Effect of Tillage and Nitrogen Rate on Corn Yield and Nitrogen and Phosphorus Uptake in a Corn-Soybean Rotation

Understanding tillage, N, and P interactions can contribute to improved N and P utilization and crop response. This study examined the interaction effects of tillage and N rate of two N sources on N and P uptake by corn (Zea mays L.). The study was conducted on Kenyon loam (fine loamy, mixed, mesic Typic Hapludolls) soil at the Iowa State University Northeast Research and Demonstration Farm near Nashua, IA. A randomized complete block design with a split-plot arrangement in three replications was used for the two separate N source experiments. The tillage systems consist of no-tillage (NT), strip-tillage (ST), and chisel plow (CP) as main plots. Within each tillage four N rates (0, 85, 170, and 250 kg N ha) were assigned as subplots for each N source of manure (total N) and fertilizer (anhydrous ammonia) in a corn-soybean [Glycine max (L.) Merr.] rotation. Tillage and increase in N rate beyond 85 kg ha21 had no effect on corn grain yield with both N sources. Tillage 3 N rate had a significant effect on plant N and P uptake, especially at early growth stages with both N sources. Recovery percentage of applied N across all tillage systems and N rates was 40% and 27% for manure and fertilizer sources, respectively, at the 12th-leaf growth stage of corn (V12). Plant N and P uptake at V12 growth stage was 44% and 37%, respectively, across tillage systems, N sources, and N rates. The findings indicate that the N rate and seasonal variability have more influence on plant N and P uptake than does the tillage system. SOIL TILLAGE AND FERTILITY MANAGEMENT influence both nutrient and soil moisture dynamics in the soil– plant system, which in turn affect nutrient use efficiency in a cropping system. Some of the tillage functions are to incorporate fertilizer and crop residues in the soil, improve soil aeration, and subsequently promote organic N and P mineralization (Carter and Rennie, 1987; Dinnes et al., 2002; Groffman et al., 1987; House et al., 1984; Huntington et al., 1985; McCarthy et al., 1995; Rice et al., 1987; Varco et al., 1993; Yoong et al., 2001). The tillage system can influence soil N availability due to its impact on soil organic C and N mineralization and subsequent plant N use or accumulation (Dinnes et al., 2002; Al-Kaisi and Licht, 2004; Licht and Al-Kaisi, 2005a; Gilliam and Hoyt, 1987; Mehdi et al., 1999; Sanju and Singh, 2001). Compared with NT, the conventional tillage (CT) system can significantly change the mineralizable C and N pools (Woods and Schuman, 1988). However, a long-term NT system has potentially greater mineralizable C and N pools compared with CT (Doran, 1980). The plant N use can be altered by the different management practices and interactions between tillage system, N rate, and N application timing. The interactive effects of different tillage systems, such as, NT, CT, or minimum tillage and N rate on grain N uptake was significant in increasing N removal with increasing N rate (Halvorson et al., 2001). Similarly, corn response to other management practices, such as the use of starter fertilizer with CT and ST systems, showed that corn silage and grain yields in CT systems were lower than those in ST; however, both silage and grain yields of both tillage systems increased with additional N applications (Mullins et al., 1998). An understanding of tillage and N source effect on the dynamics of N availability in soil and plant N uptake through the growing season at different growth stages is essential for determining the efficiency of N management. As the N availability is affected by the tillage system, P availability can equally be affected, leading to a P deficiency in many cropping systems. Many soils have large reserves of total P, but low levels of available P (Ortiz-Monasterio et al., 2002). On soils testing low in available P, application of P fertilizer or liquid manure can increase crop yields, especially for corn and soybean (deMooy et al., 1973; Mallarino et al., 1991; Obreza and Rhoads, 1988; Webb et al., 1992). However, plant P uptake varies with soil P and moisture availability, and the concentration of P in plant tissue decreases with plant age and water stress (Payne et al., 1995). It was found that banded P (deep or shallow) increased early corn growth and P uptake compared with broadcast placement with NT (Mallarino et al., 1999). Liquid manure can be a valuable source for plant P nutrient need. In a study comparing liquid swine manure with chemical N and P fertilizer sources, it was found that corn yield and N and P uptake was similar for both N sources (Al-Kaisi and Waskom, 2002). The value of liquid manure as a nutrient source to plant growth and the proximity of such source to field crop production can help reduce the cost of corn production as producing and transporting chemical fertilizers is costly. Therefore, this research explored this alternative source for N and P. Information on tillage and N source effects on N and P use efficiency in corn is limited. Our objective was to examine the interactive effects of three tillage systems (NT, ST, and CP) and four N rates of liquid swine manure and N fertilizer on corn response and N and P use efficiencies. MATERIALS AND METHODS