S-metolachlor and rainfall effects on sweetpotato (Ipomoea batatas L. [Lam]) growth and developmentScientia Horticulturae


Issah A. Abukari, Mark W. Shankle, K. Raja Reddy


Scientia Horticulturae 185 (2015) 98–104

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Scientia Horticulturae journa l h om epa ge: www.elsev ier .com/ locate /sc ihor t i

S-meto ato (Ipomo m

Issah A. A a Cassava and S cultura

Tamale, Ghana b Pontotoc Ridg ter, 83 c Department o sissipp a r t i c l e i n f o

Article history:

Received 3 March 2014

Received in revised form 16 December

Accepted 21 Ja


Herbicide inju

Storage roots


Yield reductio a b s t r a c t

The herbicide S-metolachlor is used to control or suppress annual grasses, nutsedges and several broadleaf weeds in sweetpotato. However, a decline in storage root quality is suspected when an excessive rainfall occurs within 24 h after application. A sunlit, controlled environment experiment was conducted to inves1. Introdu

Sweetpo tant food c developing sweetpotat with China 2014). In th metric tons

Abbreviati ∗ Correspon

E-mail add http://dx.doi.o 0304-4238/© 2014 nuary 2015 ry n tigate sweetpotato response to five levels of S-metolachlor (0.00, 0.86, 1.72, 2.58 and 3.44 kg ha−1), and two levels of simulated rainfall (0 and 38 mm at 51 mm h−1) immediately after application. Sweetpotato slips were transplanted into white polyvinyl chloride pots filled with sandy loam soil. S-metolachlor treatments were applied to slips and a simulated rainfall treatment delivered immediately after transplanting and herbicide treatment. All pots were transferred to sunlit growth chambers that were maintained at 30/22 ◦C, day/night temperatures and ambient carbon dioxide concentration (400 L L−1) for 60 days. An evapotranspiration-based irrigation system was used to supply water and nutrients. Plant biomass components and quality of storage roots were recorded 60 days after transplanting. There was no difference between rainfall treatments across S-metolachlor rates for vine lengths, leaf numbers and leaf area. These parameters, however, declined linearly and significantly with increase in S-metolachlor concentration.

Total storage root weight declined linearly with increased S-metolachlor concentration; the decline was steeper with simulated rainfall. Yield of marketable storage roots declined by 18 and 31% in the absence of rainfall and 55 and 79% in the presence of rainfall with S-metolachlor at minimum (0.86 kg ha−1) and maximum (1.43 kg ha−1) recommended label rates, respectively, used to control weeds. Yield reduction was directly proportional to the rate of S-metolachlor applied in the absence or presence of rainfall; 77 and 123 g fresh weight kg−1 ha−1 S-metolachlor for no-rainfall and rainfall treatment, respectively. These results can be used to improve management decisions to optimize yield under field conditions as well as to mitigate risk of injury that could be associated with the use of S-metolachlor in sweetpotato production systems. © 2015 Elsevier B.V. All rights reserved. ction tato [Ipomoea batatas (L.) Lam.] is the sixth most imporrop in the world and fifth most important crop in countries (International Potato Center, 2010). World o production was 103 million metric tons in 2013 accounting for 71% (Food and Agriculture Organisation, e same year, the United States produced 1.3 million from 45,800 ha with a crop value of $552 million ons: DAT, days after transplanting; SR, storage root. ding author. Tel.: +1 662 325 9463; fax: +1 662 325 9461. ress: krreddy@pss.msstate.edu (K.R. Reddy). (USDA-NASS, 2014a). Mississippi ranked second in acreage among

US sweetpotato producing states with 7,891 ha yielding a crop value of $57.2 million, behind North Carolina with 21,400 ha (USDA-NASS, 2014b). In the United States, storage roots are the primary economic product derived from sweetpotato production systems for human consumption, although other plant components are used in other countries for various purposes.

Weeds are a major challenge to sweetpotato production, with hophornbeam copperleaf (Acalypha ostryifolia Riddell), pigweed (Amaranthus spp.), yellow nutsedge (Cyperus esculentus L.), and purple nutsedge (Cyperus rotundus L.) being problematic in the southern US (Kelly et al., 2006). Moody and Ezumah (1974) reported yield losses of 22, 78 and 91% due to uncontrolled weed growth in Hawaii, West Indies and Nigeria, respectively. In other studies, rg/10.1016/j.scienta.2015.01.018 2015 Elsevier B.V. All rights reserved.lachlor and rainfall effects on sweetpot ea batatas L. [Lam]) growth and develop bukaria, Mark W. Shankleb, K. Raja Reddyc,∗ weetpotato Research Unit, Council for Scientific and Industrial Research-Savanna Agri e-Flatwoods Branch Experiment Station, North Mississippi Research and Extension Cen f Plant and Soil Sciences, Mississippi State University, 117 Dorman Hall, Box 9555, Misent l Research Institute, P.O. Box 52, Nyankpala, 20, Hwy 15 South, Pontotoc, MS 38863, USA i State, MS 39762, USA

I.A. Abukari et al. / Scientia Horticulturae 185 (2015) 98–104 99 weed interference has caused yield reductions ranging from 14 to almost 70% in various sweetpotato cultivars (LaBonte et al., 1999;

Harrison and Jackson, 2011).

The critical weed-free period for Beauregard sweetpotato is 2–6 weeks weed contr most comm hand weed ment progr sweetpotat is restricted growth hab has become

The herb agement sy wide spect addition, it press yellow 2006). S-m solubility o carbon-wat and 0.11 m matter (OM metolachlo

OM (Sensem soils espec and as a re the first irr soybean [Gl garis L.) inj with pre-em of dimethe et al., 2009 shoots, but the site of

It is primar inhibitor as such as fatt susceptible in sweetpo plant (PRE) slips.

Despite ling many hesitant to misshaped bicide und 2012). Thou effects of S growth, yie effects have a controlled (SPAR) plan cisely meas allows for t factors that et al. (1981 applied at stunting fo 2.2 and 3.4 to the untre metolachlo canners, an limited info transplant o as affected