatures

19 Current recommendations Avocado Litchi Mango Macadamia Nitrogen 9.2 kg/ton 1000 g/tree 420 g/tree 600 g/tree Phosphate Potassium Calcium 4.6??? Magnesium 2.2???

20 Micro nutrients Currently very little is known Boron has been studied in conjunction with Fruit set Limited work done on Zinc with regard to leaf size and fruit retention Other micro nutrients are thought to be of little influence in sub-ropical crops Thought to be part of normal fertiliser as part of filler material

21 Foliar application Leaf anatomy = little uptake For salt-formulations might be true Newer formulations with amino acid / organic chelation?? Little influence on leaf mineral content Other factors??

22 Foliar applications Timing is critical mostly when new flushes develop before leaf hardening as this is thought to be the most absorbent time of the year Ca and B have been stated to be beneficial especially for quality Sometimes under stress conditions (drought, heat or disease) Zn, K and N Other chemicals?

23 Avocado main issues Heat stress during flowering Low yield and fruit size important Fruit drop extensive in some years Fruit quality most important issues Greypulp, Pulp spot Lenticell damage

24 Avocados - recommendations Heat stress limited research results available Low yield Boron applications during flowering Impact low?? Difficult to measure Add N and P Organic chelated products Fruit set and size (PGR) Paclobutrazole/Uniconazole together with phosphates

25 Avocados - recommendations Fruit drop Applications of Zn and N Fruit quality Very much calcium related Soil application during flowering Foliar applications include B Organic chelated products

26 Humic and Fulvic acids Becoming standard practice in deciduous fruit industries Sub-tropical industry very behind Blends contain some fulvic acids for foliar sprays Soil applied humic acids especially together with microbial solutions Mixed results little controls

27 Future research Much needed field of research to intensify production Extensive growing systems results are debatable Very mixed results under different growing conditions However intensive systems becoming more uniform and better managed

28 Future research Bio-stimulation research should focus on: 1. Stress relieve during flowering and fruit set 2. Increased production 3. Decreased fruit drop 4. Fruit size improvement 5. Fruit quality improvement

29 Thank you for attention and the opportunity to be here