Wheat and Lupin Potassium Responses

1. Lake Bolac Trial details

Location name: Kargoon (property), Lake Bolac (town)
Spatial co-ordinates: -37.792783 (latitude), 142.616667 (longitude)
Field name: Paddock 7
Farmer name: Peter McInnes
Crop management: Ed H. and Corinne Celestina (Southern Farming Systems)
Laboratory analysis: Graeme Poile (Wagga Wagga Agricultural Institute, NSW DPI)
Nutrient of interest: Potassium (K)
Experimental design: Randomised complete block design with 4 replicates
Treatment levels: 4 (K0 = control, K1 = 25 kg K/ ha, K2 = 50 kg K/ ha, K3 = 100 kg K/ ha
Fertiliser applied: KCl
Crop types: wheat (Kellalac); lupins (Jindalee)
Sowing rate: 80 kg/ha (wheat), 75 kg/ha (lupins)
Rainfall: (growing season – April-October - long-term average)
(growing season – April-October – 2013)
decile
Date crop sown: 14/05/2013
Date crop harvested: 13/01/2014

2. Field history information

Trial site soil characterisation. Basic soil chemical properties at Lake Bolac trial site

Horizon	Depth (cm)	pH (CaCl2)	EC (µS/cm)	OC (%)	Exchangeable cations Ca Mg K Na (cmol(+)/kg )				Colwell P (mg/ kg)	TBK (mg/kg)
A	0-10	5.47	65	1.54	4.86	0.63	0.15	0.03	22	77.3
A	10-20	4.98	53	0.68	2.00	0.36	0.14	0.02	12	70.0
B1	35-50	5.08	74	0.72	4.11	2.84	0.27	0.12	4	123.7
B2	50-100	4.73	46	0.22	0.77	4.81	0.11	0.23	2	57.0

Basic soil physical properties at Lake Bolac trial site

Horizon	Depth (cm)	Bulk density (g/ cm3)	Clay	Sand	Silt
A	0-10	1.29
A	10-20	1.61
B	35-50	-
B	50-100	-

Clay mineralogy content (percent by weight) of the soil at Lake Bolac trial site^A

Horizon	Depth (cm)	Quartz	Kaolin	Goethite	Smectite	Albite
A	0-10	87	10	1		1
A	10-20	90	7	1		1
B1	20-30	14	77	6	1
B2	30-100	8	84	6	1

^A Microcline/ orthoclase, anatase and hematite were present at or less than one percent.

Australian Soil Classification
Yellow Kurosol (Great Group = Mesotrophic; Subgroup = Mottled)


3. Soils data (at the trial plot scale)
Soil samples were taken from each plot prior to sowing to provide an assessment of the initial soil potassium status.

Soil sampling depth(s): 0-10, 10-20, 20-30 (cm)
Soil tests measured exchangeable K, tetra-phenyl borate potassium (TBK).

Soil test results

There was no significant difference found in the exchangeable K or TBK for the 0-10 cm depth between the plots across the trial. The mean for exchangeable K was 72 (mg/ kg) and the mean for TBK was 92 (mg/ kg). A non-significant and increasing north:south trend was detected across the plots, but this was considered too have had an excessive effect on the applied treatments. For the 10-20 cm depth the exchangeable K was 68 (mg/ kg) and the mean for TBK was 71 (mg/ kg), while at the 20-30 cm depth the exchangeable K was 86 (mg/ kg) and the mean for TBK was 92 (mg/ kg).

(NB. include summary table of soils data;
Report on most important statistical findings, trends etc….)

4. Results
Crop establishment
Plant counts were taken on 18/06/2013 and for the lupins there were 33.6 plants per metre squared, while for the wheat there were 158.9 plants per metre squared. There was no significant difference in plant population between the plots because of the applied K fertilizer treatment.

Anthesis dry matter, At mid flowering dry matter samples were taken from the lupin and wheat crops and a significant K treatment effect was detected (P = 0.021).

Anthesis dry matter values (t/ ha) for the Lake Bolac trial site^A

K treatment rate	Wheat (t/ ha)	Lupins (t/ ha)
K0	6.95	3.79
K1	7.48	2.84
K2	8.52	3.84
K3	8.24	3.48

^A5% LSD is 0.67.

Crop dry matter nutrient content The dry matter material was analysed for nutrient content and no significant difference was detected for the N content.

Harvest results - Grain yield The effect of the K fertilizer treatment on grain yield was analysed, but no significant difference was detected. The mean yield for the lupins was 3.31 t per hectare and the mean yield for the wheat was 5.73 t per hectare.

Grain quality variables No significant K fertilizer effect was detected on the thousand grain weight. The mean value for the wheat was 41 g/ 1000 grains and the lupins were 29 g/ 200 seeds.
There was no significant K fertilizer effect on the dry matter measured at harvest (maturity).