Relationship between soil alteration index three (AI3), soil organic matter and tree performance in a ‘Cripps Pink’/M7 apple orchard

Figures & data

Table 1: Conventional (CON) and organic (ORG) soil surface management treatments applied in a ‘Cripps pink’/M7 trial orchard

Treatment	Work row		Tree row (drip line to drip line)
	Tree dormant	Tree active
T1 (CON)	Weed cover	Cover mown, natural die-back in summer	Chemical weed control^Table Footnotea + inorganic N^Table Footnoteb
T2 (CON)	Cover crop^Table Footnotec	Cover crop^Table Footnotec, chemical weed control in spring^Table Footnotea	Chemical weed control^Table Footnotea + inorganic N^Table Footnoteb
T3 (ORG)		Permanent straw mulch^Table Footnoted, hand weeded	(Compost + mulch)^Table Footnotee; hand weeded
T4 (ORG)	Cover crop^Table Footnotec	Cover crop^Table Footnotec, mown, natural die-back in summer	(Compost + mulch)^Table Footnotee + compost tea^Table Footnotef; hand weeded
T5 (ORG)	Weed cover	Cover mown, natural die-back in summer	(Compost + mulch)^Table Footnotee; hand weeded

a Roundup 360SC^® applied at 5 litres ha^-1 (3%) in September and January

b Nitrogen as limestone ammonium nitrate (LAN) applied at full bloom, six weeks after full bloom and after harvest at rates of 9.2 g N, 5.2 g N and 18.0 g N tree^-1, respectively, in seasons 2003/04 to 2007/08. Applied after harvest only, at 18.0 g N tree^-1, in 2008/09 and 2009/10. Applied to the tree row in a continuous strip 100 cm wide

c Rye (Secale cereale L. cv. Henog) and oats (Avena sativa L. cv. Pallinup) planted in tilled soil (0-10 cm) after leaf senescence in alternate seasons. Nitrogen (as LAN) applied to the cover crops and weed covers at 14 kg N ha^-1 in June

d Wheat or oat straw (mulch) applied as a 5 cm layer in a continuous strip, c. 100 cm wide, along the tree row. Mulch applied at 3.2 kg straw tree^-1. Work rows covered with a 5 cm layer of straw mulch. Mulches replenished annually in October

e Compost applied at 20 kg per tree^-1 (128 g N, 3.7 g P, 6.3 g K tree^-1) in spring and autumn 2003/04, 10 kg tree^-1 in spring and autumn 2004/05 to 2006/07, and 10 kg tree^-1 in spring 2008 and 2009. Spread in a continuous strip, c. 1 m wide, along the tree row. Covered with a 5 cm layer (c. 3.2 kg per tree^-1) of wheat or oat straw (mulch). Mulch reapplied annually, in October

f Compost tea (aerated, aqueous, microbial digest) surface-applied around each tree at 1 litre tree^-1 per four-week interval from full bloom to leaf senescence. Principal components (mg ml^-1): P, 7.5; K, 190; Ca, 51; Mg, 34.6; Na, 163. Nitrogen: 0.06%

Table 2: Effect of conventional (CON) and organic (ORG) management on soil alteration index three (AI3), and on soil organic matter (SOM) content, stem circumference, yield, yield efficiency (kg cm^-2 stem cross-sectional area) in a ‘Cripps pink’/M7 apple orchard. Values in the same column followed by the same letter do not differ significantly at p = 0.05

Treatment	SOM 2003-2010 (%)^Table Footnote1	Increase in stem circumference 2006-2010 (cm)^Table Footnote2	Increase in stem circumference 2003-2010 (cm)^Table Footnote2	Increase in stem circumference 2006-2010 (%)^Table Footnote2	Average yield 2006-2010 (t ha^-1)^Table Footnote2	Yield efficiency 2006-2010 (kg cm^-2)^Table Footnote2	AI3 September 2007-2010	AI3 January2008-2011
T1 (CON)	1.06^d	12.60^b	6.3^a	11.5^b	38.71^a	0.386^a	-23^ab	-47^ab
T2 (CON)	2.03^cd	12.58^b	6.5^a	12.6^ab	32.59^ab	0.363^a	-20^a	-43^a
T3 (ORG)	3.22^ab	17.15^a	8.0^a	15.0^a	29.30^bc	0.218^b	-33^bc	-51^b
T4 (ORG)	3.54^a	16.05^a	7.6^a	14.8^a	22.51^c	0.186^b	-36^c	-51^b
T5 (ORG)	3.45^a	15.90^a	6.8^a	13.9^ab	21.74^c	0.168^b	-36^c	-51^b

1 Tree row including drip zone. Data of Wooldridge et al. (2013a)

2 Data of Wooldridge et al. (2013b)

Table 3: Pearson correlation coefficients (r) between soil alteration index three (AI3), soil organic matter (SOM) content and plant performance parameters and in a ‘Cripps pink’/M7 apple orchard in September 2006 to 20010 and January 2007 to 2011 (n = 20)

Parameters correlated	r	p
September AI3 x January AI3	0.6069	0.0045
September SOM x January SOM	0.9847	<0.0001
September AI3 x September SOM	-0.7761	<0.0001
January AI3 x January SOM	-0.4613	0.0406
September AI3 x stem circumference increase	-0.1760	0.4580
January AI3 x stem circcumference increase	-0.1027	0.6667
September AI3 x percentage increase in stem circumference	-0.0480	0.5733
January AI3 x percentage increase in stem circumference	-0.0515	0.5458
September AI3 x yield	0.5110	0.0213
January AI3 x yield	0.2416	0.3049
September AI3 x yield efficiency	0.6565	0.0017
January AI3 x yield efficiency	0.4160	0.0681
September SOM x yield	-0.5885	0.0063
January SOM x yield	-0.6151	0.0039
September SOM x yield efficiency	-0.8296	<0.0001
January SOM x yield efficiency	-0.8516	<0.0001
Yield x yield efficiency	0.8175	<0.0001

Wooldridge J, Fourie J, Joubert M. 2013a. Effects of soil surface management practices on soil and tree parameters in a ‘Cripps pink’/M7 apple orchard 1: mineral nutrition. South African Journal of Plant and Soil 30: 163–170.

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Wooldridge J, Fourie J, Joubert M. 2013b. Effects of soil surface management practices on soil and tree parameters in a ‘Cripps pink’/M7 apple orchard 2: tree performance and root distribution. South African Journal of Plant and Soil 30: 171–177.

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