Changes in the Concentration of Leaf Nitrogen over the Season Affect the Diagnosis of Deficiency or Sufficiency in Strawberries in the Subtropics

Abstract

Optimum leaf nitrogen (N) concentrations have been identified for strawberry (Fragaria ×ananassa Duch.) in temperate and Mediterranean areas, but whether these values are appropriate for the subtropics is unclear. Two experiments were conducted for 2 years to determine if the seasonal changes in the concentration of leaf N affect the diagnosis of deficiency or sufficiency of strawberry plants in Queensland, Australia. In 2014, ‘Festival’, ‘Fortuna’, and ‘Winter Dawn’ were planted in early April and grown with and without N for the entire season. Then, ‘Festival’ was planted the following year in mid- or late April and, again, was grown with and without N. Yield was slightly lower with N in 2014, but higher with it the following year, particularly in the early planting. The concentration of total N in young, fully expanded leaves decreased from 3.0% to 2.0% as leaf, crown, and root dry weight increased, while the concentration of nitrate-N (NO3-N) decreased from 1200–3200 to 50–500 mg/kg. These changes in leaf N were large enough to affect the diagnosis of N deficiency or sufficiency. The concentration of leaf N was less variable than the concentration of leaf NO3-N and, therefore, better for estimating the nutrient status of strawberry plants in the subtropics.

Temperature Has a Greater Effect on Fruit Growth than Defoliation or Fruit Thinning in Strawberries in the Subtropics

“…The plants were irrigated through drip-tape placed under the plastic when the soil water potential in the root-zone decreased below −10 kPa [22]. The plants were fertilized through the irrigation and received 117 kg N/ha, 24 kg P/ha and 165 kg K/ha and other nutrients as described previously [23]. The main disease affecting the crop was grey mold incited by Botrytis cinerea, with the plants receiving weekly applications of multi-site fungicides such as captan and thiram, and applications of site-specific fungicides such as iprodione, fenhexamid, cyprodinil + fludioxonil, and penthiopyrad during wet weather [22].…”

Higher Temperatures Decrease Fruit Size in Strawberry Growing in the Subtropics

“…This layout provided 77 rows with 666 plants/row for each ha, giving a density of 51,282 plants/ha. The plants were irrigated through driptape placed under the plastic when the soil water potential in the root-zone decreased below −10 kPa [41,42]. Nitrogen and other nutrients were applied by fertigation [42].…”

No Evidence of Excessive Leaf Production by Strawberries Grown in the Subtropics

“…This lay-out provided 77 rows with 666 plants/row for each ha, giving a density of 51,282 plants/ha. The plants were irrigated through drip-tape placed under the plastic when the soil water potential in the root-zone decreased below -10 kPa [37]. The plants were fertilized through the irrigation and received 117 kg N/ha, 24 kg P/ha and 165 kg K/ha and other nutrients as described previously [37].…”

“…The plants were irrigated through drip-tape placed under the plastic when the soil water potential in the root-zone decreased below -10 kPa [37]. The plants were fertilized through the irrigation and received 117 kg N/ha, 24 kg P/ha and 165 kg K/ha and other nutrients as described previously [37]. The main disease affecting the crop was grey mold incited by Botrytis cinerea, with the plants receiving weekly applications of multi-site fungicides such as captan and thiram, and applications of site-specific fungicides such as iprodione, fenhexamid, cyprodinil + fludioxonil and penthiopyrad during wet weather [3].…”