Special Research Report #532 Production Technology Using Soil Moisture Sensors for Poinsettia Height Control

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Specil Reserch Report #532 Production Technology Using Soil Moisture Sensors for Poinsetti Height Control Alem Peter 1, Pul Thoms 1, Mrc vn Iersel 1, nd Stephnie

04469 BACKGROUND In generl, plnt height control is criticl issue with floriculturl crops. With potted poinsetti production, it is very importnt.

The most common method to control plnt height is through the ppliction of plnt growth retrdnts (PGRs).

1 Specil Reserch Report #532 Production Technology Using Soil Moisture Sensors for Poinsetti Height Control Alem Peter 1, Pul Thoms 1, Mrc vn Iersel 1, nd Stephnie Burnett 2 1 Deprtment of Horticulture, University of Georgi, Athens, GA nd 2 Deprtment of Plnt, Soil, nd Environmentl Sciences, University of Mine, Orono, ME BACKGROUND In generl, plnt height control is criticl issue with floriculturl crops. With potted poinsetti production, it is very importnt. Sle contrcts for poinsettis commonly include plnt height specifictions nd growers must produce plnts tht fll within specified height rnge. The most common method to control plnt height is through the ppliction of plnt growth retrdnts (PGRs). PGRs cn be pplied s spry or drench, but their efficcy is not lwys predictble. Some PGR pplictions to poinsetti cn result in excessive stunting nd decresed brct size; thus, reducing plnt qulity. Figure 1. Overview of the study ner the beginning (top) nd end of the study. 1

3 The study included four tretments: control without imposed height controls, drench tretment (0.25 ppm Bonzi), spry tretment (1000 ppm B-Nine nd Cycocel), nd wter deficit tretment. In the wter deficit tretment, substrte wter content ws llowed to drop to 20% nd then mintined t 20% until plnt height ws within the rnge specified by the growth-trcking curve. At tht time, substrte wter content ws incresed bck to 40%. RESULTS Plnt height exceeded the upper height limit soon 80 fter pinching (Fig. 3). Thus, PGR sprys nd drenches were pplied 60 twice, t 12 nd 33 dys fter pinching. Elongtion ws slow fter b the second PGR 40 ppliction nd the finl height of plnts treted with PGRs ws slightly below the lower 20 cceptble limit of 16 inches. Substrte wter content ws pplied 0 twice, the first ppliction Control Drench Spry Wter deficit ws 21 till 28 dys fter pinching nd the second ppliction ws from 54 till 57 dys fter pinching. This resulted in finl plnt height Figure 4. The effect of different height control methods on the finl plnt height of poinsettis Cv. Clssic Red. of 17.8 inches. This wter deficit tretment ws the only tretment with plnt height within the finl trget height of 16 18inches (Fig. 3, 5). In ddition to stunting the plnts, PGR sprys reduced the size of the brcts by 44% compred to untreted plnts (Fig. 4). The PGR drench nd controlled wter deficit did not hve ny negtive impct on brct size. None of the tretments impcted the color of the brcts. CONCLUSIONS Brct size (cm 2 ) Soil moisture sensor-controlled irrigtion systems cn be used to pply controlled wter deficit to poinsettis. This is n effective wy to regulte stem elongtion nd to control the mrketble plnt height. We did not observe ny negtive side effects of the wter 3

deficit on the plnts. PGR tretments reduced height more thn desired. In ddition, the PGR spry reduced brct size nd, thus, plnt qulity. Figure 5. Representtive plnts poinsettis Cv.

4 deficit on the plnts. PGR tretments reduced height more thn desired. In ddition, the PGR spry reduced brct size nd, thus, plnt qulity. Figure 5. Representtive plnts poinsettis Cv. Clssic Red from the vrious tretments. From left to right: control plnts without ny height control, plnts drenched with PGRs, plnts spryed with PGRs, nd plnts exposed to controlled wter deficit. Only plnts exposed to controlled wter deficits hd finl height within the trget rnge. INDUSTRY IMPACT The use of soil moisture sensor-controlled irrigtion llows growers to pply specific wter deficit to their crop. This cn be used to mnipulte the elongtion of the plnts. This occurs through the ppliction of wter deficit when plnts re tller thn desired. It slows their growth, but it resumes fter norml irrigtion is resumed. This provides growers with new, non-chemicl method to control plnt height. With the incresing consumer preference for reduced chemicl use, plnts tht hve not been treted with PGRs might be preferred by mny consumers. This reserch ws funded, in prt, by USDA-NIFA-SCRI Awrd no , August Copyright Americn Florl Endowment All Rights Reserved For dditionl informtion contct The informtion contined in this report my not be reproduced without the written consent of the Americn Florl Endowment. For more informtion contct Debi Aker t (703)

5 Americn Florl Endowment Phone: Fx:

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