1960; Walton, 1975; Carr et al., 1998; Chapko et al., 1991). Robinson (1960) reported that pea improved oat (Avena Intercropping barley (Hordeum vulgare L.) with Austrian winter sativa L.) forage yield. In a 2-yr pea-barley and pea-oat pea (Pisum sativum ssp. arvense L. Poir) may increase the use efficienintercropping study, Carr et al. (1998) found that total cies of growth resources and reduce fertilizer N requirements. The forage yield was unaffected by intercropping when the objectives of this study were to determine (i) row configuration and (ii) fertilizer N effects on yield, protein content, and the land equiva-cereal crop was sown at a rate equal to or greater than lent ratio (LER) of barley-pea intercropping systems. A 3-yr barleythe sole crop seeding rate. However, less forage was pea intercropping study was conducted at the Western and Central produced when the cereal component was sown at half Agricultural Research Centers (WARC and CARC) of Montana State the sole crop seeding rate. They also found that the University from 2000 to 2002 with three row configurations (4 rows intercropping forage yield was unaffected by the pea barley ϫ 4 rows pea, 2 rows barley ϫ 2 rows pea, and barley-pea mixed seeding rate. In other studies, forage and grain yield of within rows) and three N application treatments (0, 67, and 134 kg legumes were suppressed by cereal components (Ofori N ha Ϫ1 ). Barley biomass production increased 41% at WARC and and Stern, 1987; Hauggaard-Nielsen and Jensen, 2001; CARC, whereas pea biomass production decreased 34% at WARC Hauggaard-Nielsen et al., 2001). Seeding rates for comand 46% at CARC with the row configuration changing from the 4 ϫ 4 ponent crops in cereal-pea mixtures are commonly less to the mixed configuration. The LER ranged from 1.05 to 1.24 on a biomass basis and from 1.05 to 1.26 on a protein basis, indicating a than when either the cereal crop or pea is sown alone production advantage of intercropping. Barley is a more competitive (Carter and Larson, 1964; Droushiotis, 1989). component than pea. Separated row arrangements are advantageous The efficiency of an intercropping system can be evalwhere the desired outcome is a greater pea component in the harvested uated by the land equivalent ratio (LER), defined as forage, but the mixed arrangement has a greater total biomass yield the total area required under sole cropping to produce and LER. Fertilizer N increased total biomass yield and protein level the equivalent yields obtained under intercropping (De in barley-pea intercrops, but high N rates could decrease the LER Wit and Van Den Bergh, 1965; Willey, 1979; Mohta and and result in toxic levels of nitrate in the forage. De, 1980). It is expressed as:
Annual legume plowdown systems, which utilize fall regrowth for N contributions to rotational crops, have not been adapted to irrigated, intermountain areas of the Northern Rockies. Our objective was to evaluate plowdown systems using ‘Nitro’ alfalfa (Medicago sativa L.) and ‘Bigbee’ berseem clover (Trifolium alexandrinum L.). These two legumes were grown under five harvest management systems (zero to three forage harvests prior to fall plowdown of regrowth, or a standard three harvest system with no herbage plowdown) at two sites in western MT differing in soil characteristics. They were assayed for forage and plowdown production and for N benefits to ‘Clark’ barley (Hordeum vulgare L.; syn. H. distichon L.) for two subsequent years. Maximum herbage plowdown N was 125 to over 200 kg N ha−1 for berseem clover and 87 kg N ha−1 for alfalfa. A two‐harvest system resulted in 3.6 to 6.6 Mg ha−1 forage and 45 to 78 kg N ha−1 in herbage plowdown. Effects of plowdown were measured directly in increased soil N availability and correlated increases in N uptake in subsequent barley; benefits were expressed in increased grain yields and/or grain N concentrations and were apparent for two successive years at the site of lower native fertility. Alfalfa N benefits were superior to berseem clover, though disproportionate to herbage plowdown N quantities, possibly due to greater root and crown N in alfalfa. Where the management goal is primarily forage production with moderate benefit of plowdown N, berseem clover works well in a two‐harvest system; Nitro alfalfa is preferred where greater benefits of plowdown N are desired.
Rapid development of the Montana pulse crop industry has created a strong demand for breeding efforts and cultivar recommendations. We evaluated adaptation and yield stability of diversely sourced dry pea (Pisum sativum L.) and lentil (Lens culinaris Medik.) genotypes across Montana from 2009 to 2011. Mega‐environments in Montana and superior genotypes were identified using additive main effect and multiplicative interaction (AMMI) methodology. Grain yield of both crops varied among the locations and across years. A large portion of the total variation (genotype [G] and environment [E] plus their interaction G × E) was explained by E (93% for dry pea and 89% for lentil), while G only explained 0.7% and 3.6% of the total variation for dry pea and lentil, respectively. Dry pea cultivars Delta, Majoret, and Cruiser were found to be suitable, with general adaptation to Montana. Three mega‐environments were identified for pea including: (i) Richland (northeastern Montana); (ii) Bozeman, Conrad, and Corvallis (southwestern and western Montana); and (iii) Havre, Moccasin, and Huntley (northern, central, and southern Montana). Among lentil cultivars, CDC Richlea was judged as the most promising cultivar as a result of general adaptation. Lentil cultivars Essex and LC01602300R showed higher yield potential than CDC Richlea but more specific adaptation. Four mega‐environments were also distinguished for lentil including (i) Creston and Conrad (northwestern Montana), (ii) Havre and Richland (northern and northeastern Montana), (iii) Moccasin (central Montana), and (iv) Huntley (southern Montana).
Suitable plant diagnostic procedures for nitrogen (N) management in high input crops such as potato (Solanum tuberosum) and peppermint (Piper mentha) should be derivative [measuring instantaneous nitrogen (N) uptake] rather than integrative (total accumulation) and should reflect concurrent soil N availability. Analyses for dry matter or sap nitrate (NO 3 ) in potato petioles or peppermint stems are proposed as derivative procedures, but the plant-soil NO 3 relations of these analyses are not well understood. Our objectives were to test the validity of these derivative plant diagnoses as measures of concurrent uptake against the Michaelis-Menten model of saturation kinetics. Periodic measures of dry matter and sap NO 3 in potato petioles and peppermint stems were taken from field experiments with various rates and timings of N fertilizer, and regressed against concurrent soil NO 3 (0-30 cm) by nonlinear least squares fit to the model:where: V = potato petiole or peppermint stem NO 3 in the dry plant tissue or fresh sap, SN = extractable soil NO 3 , and V max and Ks are constants. Sap NO 3 adhered to the model well for both species (R 2 values of 0.74 for potato and 0.61 1. 470WESTCOTT, KNOX, AND WRAITH for peppermint), with similar values for V max (2314 mg NO 3 -N/kg for potato and 2187 mg NO 3 -N/kg for peppermint). Peppermint exhibited a greater value for Ks than potato, indicating a lesser affinity for available soil N. Dry matter NO 3 also fit the model well for potato (R 2 = 0.79) but not peppermint (R 2 = 0.22). Values for SN opt , the level of soil NO 3 required to maintain critical levels of plant NO 3 , were calculated from the regressions using previously established plant criteria. Under continuous N fertilization, values for SN opt ranged from 5.5 to 8.5 kg NO 3 /kg, were similar between species and were sensitive to variances in plant criteria. The kinetic model provides a mechanistic basis for derivative plant diagnosis methods. Sap analysis has several advantages to recommend it as a derivative procedure: sap-soil nitrate relations adhere well to a kinetic model, kinetic parameters are consistent between species, and data can be readily collected on site. INTRODUCTIONPlant NO3 analysis is widely accepted as a diagnostic tool for N management in potato (1,2) and may be applicable to peppermint (3). These shallow-rooted crops receive high inputs of N and water under intensively managed systems that are amenable to plant diagnostic approaches. For instance, the prevalent practice of frequent midseason N application through irrigation systems lends itself well to rate adjustment in response to crop-N status. Refinements in diagnostic technique are compelled by concerns over N utilization efficiency and NO3 leaching in these crops.Tissue testing is the on-site analysis of sap expressed from fresh plant tissues. As a diagnostic technique, it has the advantage of immediacy over plant analysis, the laboratory determination of nutrient content in dried plant samples. The disadvantage is that the semiquanti...
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