Higher Population and Twin Row Configuration Does Not Benefit Strip Intercropped Corn

Increased corn (Zea mays L.) grain yield with strip intercropping, made possible because of increased edge effects, makes this soil-conserving crop production system appealing to farmers. The objective of this study was to determine the population and row configuration needed to optimize the additional yield potential in each outside corn row. Treatments \u27included: 74, 99, and 124 thousand plants ha-1 were grown in twin rows and 74 thousand plants ha-1 grown in single rows. Single rows or twin row centers were spaced 0.76 m. The experiment was conducted at four central Iowa sites during 1996 and 1997. Grain yield was not increased by increasing population, nor did it respond consistently to the twin row configuration. There was little interaction between row position in the strip and treatment response. Higher plant population decreased the number of ears per plant, kernels per row, and kernel weight. The twin row configuration increased the number of ears per plant, but this was offset by a decrease in the number of kernels per row and kernel weight. Farmers should follow current cropping recommendations until this optimum is determined. Given the inconsistent grain yield response to twin rows, there is no current rationale for investing in twin row planting equipment

Corn (Zea mays L.) Yield Response to Nitrogen Fertilizer in Conventional and Alternative Rotations

Nitrogen (N) fertilization recommendations are not available for corn in rotation with small grains or forages despite the possibility that the N response may differ from that of more conventional corn-soybean rotations. Rotations of corn with soybean (CS), corn with soybean and oat (CSO) and corn with soybean and an oat/berseem clover intercrop (CSOB) were established in 1991 and studied from 1993 through 1998 to determine the optimal N fertilization level for corn produced in each rotation. Corn in each rotation received NH4N03 applied at the rates of 0, 56, 112, or 168 kg N ha-1. Significant differences in corn grain yield occurred between rotations in three years, but no rotation was consistently superior. Corn grain yield increased with N fertilizer in each year, but in 3 of 6 years there was no advantage to applying Nat a rate greater than 112 kg ha-1. No difference in N response between rotations was observed

Tillage Effect on Soil Water Content and Soybean (Glycine max) Yield in a Strip Intercropping System

Soybean [Glycine max (L.) Merr.] response to strip-intercropping with corn (Zea may L.) and oat (Avena Jativa L.) interseeded with nondormant alfalfa (Medicago Jativa L.) may be affected by soil moisture. A three-crop strip-intercropping system of corn, soybean and oat interseeded with nondormant alfalfa was established to determine the effect of tillage system and row position on soil water content and grain yield in the soybean strip. The experiment was a split-plot design with three tillage treatments (conventional, CT; reduced, RT; and minimum tillage, MT) as main plot effects and three row positions (both edge rows and the center row) as subplot effects. In 1989 (a dry year), MT resulted in greater soil water content and soybean yield than other tillage treatments. The row bordering the oat-alfalfa strip had a lower soil water content and soybean yield than did the other two positions. Tillage did not have a significant effect in 1990 (a wet year) on soil water content or soybean yield. The 1990 soybean yield was lower in the soybean row bordering corn, but water availability did not differ significantly between row positions. MT was the most suitable tillage system for soybean production with the three-crop strip intercropping on this soil for both the wet and dry year in which this study was conducted

The Effects of Seed Size on Hybrids Formed between Oilseed Rape (Brassica napus) and Wild Brown Mustard (B. juncea)

Background : Seed size has significant implications in ecology, because of its effects on plant fitness. The hybrid seeds that result from crosses between crops and their wild relatives are often small, and the consequences of this have been poorly investigated. Here we report on plant performance of hybrid and its parental transgenic oilseed rape (Brassica napus) and wild B. juncea, all grown from seeds sorted into three seed-size categories.[br/] Methodology/Principal Findings : Three seed-size categories were sorted by seed diameter for transgenic B. napus, wild B. juncea and their transgenic and non-transgenic hybrids. The seeds were sown in a field at various plant densities. Globally, small-seeded plants had delayed flowering, lower biomass, fewer flowers and seeds, and a lower thousand-seed weight. The seed-size effect varied among plant types but was not affected by plant density. There was no negative effect of seed size in hybrids, but it was correlated with reduced growth for both parents.[br/] Conclusions : Our results imply that the risk of further gene flow would probably not be mitigated by the small size of transgenic hybrid seeds. No fitness cost was detected to be associated with the Bt-transgene in this study