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ARS Home » Plains Area » Mandan, North Dakota » Northern Great Plains Research Laboratory » Research » Publications at this Location » Publication #320946

Title: Intercropped watermelon for weed suppression in a low-input organic system

item Franco, Jose
item KING, STEPHEN - Millican Farms, Llc Tx
item MASABANI, JOSEPH - Texas A&M University
item VOLDER, ASTRID - University Of California

Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2018
Publication Date: 5/1/2018
Citation: Franco Jr, J.G., King, S.R., Masabani, J.G., Volder, A. 2018. Intercropped watermelon for weed suppression in a low-input organic system. HortTechnology. 28(2):172-181.

Interpretive Summary: Organic and sustainably-minded vegetable producers have limited effective weed control options at their disposal. Perennial weeds such as nutsedge are especially difficult to control due to their vigorous reproductive ability, C4 photosynthetic efficiency, and widespread distribution. An intercropping system consisting of architecturally complimentary species creates a dense canopy that reduces light availability to weeds and suppresses weed growth, thereby reducing competition with cash crops. The addition of a cash crop that can serve as a smother crop such as watermelon, in particular, introduces a value-added crop that can effectively suppress perennial weeds such as nutsedge while generating income. The incorporation of an integrated multifunctional system such as the one used in this study offers a promising management tool for organic producers for the control of perennial weeds which are known to cause significant yield losses.

Technical Abstract: A multi-layered canopy provided by intercropping species with different growth forms can provide barriers for the germination of weed seeds and can allow for a more efficient utilization of resources that reduce competition to target crops from weeds. Intercropping can thus be an effective cultural control strategy for the management of weeds in organic production systems. Different combinations of peanut, watermelon, okra, cowpea, and pepper planted alone or in various intercropping combinations were investigated in a low-input organic system in Texas. Each species was selected to perform a specific function within the system. Watermelon was selected as a smother crop and significantly reduced total weed biomass when planted in monoculture and in all intercropping combinations in year 1 of the 2-year study. Total weed biomass was reduced by 81, 83, 88 and 92% in treatments containing watermelon on average as compared to pepper, peanut, okra and cowpea grown in monoculture, respectively. Competition with okra reduced watermelon biomass and its ability to perform as an effective smother crop in year 2. Pepper grown in monoculture had significantly higher weed biomass than all other treatments in year 2, with 46% more weed biomass than the next highest weed-yielding treatment. Broadleaf weeds were most effectively suppressed across all intercropping treatments in year 1, but nutsedges were most consistently reduced both years, particularly in monocrops with small leaf area such as pepper. The three and four species intercropping combinations, Wpwo and Wpwoc, had some of the most consistently high leaf area index (LAI) values, while pepper monoculture had significantly low LAI values. There was a significant positive linear relationship between LAI and total aboveground plant biomass 33, 43, and 63 days after last planting (DALP; P < 0.01) and significant negative linear relationship between LAI and total weed biomass 43 DALP (P = 0.01) and 63 DALP (P < 0.01). There was a significant negative linear relationship between total weed biomass and total fruit yield in year 1 (P < 0.01, R2 = 0.44) and nutsedge weed biomass and total fruit yield in year 2 (P = 0.03, R2 = 0.16). These findings suggest that incorporating a multifunctional intercropping system that includes a smother crop or at least an architecturally complex mixture can optimize canopy density to reduce weed pressure from resilient perennial weeds such as nutsedge. This may offer organic producers another management tool for the control of perennial weeds.