Crop Rotation and Soil Amendment Alters Sorghum Grain Quality

Soybean [Glycine max (L.) Merr.] rotation enhances grain sorghum [Sorghum bicolor (L.) Moench] yield, but infl uence on grain quality has not been measured. The objective was to determine the effect of cropping sequence (CS) and soil amendment (SA) on grain yield and quality. Sorghum grain yield and quality, soil NO3–N and water were measured in a rotation study in 2003 and 2004 on a Sharpsburg silty clay loam (fi ne, smectitic, mesic Typic Argiudoll). Cropping sequences were continuous sorghum, and sorghum rotated with non-nodulating and nodulating soybean. Soil amendments consisted of no amendment, manure (17–26 Mg dry matter ha−1 yr−1), and N (84 kg ha−1 yr−1). CS × SA interaction effects were found for most parameters. Rotation with non-nodulating soybean without SA increased yield by 2.6 to 2.8 Mg ha−1 over continuous sorghum without SA. Rotation without SA with nodulating soybean further increased yield by 1.7 to 1.8 Mg ha−1 over rotation with non-nodulating soybean. Grain N increased by 0.5 to 1.0, 2.5 to 5.0, and 3.3 to 4.9 g kg−1 for N application to continuous sorghum and sorghum rotated with non-nodulating and nodulating soybean, respectively. Tangential abrasive dehulling device (TADD) removal indicated that continuous sorghum without SA produced the softest grain with 43 to 44% TADD removal, and sorghum rotated with nodulating soybean with manure produced the hardest grain with 22 to 27% TADD removal. As food end-use opportunities for sorghum grain evolve, use of crop rotation and SA application will be important to produce grain with desirable quality attributes. Crop Rotation and Soil Amendment Alters Sorghum Grain Quality Nanga Mady Kaye, Stephen C. Mason,* David S. Jackson, and Tom D. Galusha Dep. of Agronomy and Horticulture, and Food Science and Technology, Univ. of Nebraska, Lincoln, NE 68583-0915. Paper No. 14668 of the Journal Series of the Nebraska Agric. Res. Div. Research supported by USAID Grant No. DAN 1254-G-0021 through INTSORMIL, the International Sorghum and Millet Collaborative Research Program. Received 25 May 2006. *Corresponding author (smason1@unl.edu). Abbreviations: CS, cropping sequence; SA, soil amendment; TADD, tangential abrasive dehulling device. Grain sorghum is an important grain crop in the Central Great Plains due to its drought tolerance (Sander and Frank, 1980), high nutrient use effi ciency (Maranville et al., 1980), and use for livestock feed. During the past 50 yr, sorghum grain yields have increased by 139% largely due to improved hybrids and soil water management (Unger and Baumhardt, 1999). Due to interest in using sorghum grain for human food (Shayo et al., 2001; Johnson, 2005) and industrial products (Buff o et al., 1998, Johnson, 2005) research eff orts are presently underway to develop sorghum hybrids with improved kernel characteristics (Maunder, 2005). Rotating soybean with sorghum has been shown to increase grain yield (Gakale and Clegg, 1987; Roder et al., 1989a, Peterson and Varvel, 1989), alter soil stored water (Roder et al., 1989a), increase soil N (Bagayoko et al., 1992), improve soil physical properties (Gakale and Clegg, 1987), and reduce yield variability (Varvel, 2000). None of these studies addressed crop rotation or N supply infl uences on grain quality. One tool to help separate biologically fi xed N from other rotation eff ects is the inclusion of nodulating and non-nodulating soybean isolines into a crop rotation as previously done by Maloney et al. (1999), Gentry et al. (2001), and Bergerou et al. (2004). Manure as a soil amendment in sorghum studies has improved soil physical properties (Eghball, 2000), increased water and Published in Crop Sci 47:722–729 (2007). doi: 10.2135/cropsci2006.05.0346 © Crop Science Society of America 677 S. Segoe Rd., Madison, WI 53711 USA R e p ro d u c e d fr o m C ro p S c ie n c e . P u b lis h e d b y C ro p S c ie n c e S o c ie ty o f A m e ri c a . A ll c o p y ri g h ts re s e rv e d . CROP SCIENCE, VOL. 47, MARCH–APRIL 2007 WWW.CROPS.ORG 723 nutrient holding capacity (Sweeten and Mathers, 1985), improved soil nutrient levels (Binder et al., 2002), and increased grain yields (Roder et al., 1989a; Bagayoko et al., 1992). Nitrogen application increases yield by meeting nutrient needs of the crop. The only studies that addressed the infl uence of manure and N application on sorghum grain quality have been on N concentration of grain (Hanson et al., 1988; Kamoshita et al., 1998). Research on production practice infl uence on sorghum grain quality is limited. Kamoshita et al. (1998) and Hanson et al. (1988) found increased grain N concentration with increasing levels of N fertilizer and with rotation with soybean. Similar results have been documented in maize (Kniep and Mason, 1989; Duarte et al., 2005; Shandera et al., 1997) with an associated increase in kernel hardness and decrease in kernel breakage susceptibility with increased N supply. Johnson (2005) found that sorghum grain was harder and had lower starch content when produced under hotter and drier conditions in Texas than in Kansas and Nebraska. He attributed this to starch deposition being restricted when temperatures during grain fi ll were elevated (Tester and Karkalas, 2001). Other studies have focused on genetic diff erences infl uencing grain quality in sorghum (Rooney and Miller, 1982; O’Brien, 1999), especially protein quality (Singh and Axtell, 1973) and digestibility (Oria et al., 2000; Duodu et al., 2003). The objective of this study was to evaluate rotation with nodulating and non-nodulating soybean isolines and soil amendment application infl uences on grain yield and quality. An improved understanding of cropping practice infl uence on sorghum grain quality is important as addedvalue specialty uses for sorghum grain are developed. MATERIALS AND METHODS Research was conducted at the University of Nebraska Agricultural Research Development Center near Mead, NE on a Sharpsburg silty clay loam in 2003 and 2004. The long-term rotation study was established in 1980 and modifi ed in 1991 to incorporate nodulating and non-nodulating isolines of the soybean variety Clark. The experimental factors were cropping sequence and soil amendment. The cropping sequences were continuous sorghum, sorghum-nodulating soybean rotation, and sorghum–non-nodulating soybean rotation. The three soil amendments were zero, fresh beef feedlot manure (17.3 Mg ha on dry matter basis in 2003 and 25.9 Mg ha in 2004, applied annually in spring, and incorporated by disking), and 84 kg N ha yr for sorghum and 41 kg N ha yrfor the previous soybean crop. Nitrogen was hand-applied as NH 4 NO 3 at the V6 stage growth, which corresponds to the beginning of the stage of rapid sorghum growth and N uptake (Vanderlip, 1993). The experiment was conducted in a randomized complete block design with a split-plot treatment arrangement and four replicates. The whole plot was cropping sequence while the subplot was soil amendment. The experimental units were 9.1 m wide and 7.9 m long. For weed control, Dual-II Magnum (S-metolachlor: (1S)-2-chloro-N-(2-ethyl-6-methylphenyl)N-(2-methoxy-1-methylethyl)acetamide) was sprayed as a preemergent at a rate of 1.1 kg a.i. ha, Basagran [bentazon; 3-(1-methylethyl)-1H-2,1,3-benzonthiadiazin-4(3H)-one 2,2dioxide)] at a rate of 1.1 kg a.i. ha was applied postemergence and by hand weeding. In 2003 during grain-fi ll, grasshoppers [Melanoplus diff erentialis (Thomas)] were controlled by aerial application of Lorsban (chlorpyrifos: O,O-diethyl O-(3,5,6trichloro-2-pyridinyl) phosphorothioate) at 0.11 kg a.i. ha. The drought and lodging-tolerant sorghum hybrid DKS42– 20, with 105to 110-d relative maturity and intermediate staygreen was planted in both years. Previous crop soybean variety was Clark with a group IV maturity classifi cation and indeterminate growth habit. Tillage consisted of disking on 21 May 2003 and 27 May 2004. Crops were planted on 22 May 2003 and 27 May 2004 using a six-row John Deere 7100 maxi-merge planter ( John Deere, Moline, IL) at the rate of 39 285 kernels ha in 2003 and 32 190 kernels ha in 2004. Soil NO3–Nitrogen and Water Soils were sampled to a depth of 120 cm at planting, V6, anthesis and physiological maturity for determining soil NO 3 –N. Two soil cores for each plot were gathered using Giddings Soil probe (Fort Collins, CO) and composited. Soil samples were analyzed for soil NO 3 –N using the automated Cd reduction method analyzed by fl ow injection analysis (Gelderman and Beegle, 1998). Soil water was determined as the diff erence in soil weight at sampling, and after being oven drying at 45°C until a constant weight was reached. Treatment infl uences on soil NO 3 –N and water were presented in Kaye et al. (2007), while correlations between these soil and grain quality parameters are presented in this article. Sorghum Grain Harvest and Quality Assessment Grain yields were hand-harvested from an area of 9 m in the middle of each 12-row (8 by 9 m) plot, and were corrected to 140 g kg water content. Panicles from the harvest area were threshed, and approximately 500-g grain samples were collected and used for grain quality assessment tests. Quality parameters measured included kernel weight determined by weighing 100 kernels in duplicates, N concentration determined by Dumas method (Padmore, 1990), bulk density (test weight), true density measured on 20-g samples using a multipycnometer (Quantachrome Instruments, Boyntown Beach, FL) and TADD as recommended by Shandera et al. (1997) for maize. For the TADD test, 40 g of samples were allowed to mill for 4 min in the TADD machine equipped with an 80 grit abrasive pad (Model 4E-220, Venables Machine Works Saskatoon, Saskatoon, SK) and removal percentage was measured. High bulk and true densities, and low TADD removal indicated hard kernels desirable for dry milling and alkaline-cooked food uses (Mason and D’Croz-Mason, 2002; Shandera et al., 1997). Scanning Electron Mi