Critical Period for Weed Control in Grafted and Nongrafted Fresh Market Tomato

Abstract

Field experiments were conducted to determine the critical period for weed control (CPWC) in nongrafted ‘Amelia’ and Amelia grafted onto ‘Maxifort’ tomato rootstock grown in plasticulture. The establishment treatments (EST) consisted of two seedlings each of common purslane, large crabgrass, and yellow nutsedge transplanted at 1, 2, 3, 4, 5, 6, and 12 wk after tomato transplanting (WAT) and remained until tomato harvest to simulate weeds emerging at different times. The removal treatments (REM) consisted of the same weeds transplanted on the day of tomato transplanting and removed at 2, 3, 4, 5, 6, 8, and 12 WAT to simulate weeds controlled at different times. The beginning and end of the CPWC, based on a 5% yield loss of marketable tomato, was determined by fitting log-logistic and Gompertz models to the relative yield data representing REM and EST, respectively. In both grafted and nongrafted tomato, plant aboveground dry biomass increased as establishment of weeds was delayed and tomato plant biomass decreased when removal of weeds was delayed. For a given time of weed removal and establishment, grafted tomato plants produced higher biomass than nongrafted. The delay in establishment and removal of weeds resulted in weed biomass decrease and increase of the same magnitude, respectively, regardless of transplant type. The predicted CPWC was from 2.2 to 4.5 WAT in grafted tomato and from 3.3 to 5.8 WAT in nongrafted tomato. The length (2.3 or 2.5 wk) of the CPWC in fresh market tomato was not affected by grafting; however, the CPWC management began and ended 1 wk earlier in grafted tomato than in nongrafted tomato.

Critical Period for Weed Control in Grafted and Nongrafted Watermelon Grown in Plasticulture

“…EST and REM studies were conducted in separate but adjacent fields similar to other CPWC study designs (Chaudhari et al 2016). The two studies were designed with the intention to overlay the data onto one graph to determine the CPWC, the period when weeds must be controlled to reach a yield threshold below the acceptable yield loss (AYL).…”

“…If grafted watermelon exhibit greater early-season growth, more rapid canopy closure, or increased vigor, it would be expected that grafted plants have a shorter CPWC due to an enhanced weed competitive ability of the grafted plants. The duration of the CPWC was similar for grafted (2.3 wk) and nongrafted (2.5 wk) tomato ( Solanum lycopersicum L.); however, the CPWC began and ended 1 wk earlier in the grafted treatment (Chaudhari et al 2016). Thus, grafting did not eliminate or reduce the need for timely weed control in tomatoes; instead, weed control must be enacted 1 wk earlier in grafted plants relative to nongrafted plants.…”

“…Grafting onto vigorous rootstocks may affect the crop–weed competitive relationship. Grafted plants reportedly grow at different rates than nongrafted plants (Lee 1994), which may affect the duration of the critical period for weed control (CPWC) or cause the CPWC to occur at different times within the season (Chaudhari et al 2016). If left uncontrolled, weeds can cause substantial reductions in watermelon yield.…”

Cultural weed management practices shorten the critical weed-free period for soybean grown in the Northern Great Plains

“…When modelling biological systems, it is desireable that each model parameter describe a biological function without interference from another parameter (Ratkowsky 1990). Previous CPWC studies have had difficulties identifying the biological significance of all modelled parameters and many authors have simply referred to those as constants that describe a mathematical function (for example see Chaudhari et al 2016, Hall et al 1992, Van Acker et al 1993. In the CTWR and CWFP models, the Datasets collected for the purpose of modelling the CPWC are unique to the conditions where they were collected, and from a statistical perspective, models that best fit the data should be chosen (Ratkowsky 1990).…”

“…The CWFP has been defined for soybean (Halford et al 2001, Van Acker et al 1993) and other crops (Chaudhari et al 2016, Fedoruk et al 2011, Hall et al 1992.…”