The response of grain yield to narrow rows can be analyzed in Westgate et al., 1997).terms of the effect on the amount of radiation intercepted by the crops. The objective of this work was to study the effect of row spacing There are times during the crop cycle that are most on grain yield and radiation interception (RI) during the critical period critical for yield determination. These times comprise for grain set in three crop species. Ten experiments were conducted the period bracketing flowering in maize (Kiniry and with maize (Zea mays L.), sunflower (Helianthus annuus L.), or soy- Ritchie, 1985; Fischer and Palmer, 1984) and sunflower bean [Glycine max (L.) Merr.] under irrigation or under dryland con- (Chimenti and Hall, 1992, Connor and Sadras, 1992; ditions without severe drought during flowering and grain filling. The Cantagallo et al., 1997) and extend to more advanced treatments consisted of two row distances combined with other factors reproductive stages in soybean (Shaw and Laing, 1966; such as plant density, cultivar, defoliation, etc. Grain yield responses Board and Tan, 1995; Egli, 1997). Higher crop growth to decrease distance between rows were inversely proportional to RI rates during these periods would allow more grains to achieved with the wide-row control treatment during the critical pebe set and thus higher grain yields (Andrade et al., riod for grain number determination (r 2 ϭ 0.62, 0.54, and 0.86 for maize, soybean, and sunflower, respectively). Moreover, when row 1999). Crop growth rate is directly related to the amount spacing was reduced, grain yield increases and RI increases during of radiation intercepted by the crop (Gardner et al., the critical periods for grain set were significantly and directly corre-1985). Therefore, the response of grain yield to narrow lated in the three crop species (r 2 ϭ 0.71, 0.64, and 0.94 for maize, rows can be analyzed in terms of the effect on the soybean, and sunflower, respectively). For the conditions of these amount of RI at the critical periods for kernel set. In

Maize (Zea mays L.) grain yield responds greatly to plant density (D). However, the hybrid-plant density interaction usually found is not well understood. The objective of this work was to analyze responses of different maize hybrids to D considering their biomass plasticity and reproductive partitioning. Responses to D were ana-

No abstract

No abstract

No abstract

Comparative studies indicated that mechanical impedance has the same limiting effect on root elongation Risk analysis to identify the more profitable or less risky crops in for a series of plant species including cotton (Gossypium areas with shallow soil requires quantification of yield responses to hirsutum L.), maize, wheat, and groundnut (Arachis hyphysical constraints to root penetration. Grain yield, shoot biomass, and harvest index (HI) were measured in commercial fields of indeter-pogaea L.) (Bennie, 1996). This conclusion, however, is minate soybean (Glycine max L. Merr.), maize (Zea mays L.), sunbased on the comparison of relative root elongation, flower (Helianthus annuus L.), and wheat (Triticum aestivum L.) whereas some evidence indicates substantial variation grown on Typic Argiudols and Petrocalcic Paleudols. At crop matuamong species in the absolute rate of root elongation. rity, shoots were sampled along transects (approximately 200 m) withAbsolute rates (measured at 25ЊC) ranked sunflower Ͼ soil depths between 0.35 and Ͼ1 m as determined by petrocalcic

No abstract

No abstract