Recipient Organization
WASHINGTON STATE UNIVERSITY
240 FRENCH ADMINISTRATION BLDG
PULLMAN,WA 99164-0001
Performing Department
Crop & Soil Sciences
Non Technical Summary
Broadleaf weeds have greatly impacted chickpea and lentil production in the Pacific Northwest (PNW). Yield losses due to weeds in chickpeas have been estimated at 23-87% (Bhan and Kukula 1987) and up to 100% for lentils (Makowski, 1995). Additional losses include added cost for harvest aid herbicide applications or swathing, and reduced quality (McKay et al. 2002). Because there are no labeled postemergence broadleaf herbicides for chickpea and only metribuzin in lentil, broadleaf weeds severely limit productivity. Thus, preemergence herbicides must be applied at timings which provide effective weed control long enough to reduce or eliminate the impact of weeds on chickpea or lentil yield. This period is referred to as the critical weed-free period. While the critical weed-free period for chickpeas has been studied, the results have been quite variable (see Table). Moreover, most of the work defining the critical weed-free period in chickpeas has been done in Asia and none has been done in North America. There has been much less research on the critical weed-free period for lentils than for chickpeas. Thus, there is a need to determine the critical weed-free period for both chickpeas and lentils in the Pacific Northwest. Knowing the critical weed-free period for chickpeas and lentil is of little value without effective weed control measures. Since tillage and hand weeding options in chickpeas and lentil are limited or not cost effective, there is a need to evaluate herbicides for use in chickpeas and lentil. Most importantly, there is a need to evaluate pre- and postemergence broadleaf herbicides for use in chickpeas and lentil. Once identified, herbicides could be entered into the Interregional 4 project which assists in labeling pesticides for use in minor crops. Previous research to evaluate herbicides in chickpeas and lentil has identified a few potential products. These products need further evaluation for rate, timing, and duration of weed control.
Animal Health Component
60%
Research Effort Categories
Basic
10%
Applied
60%
Developmental
30%
Goals / Objectives
Objectives: 1. Determine critical weed-free period for broadleaf weeds in chickpea and lentil. 2. Evaluate herbicides and timing of application for weed control in chickpea and lentil Yield reductions in chickpeas due to competition from weeds have been reported to be 23 to 87% (Bhan and Kukula 1987). Mohammadi et al. (2005) estimated 10% reduction in chickpea seed yield for every additional 26 gm m-2 of weed dry weight. Yield loss varies due to intensity of infestations and varying species of weeds between locations (Bhan and Kukula 1987). Yield reduction in lentils due to weeds has not been as extensively tested. Yield loss estimates from weeds in lentils has been estimated to be 100% (Makowski 1995) Generally, weeds emerging before or at crop emergence have a greater competitive advantage than those emerging later (Bosnic and Swanton 1997; Dieleman et al. 1995). Crop emergence patterns, short plant height, or architecture of chickpeas and lentil allow weeds to compete effectively. Early establishing weeds, particularly those emerging before the crop, have a competitive advantage over the later emerging crops and will severely reduce crop yields if not controlled (Kropff et al. 1992). Late emerging weeds compete with the crop as seeds develop and directly reduce seed size or quality. The critical weed free period is defined as the period of crop growth during which the crop must be kept weed free to prevent yield loss due to weed interference (Van Acker et al. 1993). Mohammadi et al. (2005) indicated emergence of chickpea occurred at 5 and 8 days after planting at two locations in Iran. Weed removal studies by these researchers indicated that the critical weed free period was from 0 to 49 days after emergence. A study in Tunisia estimated the critical weed free period for chickpeas at 10 weeks after emergence for a location with a low to medium severity of weed infestation and 4 weeks for a separate location where the infestation was described as severe (Knott and Halila 1986). The critical weed-free period for lentils has not been extensively studied. Nevertheless, the critical weed-free period has been reported to range from about 5 to 14 weeks after emergence (Singh et al. 1996). In reality, the critical weed free period is an estimate and will vary with environment.
Project Methods
Two varieties of chickpea will be planted at each location: Sierra and Dylan. These varieties were selected because they have simple and compound leaf types, respectively. Seeding rate will be 175,000 seed per acre. Additionally, Brewer and Pardina lentils will be seeded. suration of weed-free and duration of weed competition. Treatments which address the weed-free component will include season long weed-free; and weed-free periods of 2, 4, 6, 8, 10, and 14 weeks following planting. Weeds will be removed weekly from the plots by hand for the duration of the weed-free period after which any weed that emerges will be allowed to grow until crop maturity. Treatments will include a nontreated control; and periods of weed competition duration of 2, 4, 6, 8, 10, and 14 weeks following planting. Weeds will be removed by hand for after the appropriate duration of weed competition and then hand weeded as needed weekly until crop maturity. Weeds will be separated by species and weighed to determine species and total weed biomass. Chickpea and lentil height will be measured at 2, 3, 4, 5, 6, 8, 10, and 14 weeks after planting as well as at harvest. Developmental stage of chickpea and lentil will also be noted at these intervals. Chickpea and lentil will be harvested dried and weighed before removing and weighing chickpea or lentil seed. Seed yield from the various treatments will be plotted as a percentage of the weed-free treatment. Most likely, the Gompertz equation will be used to describe the effect of increasing lengths of weed-free period on chickpea yield while a logistical equation will be used to describe the effect of increasing duration of weed infestation (Knezevic et al. 2002). However, other linear and nonlinear statistical methods may be applied depending upon results of the research. A comparison will be made between simple and compound leaf varieties to determine if critical weed-free period response differs. Objective 2. Trials will be conducted at two locations in each of two years. Herbicide treatments will be preplant and preemergence imazethapyr, sulfentrazone, metribuzin, and linuron herbicides for mayweed chamomile control. Treatments will be arranged in a randomized complete block design with 4 replications. Seeding rate will be 175,000 and 450,000 seed per acre for chickpea and lentils, respectively. Seedling will be done with a drill with 7 in. row spacing. The experiment will be laid out as a random complete block design with four replications. Herbicide application timings will be 4 and 2 weeks prior to targeted planting date; at planting; and 1 and 2 weeks after planting. Chickpea and lentil stand counts will be taken three weeks after planting by counting the number of plants along two 1-m sections of row. Weed counts will be taken 2,4 6, 10, and 14 weeks after planting. Weed biomass will be measured in two 0.25-m2 quadrats per plot just prior to chickpea or lentil harvest.