Soil fumigation and runner plant production: A synthesis of four years trials of strawberry nursery field

Abstract

Strawberry (Fragaria xananassa L.) runner plant production during a 4-year period was compared on nursery soils treated with methyl bromide (MB) and chloropicrin (CP) mixtures (MB:CP) and three alternative soil treatments: CP, mixtures of 1,3-dichloropropene (Telone®) and CP (DP:CP), and no fumigation (NF). The effect of soil treatment on runner plant production for a single nursery propagation cycle was determined in all 4 years. In 2 years, runner production in a final propagation cycle was also determined as a function of soil treatment in previous cycles. A single propagation cycle in NF soil decreased runner production relative to all other treatments. Treatments with CP at rates of 140 to 191 kg · ha-1 generally decreased runner production significantly (P ≤ 0.05) in comparison with treatment with MB:CP; use of CP at rates ≥303 kg · ha-1 resulted in statistically equivalent runner production. In one trial, use of two DP:CP formulations (516 kg · ha-1 of a 7:3 DP:CP mixture, and 448 kg · ha-1 of a 3:7 DP:CP mixture) significantly reduced and did not affect runner production, respectively, relative to the use of MB:CP. Use of MB:CP in the previous propagation cycle also increased runner productivity in comparison with NF. Runner productivity of planting stock produced with 314 kg · ha-1 of CP did not differ statistically from that of stock produced with MB:CP, but productivity of planting stock on soil treated with 157 kg · ha-1 of CP was intermediate between that on NF and MB:CP-treated soil. Planting stock grown on nontreated soil in two previous propagation cycles produced 25% fewer runner plants than did similar stock grown on MB:CP-treated soil. Productivity of planting stock produced with CP at rates of 280 to 314 kg · ha-1 in two previous propagation cycles did not differ statistically from that of stock produced with MB:CP. Results of meta-analyses indicated that fumigation with MB:CP was more effective in increasing runner production than was CP or NF, regardless of the propagation cycle or rate of application. For mixtures of 1,3-dichloropropene and CP, nursery productivity was maximized by using at least 280 kg · ha-1 of CP.