Sunn hemp, Crotalaria juncea L., is a warm-season legume that is planted before or after a vegetable cash crop to add nutrients and organic matter to the soil ( Cherr et al., 2006 , 2007 ; Mansoer et al., 1997 ; Wang et al., 2005 ). This cover
Robert L. Meagher Jr., Rodney N. Nagoshi, James T. Brown, Shelby J. Fleischer, John K. Westbrook and Carlene A. Chase
Alyssa H. Cho, Carlene A. Chase, Danielle D. Treadwell, Rosalie L. Koenig, John Bradley Morris and Jose Pablo Morales-Payan
action ( Marcias et al., 2007 ; Putnam and Tang, 1986 ). Sunn hemp has rapid stand establishment and shoot biomass accumulation and thus is a suitable cover crop for weed suppression. A leguminous cover crop, sunn hemp obtains nitrogen through biological
Michael J. Adler and Carlene A. Chase
). Recently, there has been increased interest in using leguminous cover crops in sustainable and organic cropping systems in Florida ( Abdul-Baki et al., 2005 ; Collins, 2004 ; Scholberg et al., 2006 ). Species such as cowpea, sunn hemp, and velvetbean can
Muhammad Mansoor Javaid, Manish Bhan, Jodie V. Johnson, Bala Rathinasabapathi and Carlene A. Chase
Sunn hemp, a multipurpose species used for fiber, fodder, and biomass ( Cook and White, 1996 ), is widely grown in tropical and subtropical agricultural systems for its usefulness as a cover crop and green manure. A cover crop of sunn hemp can
Sunn-hemp, Crotalaria juncea L. cv. Tropic Sun was developed in Hawaii in 1982 and recently introduced to the island of Guam by USDA Soil Conservation Service as a potential green manure crop. An evaluation of various legumes at three different soil regimes revealed that sunn-hemp produced greater biomass than other plants. In the study of the effects of sunn-hemp in subsequent vegetable production, slightly greater canopy was observed for potato, Solanum tuberosum cv. Kennebec, with green manuring with sunn-hemp than without. Yield of head cabbage, Brassica oleracea var. capita cv. KK Cross, was higher with green manuring (1085.5g/head) than without (725.4g/plant). Competition between indigenous rhizobia and introduced inoculant seems to exist at some locations. Major constraints in using sunn-hemp as green manure on the island are its limited seed sources and requirements of additional labor. Education and promotion of using this legume in a long term soil-improving system is needed.
A.A. Abdul-Baki, H.H. Bryan, G.M. Zinati, W. Klassen, M. Codallo and N. Heckert
Prolific flowering is essential for economic seed production in sunn hemp (Crotalaria juncea L.). Since flowers appear as racimes on the distal portions of secondary branches and since the branching is restricted by a strong apical dominance, lifting the apical dominance by cutting the tops of plants should induce more branches and more flowers per plant. We evaluated this concept in a field experiment conducted in 1999 at the Tropical Research and Education Center, Univ. of Florida, Homestead, by cutting main stems of 100-day-old plants in a dense stand (113,000 plants/ha) at 30, 60, and 90 cm above the soil surface. Cutting at all heights induced more branching and flowering than the control. The highest positive response was in plants in which the main stem was cut at 90 cm above soil surface.
Laura Avila, Johannes Scholberg, Nancy Roe and Corey Cherr
Increased dependency of conventional agriculture on inorganic fertilizers and fossil fuels may hamper long-term sustainability of agricultural production. Sunn hemp (Crotalaria juncea) was tested during summer in a Community Supported Agriculture vegetable crop operation located in Southeast Florida, from 2003 to 2005. Farm system components included sunn hemp (SH) vs. a conventional fallow during summer, tomato (Lycopersicon esculentus) and pepper (Capsicum annum) during winter and spring sweet corn (Zea mays). Tomato and pepper were fertilized with 0, 67, 133, 200 kg N/ha (2003) vs. 0,100, 200 kg N/ha (2004/05). Sweet corn received 133 or 200 kg N ha (2003) vs. 100 kg N/ha (2004/05). Average SH biomass was 3.7 Mg/ha. In 2003 tomato yields following SH without supplemental N were similar to fallow, with 200 kg N/ha. By the third year, tomato and pepper yields in SH plots were 25% and 26% higher, respectively. Conventional pepper amended with 200 kg N/ha had only 8% higher yields than treatments amended with 100 kg N ha and CC. Overall, sweet corn had low yields, but yields increased if the preceding tomato/pepper crop received higher N rates. In 2003, sweet corn fertilized with 200 kg N/ha following a SH-fall vegetable crop produced 17% higher marketable yields compared to the fallow treatment. During 2004 and 2005, sweet corn within the SH-non-fertilized tomato system produced 29% higher yields compared to a similar conventional system. Results show that, in this rotation, both fall vegetable crops and sweet corn yield benefit from residual N fertilizer. Mineralization of SH may thus not only benefit the immediately following crop, but its effects can be seen later during the year.
Alyssa H. Cho, Alan W. Hodges and Carlene A. Chase
( Klassen et al., 2006 ). Sunn hemp produced the most groundcover and, therefore, the greatest weed suppression in comparison with other cover crops, suppressing 50% to 82% of weeds ( Sangakkara et al., 2006 ). The study also showed that a cash crop of mung
Anthony M. Ortiz, Brent S. Sipes, Susan C. Miyasaka and Alton S. Arakaki
[black hollyhock (cv. Nigra); canola (cvs. Dwarf Essex and Sunrise Canola); cabbage (cv. Capitata); French marigold (cvs. French Brocade and Pesche’s Gold), sorghum–sudangrass (cvs. Piper and Sordan 79); sunn hemp; and yellow mustard (cv. Ida Gold)] were
Jialin Yu, Nathan S. Boyd and Zhengfei Guan
-parasitic nematode populations ( Wang et al., 2002 , 2006 , 2007 ), and many of these, particularly legumes, increases soil fertility for the subsequent crops ( Wang et al., 2006 ). Sunn hemp ( C. juncea L.) is a legume cover crop and is thought to have important