Effects of growing media and nutrition on tuber russeting, storage, and production inSandersonia aurantiaca

Abstract

The effects of three planting media (50:50 peat:pumice, Pinus radiata bark, and soil) at two nutrient rates (1.0 and 4.0 kg/m 3 Nutricote) were assessed on sandersonia (Sandersonia aurantiaca (Hook.)) tuber production, the incidence of tuber russeting, and subsequent performance of tubers. Tuber weights were greater at the higher nutrient rate. Lighter tubers were produced in the bark medium than in the peat:pumice or soil. Tuber russeting was less, and commercially acceptable, at the low nutrient rate in all media. At the high nutrient rate russeting was greater in tubers grown in peat:pumice and soil compared to those grown in bark. At the high nutrient rate tissue concentrations of K, N, S, and P were greater. Tubers grown in bark had lower concentrations of N and S compared to tubers grown in soil and peat. At the high rate of nutrition tuber sprouting in the subsequent season was less in the tubers grown in soil and peat:pumice compared to the bark-grown tubers. Stem length, stem weight, flower number, and vase life from tubers produced in bark at the high nutrient rate were similar to those produced in the soil and peatpumice media at the low nutrient rate. There was no improvement in production indices for the tubers grown in soil or peat:pumice at the high nutrient rate. These findings show that if grown in peat:pumice or soil, sandersonia tubers should be produced at low nutrient levels to reduce the incidence of tuber russeting and to improve subsequent forcing. If grown in bark media, higher nutrient rates can be used to maintain forcing quality without causing high levels of russeting.

Effects of soilless media, nutrition, and pH on tuber russeting inSandersonia aurantiaca

“…Tuber weight increased with N rate in the bark medium, but in the peat/pumice medium maximum tuber weight occurred at the middle N rate (100 g/m 2 ). The high N rate resulted in higher tuber N concentrations (3.92-4.22% dry weight) than reported previously (Clark 1997;Clark & Burge 1999a, 2000. In these previous studies N rates were 5-227.2 g N/m 2 and maximum tuber weight occurred at tuber N concentrations of c. 2.0-2.5%.…”

“…The russeting score increased in the peat/ pumice medium up to 100 g N/m 2 and in the bark medium to 500 g N/m 2 . Clark & Burge (2000) also found that russeting scores were greater at increased nutrient rates and in peat/pumice compared to bark but the russeting scores were greater at the higher nutrient levels for both media. The tuber russeting scale used gives a score of 3.0 as minor russeting and is probably acceptable for local sales.…”

“…There are differing relationships between russeting scores and N rate for the two media. Clark & Burge (2000) found a relationship between tuber N (R 2 = 0.862) and K (R 2 = 0.752) concentration and tuber russeting score. Our earlier study only tested nutrient rates up to 68.2 g N/m 2 and 43.2 g K/m 2 .…”

“…The number of secondary tubers and the degree of russeting of each tuber was scored. Russeting scores were on a scale of 1-7 (Table 1) as per Clark & Burge (2000). A random sample of five tubers was collected from each of three replicates within each treatment for analysis of nutrient content by Celentis Analytical.…”

“…Tuber russeting in sandersonia is described in our initial study (Clark & Burge 2000) as ranging from very minor red/brown surface cracking, through to a moderate degree of cracking with tubers having some yellow colouring and light callus development, to major cracking and heavy callus over the majority of the tuber. We found that russeting was greater in soil and peat/pumice media than in bark-based media and that it increased with nutrition level.…”