Long-term Crop Rotation Study for Greenhouse gas Reduction through Agricultural Carbon Enhancement network in Lincoln, Nebraska Lincoln NE Long-term Crop Rotation Project Overview of NEMLTCRS: Long-term Crop Rotation Study (Ithaca, NE) Crop rotation and fertilizer N management are common practices that affect productivity and input use efficiency. Evaluating these practices in a long-term setting provides the opportunity to assess their influence across a wide range of growing conditions and to determine their effect on yield stability (performance across a wide range of environmental conditions). Previous publications from this experiment have evaluated the response of corn, soybean, and sorghum production to these treatments under conventional tillage during an earlier time period (e.g., Peterson and Varvel, 1989a,b,c; Varvel, 2000), concluding that diversified crop rotations generally enhance grain production. Following conversion to no-till, yield trends from 2007 to 2013 indicate that: • Diversified 2- and 4-yr crop rotations increased corn and grain sorghum yields. • Corn and grain sorghum grain yields in 2- and 4-yr rotations were more resilient to variable growing conditions.• Soybean was less sensitive than corn and grain sorghum to crop rotation. Excerpted from: Sindelar et al., 2016 (Agron. J. 108: 1592-1602) viewed as an unfassirable management practice in soybean because it can inhibit nodular:ion (Salvagiotti et aL. 2008). However. responses to early-season fertilizer N are inconsistent. For example. Varvd and Peterson (1992) reported a decrease with fertilizer N input. yet Osborne and Riedell (2006) reported a grain yield increase with fertilizer N addition. Therefore. additional work is needed to clarify this particular response of soybean to early-season N fenilization. Crop rotation and fertilizer N management arc common practices that affect productivity and input use efficiency. Evaluating these practices in a long-term setting provides the opportunity to assess their influence across a wide range of growing conditions and to determine their effect on yield stability (performance across a wide range of environmental conditions). Previous publications from this experiment have evaluated the response acorn. soybean. and sorghum produc-tion to these treatments under conventional tillage during an earlier time period (e.g.. Peterson and VarveL 1989a.b.c: Varvel. 2000). concluding that diversified crop rotations gener-ally enhance grain production. Information has not yet been reported from this study naluacing the treatments under no-till (2007-2013). To our knowledge. no studies have simul-taneously evaluated the stability of continuous and diversified rotations of corn. grain sorghum. and soybean. The objective of this study was to evaluate long-term yield performance. yield stability. and fertilizer N of corn. grain sorghum. and soybean as affected by crop rotation and fertilizer N under no-till in the western Corn Belt. MATERIALS AND METHODS A field experiment was established in 1972 on a Yuan silty clay loam-Tomek salt barn compkx (fine-silty. mired. supaac-tire. mesic Mollie Hapkidalfs and fine. smecutic. mimic Pachic Argiudolls. resik.l.didy) near Ithaca. NE (31•10'N. 96'25'W). Elevation of the site is 366 rn. and mean annual temperature and precipitation arc 10.5*C and 765 mm. respectively. In-season air temperature. soil temperature. precipitation. and open pan evaporation measured on-site during this time period arc shown in Tabk I. The experiment was a randomized complete block design in a split plot arrangement with five replications. Crop rotation was the main ploc, and fertilizer N rate was the split plot. Crop rotations included continuous crops (continuous corn (CC). continuous grain sorghum IGGI. and continuous soybean (SS]). 2-yr (CS and OS) and 4-yr crop rotations (corn-soybean-grain sorghum-ad/clover vocation ((:5C01 and corn-cut/clover - grain sorghum-soybean rotation (COGS]). Continuous rota-tions that also included a fallow treatment were established in 1972 (with three replications). In 1983. the 2- and 4-yr rotation treatments were added. fallow treaunenrs were dropped. and the experiment was expanded to five replications. For the 4-yr rota-tions, all crops were present in the roudon, but the sequences differed. Each phase of every crop rotation was present each year. Fertilizer N treatments were initiated in 1984 and included 0. 90. and 180 kg N ha-1 for corn and grain sorghum and 0.34. and 69 kg N ha-I for soybean and oat/clover. Split plots were 9 m wide (76-an nivrs.n = 12) and 10 m king. The study was annu-ally disked mice in the spring from 1983 until 2006. In 2007. the study was converted to no-till.Agronomy Journal • Volume 108. Issue 4 • 2016 1593.