Maize hybrids that yield well, mature earlier with low grain moisture contents, tolerate higher population densities and take advantage of narrow row spacings better than the currently available hybrids would be more suitable for production in short-season areas. Leafy reducedstature maize hybrids, which have only recently been developed, have traits which address these criteria. The objective of this study was to evaluate the effects of different population densities (65 000 and 130000 plants ha"') and planting patterns (single rows 76 cm apart and paired rows with 20 cm between rows within a pair of 56 cm between rows of adjacent pairs) on the yield and yield components of two leafy reduced-stature (LRSl and LRS2), one non-leafy reduced-stature (NLRS), and two conventional corn hybrids (Pioneer 3979, <2500 CHU; and Pioneer 3902, 2600-2700 CHU) at two locations. All hybrids had higher kernel numbers per row and single plant grain yields at the lower population densities when in paired rows. However, as plant density increased, these variables decreased more in the conventional hybrids than the LRS and NLRS hybrids, which demonstrates the greater tolerance of the latter to the stresses associated with higher plant densities. Grain yield was higher for the two LRS hybrids and the NLRS hybrid at 130000 plants ha~' than 65000 plants ha '. Grain yield of conventional hybrids was reduced at the higher population density. The LRS hybrids matured before both conventional hybrids and out yielded Pioneer 3979 at the higher plant population density in both row spacings at both sites. Harvest index was not affected by population density and this value was not different among the NLRS and conventional hybrids. However, the harvest index of the LRS hybrids was greater than the others. LRS and NLRS hybrids had lower moisture contents and earlier maturities than conventional hybrids. Rapid growth of the first ear and higher harvest index values might are indications that LRS hybrids are more tolerant of higher population densities than the conventional hybrids.
Th e importance of saffl ower (Carthamus tinctorius L.) is increasing as a low input, stress-tolerant oilseed crop around the world. Adapting a crop growth model for saffl ower will help to assess the feasibility of this crop under diverse environmental conditions with relatively limited fi eld experimentation. Th e objective of the project was to adapt the Decision Support System for Agrotechnology Transfer (DSSAT) Cropping System Model (CSM-CROPGRO) to simulate growth and seed yield of spring saffl ower. Th e CROPGRO template approach was used, and parameters in species and cultivar fi les were developed based on saffl ower literature and calibration to fi eld data. Th e entered base temperatures for photosynthetic, vegetative, and reproductive processes of saffl ower ranged from 0 to 5°C while corresponding optimum temperatures varied from 19 to 40°C. Simulated results were compared with observed data collected from fi eld experiments conducted at Clovis, NM, during 2013 and 2014. Th e model predicted the crop life cycle (anthesis and harvest maturity date) with relative root mean square error (RRMSE) of 0.07. Average plant biomass, head mass, head number and seed number were satisfactorily simulated when compared to observed values. Seed yield, averaged over irrigation treatments and years, was predicted as 1963 kg ha -1 compared to measured value of 1902 kg ha -1 with RRMSE of 0.12. Reasonable prediction of phenology, growth, and yield by the model adapted for saffl ower suggested that the CROPGRO-saffl ower model is promising to simulate saffl ower production in semiarid climates. However, further testing of the CROPGROsaffl ower model under diff erent environments is needed.
Field experiments were conducted in 1996, 1997, and 1998 at Ste. Anne de Bellevue, Quebec, Canada, and in 1996 at Ottawa, Ontario, Canada, to quantify the impact of corn hybrids, differing in canopy architecture and plant spacing (plant population density and row spacing), on biomass production by transplanted and naturally occurring weeds. The treatments consisted of a factorial combination of corn type (leafy reduced stature [LRS], late-maturing big leaf [LMBL], a conventional Pioneer 3979 [P3979], and, as a control, a corn-free condition [weed monoculture]), two weed levels (low density [transplanted weeds: common lambsquarters and redroot pigweed] and high density [weedy: plots with naturally occurring weeds]), two corn population densities (normal and high), and row spacings (38 and 76 cm). At all site-years under both weed levels, the decrease in biomass production by both transplanted and naturally occurring weeds was greater due to the narrow row spacing than due to the high plant population density. The combination of narrower rows and higher population densities increased corn canopy light interception by 3 to 5%. Biomass produced by both transplanted and naturally occurring weeds was five to eight times less under the corn canopy than in the weed monoculture treatment. Generally, weed biomass production was reduced more by early-maturing hybrids (LRS and P3979) than by LMBL. Thus, hybrid selection and plant spacing could be used as important components of integrated pest management (weed control) for sustainable agriculture.
Core Ideas Canola forage production was higher than wheat in fall but not in later harvests. Many of the forage quality parameters were superior in canola compared with wheat. Forage harvest decreased canola yield even before bolting but not in wheat. Canola has dual‐purpose use potential (forage and seed yield) with LF harvest. Winter canola (Brassica napus L. biennus) has the potential to be a dual‐purpose crop in the US Southern Great Plains, a region with cereal fallow mono‐cropping. However, there is little information on dual‐purpose canola in the region. Therefore, field studies were conducted in Clovis, NM, in 2013, 2014, and 2015 to compare harvesting time effect on forage productivity (dry matter), quality, and oil and seed production of canola and wheat. Harvesting time treatments were late‐fall (LF), mid‐winter (MW), early‐spring (ES), late‐spring (LS), and no‐harvest (NH). The two forage crops were canola (cv. DKW44‐10, Griffin, and Safran) and wheat (cv. TAM 111 and TAM 113). In general, crop dry matter increased and forage nutritive values decreased with delay in harvest. Dry matter of LF to ES harvests ranged from 2950 to 7740 (canola) and from 2390 to 7490 kg ha−1 (wheat), suggesting superior forage production of canola with LF to ES harvests. Crops had similar crude protein and acid detergent fiber. Canola's neutral detergent fiber was lower (238 vs. 425 g kg−1), whereas its relative feed value (188–425) was higher than wheat (127–204). Average canola seed yields (excluding 2014) were 4360, 3040, 2940, and 2720, 930 kg ha−1 with the NH, LF, MW, ES, and LS forage harvests, respectively. Forage harvest had inconsistent effects on wheat seed yield. These results show canola's potential to produce high‐quality forage and seed yield and indicate that canola can be used as a rotational break crop in the crop–livestock production systems of the Southern Great Plains.
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