printed by ORGANIC NO-TILL VEGETABLE PRODUCTION SYSTEM: WEED MANAGEMENT WITH COVER CROPS Gurudev Mayalagu* 1, Rao Mentreddy 1, Joseph Kloepper 2 1 Department of Natural Resources and Environmental Sciences, Alabama A & M University, Normal, Alabama Department of Plant Pathology, Auburn University Organic farming is a recent trend to produce food free from hazardous contaminants. It involves developing biological diversity in the field disrupting pest organisms, intentional maintenance and replenishing nutrients. Weed management is a global challenge in organic farming. Under no-till conditions cover crops are incredible tool to harvest multi-benefits of weed suppression, reduce soil- erosion, break pest cycles, conserve moisture, protect beneficial organisms, and amend soil. There is limited research on cover crop- weed interaction. Field experiments were conducted at Hazelgreen, AL to study five winter cover crops, Austrian winter peas (AWP), canola (CAN), crimson clover (CC), hairy vetch (HV), and rye (R) for their relative efficiency on weed control, biomass production, canopy cover, soil fertility and summer cash crops yield, compared against control- fallow (F). Percent canopy cover and cover crop biomass were determined. Plant stand and canopy generally increased in all plots except for canola. Weed suppression was 100% in canola and rye, and gradually increased in CC and HV with biomass. The weed biomass in R, CC, AWP, HV and CAN was respectively 21, 7, 2, 1.5 and 1.3 times lower than in control. In addition to weed suppression, soil fertility effects were observed. Soil analysis showed a consistent decrease of P across all the treatments through the winter but an increase of 43 kg ha -1 (CC) and 13 kg ha-1 towards end of summer. The fresh tomato and pepper yield followed the same trend of highest (50 Mg ha -1 ) in AWP followed by CC similar to F, compared to CAN, HV and R ranging from 39 to 21 Mg ha -1. Rye was efficient weed suppressor in winter but had considerably affected the yield of cash crops in summer. Cover crops showed variation in weed suppression, through light interception by canopy cover, allelopathic effect, biomass as mulch, and also kept nutrients from leaching. Thus, choice and establishment of cover crops are very critical to manage weeds, reduce leaching, and will serve as an eco-friendly alternative to conventional farming. Biomass: Among the winter cover crops CC produced highest quantity of biomass and rye was the most superior weed suppressor. Though CAN produced higher biomass than HV it was least in weed suppression. Higher the biomass higher the weed suppressed holds well with R, CC and AWP (Fig.1). Fallow biomass is of weeds affecting C:N & OM%. Carbon & Nitrogen: Plant analysis showed, cereal rye had the highest C:N ratio (55.5) and AWP (13.7) the lowest (Fig.2). CC and AWP contributed more than 50 kg N ha -1 over F (61 kg), while R had the least of 38 kg N ha -1. The CC and AWP plots showed higher percentage of OM in top 3-inches of soil surface and lower concentration of nitrate-N. Major nutrients: The highest NO3-N of 4.4 ppm (F) and lowest of 3.4 ppm (AWP) were recorded. No treatments did not showed significant differences in K, Mg and CEC levels, whereas P level reduced about 6 kg ha -1 consistently in all treatments including F Control (Fig.5). In CAN plot no change in Ca was noticed while it increased in the order of F, CC, HV, AWP and R. CEC had a slight decrease in CAN but rest of the treatments showed no major difference. Towards the end of summer cash crop, a significant increase in P was recorded in CC (43 kg) and R (13 kg) per hectare.(Fig.4) Yield: Yield trends were same with tomato and pepper. Highest yield in CC and AWP was comparable to F. Rye suppressed weeds, but compromised on yield. C:N ratio of cover crops and yield were inversely related. Location: Winfred Thomas Agricultural Research Station, Alabama A & M University, Hazelgreen, Alabama. Winter Cover Crops: [5] a) Hairy vetch (Vicia villosa Roth); b) Crimson clover (Trifolium incarnatum L.); c) Long vine Austrian winter peas (Pisum sativum subsp. arvense); d) Canola (Brassica napus L.); and e) Cereal rye (Secale cereale L.); CONTROL: Fallow. (Pic.1) Cash Crops: Tomato and Pepper (Pic.2) Date Planted: October 2005 Net Plot Area: 25m x 25m SMALL PLOT EXPERIMENT Net Plot Area: 1m x 6m. REPLICATIONS: Four. Soil Amendment: Lime to bring the soil pH to 6.0; Fertilizer: OMRI Approved composted poultry manure; steamed bone meal, and organic calcium. OBSERVATIONS AND MEASUREMENTS Cover Crop Biomass: Above ground biomass of cover crops and weeds were collected separately from an area of 0.25 m2 and dried at 90 degree Celsius for 3 days and weighed. Weed Suppression %: [Weed biomass (F)-Weed biomass (cover crop)] / Weed biomass (F)*100 Yield: In the following summer season, tomato and pepper yields were estimated by marking sub-sample plants and taking weight of marketable fruits by periodical harvest. Soil & Plant Analysis: Soil samples were collected using core sampler at the depth of 7.5 cm for NO 3 -N and OM analysis, and 15 cm for major nutrient analysis. Plant samples were same as the samples used for above ground biomass. Both samples were analyzed at Auburn Soil testing lab, Auburn University by Mehlich-1 method. Statistical Analysis: All data was analyzed using proc GLM procedures of SAS (2003). Means separation was by the DMRT. Akemo, M. C., E. E. Regnier, and M. A. Bennett Weed suppression in spring-sown rye (Secale cereale)–pea (Pisum sativum) cover crop mixes. Weed Technol. 14:545–549. Boydston, R. A. and A. Hang Rapeseed (Brassica napus) green manure crop suppresses weeds in potato (Solanum tuberosum). Weed Technol. 9:669–675. Carrera, L.M, Buyer, J.S., Vinyard, B., Abdul-Baki, A.A., Sikora, L.J. and J.R. Teasdale Effects of cover crops, compost, and manure amendments on soil microbial community structure in tomato production systems. Appl. Soil Eco. 37(3): Creamer, N. G., M. A. Bennett, and B. R. Stinner Evaluation of covercrop mixtures for use in vegetable production systems. HortScience 32: 866–870. Di, H. J., and K. C. Cameron Nitrate leaching in temperate agroecosystems: sources, factors and mitigating strategies. Nutr. Cycl. Agroecosyst. 64:237–256. Sainju, U. M., B. P. Singh, and W. F. Whitehead Long-term effects of tillage, cover crops, and nitrogen fertilization on organic carbon and nitrogen concentrations in sandy loam soils in Georgia, USA. Soil Tillage. Res. 63:167–179. Teasdale, J. R. and A. A. Abdul-Baki Comparison of mixtures vs. monocultures of cover crops for fresh-market tomato production withand without herbicides. HortScience. 33:1163– Tu, C., Ristaino. J.B., and Shuijin Hu Soil microbial biomass and activity in organic tomato farming systems: Effects of organic inputs and straw mulching Soil Bio. Biochem.38(2): C:N ratio of cover crops is directly related to the ability of cover crops to suppress weeds. Rye is a good weed suppressor but may compromise on cash crop yield. Cover crops affect the productivity of soil by minimizing nutrient loss, contributing soil carbon and nitrogen,. Objectives: To evaluate five winter cover crops (rye, Austrian winter peas, crimson clover, hairy vetch) for their ability to suppress weeds against fallow control. To compare the dry biomass contribution of five winter cover crops to fallow. To understand the relationship of different winter cover crops to soil fertility and effect on subsequent mid-summer cash crops yield. Hypothesis:  Winter cover crops suppress weeds.  Winter Cover crops contribute to conservation of nutrients.  Cover crops improved productivity of soil ABSTRACT OBJECTIVES AND HYPOTHESIS MATERIALS AND METHODS RESULTS CONCLUSIONS REFERENCES INTRODUCTION Cover crops are incredible tools in organic vegetable production system. Weed management is a great challenge for the growers of high value crops. Irrigation and weed management can be very expensive. In the winter, cover crops can build biomass, act as mulch, conserve moisture and importantly minimize leaching of macro and micro nutrients. Cover crops enhance sustainalblity of agriculture systems (Sainju et al,. 2002), and reduce nitrate leaching (Di and Cameron, 2002). Creamer et al (1997); Teasdale and Abdul-Baki (1998) have studied on weed suppression by cover crop mulch. Hairy vetch affected the microbial community structure.(Carrera et al, 2007). There are few studies (Boydston and Hang, 1995 evaluating cover crop effects on weeds in tilled, direct-seeded vegetable systems. Research information is limited on weed biomass or seed production during the cover cropping period (Akemo et al,. 2000; Brennan and Smith, 2003). Muching with rye-vetch enhanced microbial biomass, activity, potential N availability compared to non mulched soils thus improving C and water availability. (Tu et al, 2006). This study intends to help make right cover crop choices to suit north Alabama. The authors thank Dr. Suresh Kumar for assisting in preparation of this poster, Mr. Lewis Bingham, Mr. Kadirov and Mr. Reid for assistance with field work. Pic.1.Cover crops: cereal rye (foreground), crimson clover (background). Pic.2. Rows of no-till planted peppers, in rye plot aisle showing weeds suppression. ACKNOWLEDGEMENT