Copyright is owned by the Author of the thesis. Permission is given for a copy to be downloaded by an individual for the purpose of research and private study only. The thesis may not be reproduced elsewhere without the permission of the Author. Kiwifruit (Actinidia spp.) vine and fruit responses to nitrogen fertiliser applied to the soil or leaves A thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Fruit Science at Massey University Palmerston North, New Zealand Allan Robert Morton 2013 i Abstract Dry matter concentration (DM%) of the fruit is a primary indicator of quality for kiwifruit (Actinidia spp.), lower levels being associated with inferior tasting fruit. Carbohydrates and particularly starch, are the main component of dry matter in the fruit of Actinidia spp. In plants, N fertilisation can reduce carbohydrate levels and increase succulence. Therefore high levels of N fertilisation could reduce fruit DM% by reducing its dry matter accumulation and increasing its water content. High rates of N fertiliser applied to kiwifruit vines (A. deliciosa) over four seasons tended to produce larger fruit (5% heavier on average over the four seasons) mainly due to increased water content with less effect on total dry matter contents. Consequently DM% was reduced from an average over the four seasons of 16.1% in the unfertilised (control vines) to 15.6% in fruit from the N fertilised vines. However, vegetative vigour in terms of the weight of shoots was increased by up to 150% by N fertiliser. Biostimulants applied as foliar sprays and surplus water supplied to the soil appeared to alter the balance between dry matter and water accumulation in the fruit in a similar way to soil- applied N fertiliser. It is concluded that increases in fruit size induced by N fertilisation, biostimulants, surplus water, and even girdling are at least partly due to the creation of increased hydraulic gradients between the vine and fruit leading to increased water uptake by the fruit. Other effects on fruit of high rates of soil-applied N fertiliser included reduced ascorbic acid, oxalate, and epidermal phenolics. Reductions in levels of these compounds and the generally increased succulence of N fertilised vines may increase the susceptibility of the vines to pests and diseases. In contrast to soil-applied N, foliar sprays of N applied during early fruit development stages increased fruit growth with no apparent effect on vegetative vigour. Aqueous solutions (1% w/v) of both urea and potassium nitrate were effective forms of N for foliar application and could increase fruit fresh weight by between 6 and 10% depending on the season and number of applications. It is estimated that the use of foliar- applied N during early fruit development could represent an increase in crop value of between $3600 and $15,000 per hectare depending on size and yield. Foliar-applied N shows promise as an alternative way to manage the N nutrition of kiwifruit with favourable effects on fruit quality since dry matter accumulation in fruit tended to increase proportionately with increased water uptake. Foliar application of N can also avoid some of the adverse environmental effects associated with the soil application of soluble N fertilisers. ii iii Acknowledgements Thanks are given to my supervisors Dr David Woolley and Dr Huub Kerckhoffs for their patient and helpful reviewing of the manuscripts. I also acknowledge David Woolley and Dr Tessa Mills for support and guidance provided throughout the years of field and laboratory work spent gathering the material for the thesis. Numerous other people have also given friendly and helpful assistance including staff at the Fruit Crops Unit at Massey University. I am also grateful and somewhat surprised at the continuing patience of Ian Furkett and others in the soil laboratory, and Chris Rawlingson and others in the Horticultural Science laboratories at Massey University in their patient overseeing of my chemical analyses. Helpful encouragement to complete the thesis was also received from Associate Professor Hossein Behboudian, Professor Mike Hedley, and Alistair Mowatt of Zespri. I am also grateful to Zespri (NZ) Ltd and Massey University for providing the funding and opportunity to undertake this project. Special thanks are given to Dr Maysoon Rassam for her time and assistance, which enabled me to complete the oxalate and ascorbic acid analysis at Crop and Food’s Mt Albert Research Centre in Auckland. iv v List of Abbreviations BK CPPU CV% DAFB DPBB DM% DW EC FC FN1, FN2 FW HATS HN HN+SF LN LN+SF LNF MN MNF N N1-N4 NAA NO3 - NR NUE Benefit Kiwi® N-(2-chloro-4-pyridyl)-N'-phenylurea coefficient of variation days after full bloom days ‘post’ or after bud break dry matter concentration dry weight electrical conductivity field capacity foliar-applied N at time 1 or time 2, abbreviation used in Experiment 1 in Chapter 6. fresh weight high affinity transport system high nitrogen (high rates of N fertiliser) treatment high nitrogen plus spring-applied fertiliser treatment low nitrogen (nil N fertiliser) treatment low nitrogen plus spring-applied fertiliser (Chapter 3) low nitrogen plus foliar urea treatment (Chapter 7) moderate rates of N fertiliser treatment (Chapter 7) moderate rates of N fertiliser plus foliar urea treatment (Chapter 7) nitrogen potassium nitrate (foliar treatments at times 1 to 4) 1-Naphthaleneacetic acid nitrate nitrate reduction nitrogen use efficiency New Zealand daylight saving time vi NZDST Pn SSC SSFDM% SOM SW TA U1 – U4 UW W fruit leaf s vine photosynthesis soluble solids content soluble solids as percentage of DM% soil organic matter surplus water treatment (Chapter 8) titratable acidity urea (foliar treatments at times 1 to 4) un-watered (control) treatment (Chapter 8) water fruit water potential leaf water potential osmotic potential vine water potential vii Table of Contents Abstract ................................................................................................................................ i Acknowledgements ................................................................................................................... iii List of Abbreviations................................................................................................................. iv Chapter 1 Introduction and Literature Review ...................................................................... 1 Chapter 2 Materials and Methods........................................................................................ 83 Chapter 3 Effects of nitrate fertiliser applied to the roots on fruit and vegetative characteristics of ‘Hort16A’ and ‘Hayward’ kiwifruit ....................................... 91 Chapter 4 Effects of nitrate fertiliser applied to the roots on some physical and biochemical quality attributes of ‘Hayward’ and ‘Hort16A’ fruit .................... 143 Chapter 5 The response of ‘Hort16A’ fruit to foliar applications of nitrogen and a proprietary biostimulant.................................................................................... 175 Chapter 6 Response of ‘Hayward’ kiwifruit to foliar applications of nitrogen, CPPU, and seaweed ...................................................................................................... 201 Chapter 7 Effects of foliar-applied urea on fruit and vegetative growth in ‘Hayward’ kiwifruit vines differing in N status .................................................................. 239 Chapter 8 Manipulation of fruit water and dry matter content by treatments applied during early and late stages of fruit development in ‘Hayward’ kiwifruit........ 255 Chapter 9 General discussion ............................................................................................ 275 References ........................................................................................................................... 297 Appendices ........................................................................................................................... 335 viii CHAPTER 1 1 Contents 1. Introduction and Literature review ........................................................................1 1.1 Introduction...............................................................................................................3 1.2 The regulation of dry matter and water contents in the kiwifruit (Actinidia spp.) berry during its growth....................................................................................1 1.2.1 Introduction............................................................................................................5 1.2.2 Fruit development ..................................................................................................6 1.2.3 Fruit water content ...............................................................................................11 1.2.4 Dry matter ............................................................................................................17 1.2.5 Summary and conclusions ...................................................................................21 1.3 Effects of nitrogen fertiliser on kiwifruit vegetative and fruit growth, and fruit quality. ...................................................................................................................23 1.3.1 Introduction..........................................................................................................23 1.3.2 Nitrogen supply....................................................................................................26 1.3.3 Vine demand (uptake)..........................................................................................28 1.3.4 Nitrate ..................................................................................................................31 1.3.5 Uptake and vegetative response...........................................................................35 1.3.6 Yield.....................................................................................................................36 1.3.7 Fruit size...............................................................................................................42 1.3.8 Dry matter ............................................................................................................44 1.3.9 Starch and soluble solids......................................................................................47 1.3.10 Oxalate ...............................................................................................................48 1.3.11 Acidity................................................................................................................49 1.3.12 Phenolics ............................................................................................................51 1.3.13 Variability ..........................................................................................................52 1.3.14 Fruit firmness .....................................................................................................53 1.2.15 Conclusions........................................................................................................54 1.4 Foliar-applied nitrogen............................................................................................55 1.4.1 Introduction..........................................................................................................55 1.4.2 Forms of foliar N .................................................................................................57 1.4.3 Use of foliar nitrogen in kiwifruit. .......................................................................58 1.4.4 Effect of foliar N on other fruits ..........................................................................60 1.4.5 Effect of foliar N on vegetative vigour ................................................................62 1.4.6 Absorption of foliar-applied N.............................................................................63 1.4.7 Surfactants............................................................................................................68 1.4.8 Effect of foliar-applied N on leaf N content ........................................................70 1.4.9 Assimilation and translocation.............................................................................71 1.4.10 Phytotoxicity ......................................................................................................73 1.4.11 Conclusion .........................................................................................................78 1.5 Overall conclusions.................................................................................................79 1.6 Problem statement...................................................................................................80 1.7 Objectives ...............................................................................................................80 CHAPTER 1 2 List of Tables Table 1.1 Effect of plant growth regulators applied during Stage 1 of fruit growth on fruit FW (g), DM%, DW (g), and water (g) at harvest on two kiwifruit cultivars. .................................................................................13 Table 1.2 Relative change in fruit dry matter concentration (DM%), water and dry weight (DW) content between fully irrigated and deficit irrigation treatments (see text for details) in apples and peppers. ................................14 Table 1.3 Examples of annual fertiliser nutrient inputs for different orchards with estimated quantities removed with harvested crop (in parenthesis)...................................................................................................23 Table 1.4 Effect of the amount of urea-N applied annually on yield and vegetative growth of olives (average of 1994-1999) (from Fernandez- Escobar et al. 2002). .....................................................................................25 Table 1.5 Effect of increasing nitrogen supply (NH4NO3) on dry matter production and composition of ryegrass (from Marschner 2002). ...............47 List of Figures Figure 1.1 Changes during fruit development in (A) fresh weight (FW g), dry weight (DW g), and (B) FW and DM% of Actinidia deliciosa, with fruit developmental stages (solid vertical divisions) and suggested revised delineation of Stage 1 and 2 (dashed vertical line) (adapted from Richardson and Currie (2007) and modified according to various sources as given in text). .................................................................8 Figure 1.2 Percentage difference compared to control (no girdle) in FW, DM%, DW and water contents in fruit (water/fruit) at harvest from vines trunk girdled at different times during Stage 1 (weeks 0- 6) or Stage 2 (weeks 8 to 16) of fruit growth (adapted from Currie and Richardson 2007). ......................................................................................18 Figure 1.3 Effects of different nitrogen fertiliser rates on kiwifruit yield at high and low vine planting densities and in four seasons (after Buwalda et al. 1990). ....................................................................................................39 Figure 1.4 Biennial trends in kiwifruit yields; 1973-1977 from Davison (1990); 1986-1989 from Buwalda et al. 1990). ......................................................40 Figure 1.5 Kiwifruit yields (kg/vine) over 6 years at 4 different nitrogen fertilisation rates (from Vizzotto et al. 1999).............................................42