High Input Treatment Research Articles

Assessing the impact of high-input management for reducing soybean yield gaps on high-productivity farms

To increase soybean actual yields (Ya), modern farmers are interested in exploring novel intensification options. We hypothesize that the inclusion of a high-input treatment in high-productivity systems may potentially reduce yield gaps (Yg), representing additional profits for farmers. Our objectives were to: (i) estimate Ya, water-limited yield potential (Ywlim), and Yg; (ii) evaluate a high-input treatment as a management option for reducing Yg; (iii) identify management and environmental factors associated to yield response to inputs and, (iv) determine the economic outcome of this high-input management on high-productivity soybean crops. We carried out 27 on-farm field experiments comparing a conventional management system versus a novel high-input treatment across the Central Pampas of Argentina. The conventional treatment was the most common management prescribed by farmers in the region. The high-input treatment included a set of inputs that were not usually applied and involved soil fertilizers with S and Zn, seeds treated with insecticides, fungicides, and inoculants, stress-reducing product, Ca and B foliar fertilizers and preventive insecticide. The Ywlim was estimated using crop simulation models. Yield gaps were calculated as the difference between Ywlim and Ya. Average Ya and Ywlim were 4571 and 5100 kg ha−1, respectively, with a Yg lower than 30%. High-input treatments promoted a yield response of 131 kg ha−1 across sites (p < 0.001), reducing Yg by 2.6%. Yield response to high-input treatment was positively correlated with Yg and soil pH, but negatively correlated with soil P. No positive economic outcomes were obtained with the high-input treatment. This study showed low benefits of the high-input treatments for reducing Yg in high-yielding soybeans managed by high-productivity farmers. Future yield increases in this type of systems would rely on genetic improvement of soybean yield potential and exploiting genotype x management x environment interactions.

Low-input cultivation of camelina (&lt;em&gt;Camelina sativa&lt;/em&gt; (L.) Crantz) in a Mediterranean semi-arid environment

The cultivation of oil crops for biofuel production has often been accused of not being environmentally sustainable due to the high inputs needed. To explore the effect of reduced input on productive and qualitative traits of camelina (Camelina sativa (L.) Crantz), a trial was carried out over a two-year period. This study analysed two different levels of input: a low input treatment (shallow non-inversion tillage and low fertilisation rate) and a high input treatment (deeper tillage and high fertilisation rate). Camelina was positively, even though to a limited extent, affected by high input treatment as highlighted by the increase in seed yield (from 1.8 to 2.0 t ha–1), crop residues (from 4.8 to 5.2 t ha–1), seed protein content (from 26.5 to 28.9%), seed oil content (from 41.5 to 43.4%) and oil yield (from 0.75 to 0.88 t ha–1). So, from a sustainable point of view, we must consider negligible the effect of high input and satisfactory the performances of camelina in the low input regime. Low input management resulted in satisfactory yields in terms of both quantity and quality, results which were not very different from high input, indicating promising potential for conservation agriculture practices in camelina in a semi-arid environment.&#x0D; Highlights - Camelina showed high adaptability to conservation agriculture practices. - Seed yield of 1.9 t ha–1 was obtained under reduced tillage and low fertilisation rate. - High inputs (fertilisation and tillage) determined a 12-d longer crop cycle. - α-linolenic, erucic and eicosenoic acids were affected by input levels.

The effects of various plant protection methods on the development of Zymoseptoria tritici and Cephalosporium gramineum, grain yield and protein profile

ABSTRACTSeptoria leaf blotch progresses rapidly, leading to the development of Zymoseptoria titici forms resistant to fungicides. Cephalosporium stripe is caused by Cephalosporium gramineum. The aim of this study was to evaluate the effectiveness of selected pesticides in limiting the symptoms of both diseases on winter wheat leaves, and to determine their influence on grain yield and the content and composition of protein fractions in wheat kernels. Propiconazoles were most effective in inhibiting the development of Septoria leaf blotch (symptoms were reduced from 54.7% to 78.6%). Strobilurins were less effective due to the presence of isolates with the G143A mutation. Symptoms of Cephalosporium stripe were rarely observed, and protective treatments did not reduce their severity. The highest content of grain protein (14.81%) was found in plants most intensely protected with the fungicides containing fenpropimorph, pyraclostrobin and epoxiconazole. The principal component analysis revealed that the plant protection method influenced the grain protein profile. The accumulation of HMW glutenins and α/β gliadins was mutually interrelated and higher in high-input treatments; control grain was characterized by close relationships between ω-gliadins, LMW glutenins, albumins and globulins, whereas low-input treatments influenced mostly γ-gliadins.

Functional response of leaf- and planthoppers to modern fertilisation and irrigation of hay meadows

In the drier regions of the European Alps, traditional land-use of montane and subalpine meadows, i.e. extensively managed with solid manure application and irrigation via water channels, is currently shifting towards application of slurry and aerial irrigation. The impact of these new practices upon biodiversity remains poorly understood and calls for quantitative assessments of their effects. Relying on a full block design, we tested the effects of six management treatments corresponding to an increasing gradient of farming intensification (fertilisation with slurry and/or irrigation with sprinklers) on Auchenorrhyncha (Hemiptera) communities occurring in the inner Swiss Alps. The experimental set up consisted of: control plots (no fertiliser, no irrigation; C-plots); plots that received only fertiliser (F-plots); plots that were only irrigated (I-plots); and plots that received low-, medium- and high-input of fertiliser and water (F+I 1/3-plots; F+I 2/3, F+I 3/3-plots; 3/3 corresponds here to the input level necessary for achieving maximum theoretical hay yield locally). After two years of experimental treatment (2012), plots that were only fertilised or only irrigated showed no change in the population sizes of Auchenorrhyncha, while plots that received low-, medium- and high-input of fertiliser and water harboured significantly higher abundances (1.9, 1.5 and 1.4 times higher, respectively), biomass (1.8, 1.6 and 1.8 times higher, respectively), as well as species richness (+27–30%, on average) than control plots. Abundances and species richness were also higher in plots with low-input of fertiliser and water compared to fertilised only plots. Monophagous and oligophagous species were most abundant in plots with low-input of fertiliser and water. Medium- and high-input treatments (F+I 2/3 and 3/3) increased the number of generalist (eurytopic) species, while only low-input treatment (F+I 1/3) boosted the more specialised (stenotopic) species. This provides support to the hump-shaped diversity-disturbance relationship and guidance for sustainable management of biodiversity-rich mountain hay meadows.

Effects of 42-year long-term fertilizer management on soil phosphorus availability, fractionation, adsorption–desorption isotherm and plant uptake in flooded tropical rice

Soil phosphorus (P) fractionation, adsorption, and desorption isotherm, and rice yield and P uptake were investigated in flooded tropical rice (Oryza sativa L.) following 42-year fertilizer and manure application. The treatments included low-input [unfertilized control without N, P, or K (C0N0)], farmyard manure (FYM) (C1N0), NP (C0NP), NPK (C0NPK), FYM+NP (C1NP), and high-input treatment, FYM+NPK (C1NPK). Grain yield was increased significantly by 74% over the control under the combined application of FYM+NPK. However, under low- and high-input treatments, yield as well as P uptake was maintained at constant levels for 35years. During the same period, high yield levels and P uptake were maintained under the C0NP, C0NPK, and C1NPK treatments. These are unique characteristics of a tropical flooded ecosystem, which is a self-sustaining system for rice production. The Fe–P fraction was highest compared to the Ca–P and Al–P fractions after 42years of fertilizer application and was significantly higher under FYM+NPK treatment. The P adsorption capacity of soil was highest under the low-input treatment and lowest under long-term balanced fertilization (FYM+NPK). In contrast, P desorption capacity was highest under NPK and lowest in the control treatment. Long-term balanced fertilization in the form of FYM+NPK for 42years lowered the bonding energy and adsorption capacity for P in soil but increased its desorption potential, increasing P availability to the plant and leading to higher P uptake and yield maintenance.

Bread wheat performance, fusarium head blight incidence and weed infestation response to low-input conservation tillage systems in eastern Canada

Munger, H., Vanasse, A., Rioux, S. and Legere, A. 2014. Bread wheat performance, fusarium head blight incidence and weed infestation response to low-input conservation tillage systems in eastern Canada. Can. J. Plant Sci. 94: 193-201. Bread wheat performance, the incidence of diseases like fusarium head blight (FHB) and weed infestations may be affected by low-input systems and conservation tillage practices. This 2-yr study assessed the effects of three 24-yr-old tillage treatments (MP: moldboard plow; CP: chisel plow; NT: no-till) and two cropping systems (high-input: herbicide and mineral fertilizer; low-input: mechanical weed control and organic fertilizer) on wheat productivity, deoxynivalenol (DON) content, Fusarium graminearum inoculum production, and weed infestation in hard red spring wheat. In 2009, low-input CP and NT yields were 13 and 31% lower, respectively, than low-input MP yield, which was comparable with all of the high-input treatment yields. In 2010, yields were 23% lower in CP and NT ...

Bread wheat performance, fusarium head blight incidence and weed infestation response to low-input conservation tillage systems in eastern Canada

Munger, H., Vanasse, A., Rioux, S. and Légère, A. 2014. Bread wheat performance, fusarium head blight incidence and weed infestation response to low-input conservation tillage systems in eastern Canada. Can. J. Plant Sci. 94: 193–201. Bread wheat performance, the incidence of diseases like fusarium head blight (FHB) and weed infestations may be affected by low-input systems and conservation tillage practices. This 2-yr study assessed the effects of three 24-yr-old tillage treatments (MP: moldboard plow; CP: chisel plow; NT: no-till) and two cropping systems (high-input: herbicide and mineral fertilizer; low-input: mechanical weed control and organic fertilizer) on wheat productivity, deoxynivalenol (DON) content, Fusarium graminearum inoculum production, and weed infestation in hard red spring wheat. In 2009, low-input CP and NT yields were 13 and 31% lower, respectively, than low-input MP yield, which was comparable with all of the high-input treatment yields. In 2010, yields were 23% lower in CP and NT compared with MP, and 32% lower in low-input than in high-input systems. Optimum wheat yield in low-input systems appeared conditional to adequate weed control, which was achieved with MP and CP tillage. Protein content, test weight, and 1000-kernel weight were higher in the high-input system than in the low-input system, except for test weight in 2009. DON content was not affected by tillage in either year, and was lower in low-input system than in high-input system in 2009. Fusarium graminearum inoculum measured in 2009 was similar across tillage treatments in the high-input system, whereas in the low-input system, the inoculum was lower in NT than in MP. In 2010, DON content was not affected by any treatment. Hot and dry conditions were not conducive to pathogen development, and may explain the low level of DON and the lack of treatment effect.

High-yield no-till canola production on the Canadian prairies

Harker, K. N., O'Donovan, J. T., Turkington, T. K., Blackshaw, R. E., Lupwayi, N. Z., Smith, E. G., Klein-Gebbinck, H., Dosdall, L. M., Hall, L. M., Willenborg, C. J., Kutcher, H. R., Malhi, S. S., Vera, C. L., Gan, Y., Lafond, G. P., May, W. E., Grant, C. A. and McLaren, D. L. 2012. High-yield no-till canola production on the Canadian prairies. Can. J. Plant Sci. 92: 221–233. Relatively high prices and increasing demand for canola (Brassica napus L.) have prompted growers to produce more canola on more cropland. Here we determine if canola seed yield and oil concentration can be increased over current levels with high levels of crop inputs. From 2008 to 2010, direct-seeded experiments involving two seeding rates (75 vs. 150 seeds m−2), two nitrogen rates (100 vs. 150% of soil test recommendation), and the presence or absence of polymer-coated nitrogen or fungicides, were conducted at eight western Canada locations in canola-wheat-canola or continuous canola rotations. Herbicides, insecticides and fertilizers other than nitrogen were applied as required for optimal canola production. Increasing recommended nitrogen rates by 50% increased canola yields by up to 0.25 Mg ha−1. High (150 seeds m−2) versus lower (75 seeds m−2) seeding rates increased canola yields by 0.07 to 0.16 Mg ha−1. Fungicide treatment or polymer-coated nitrogen blended with uncoated urea increased canola yields by 0.10 Mg ha−1 in 2010, but not in 2008. The highest canola input combination treatment following wheat (3.50 Mg ha−1) yielded substantially more than the same high input treatment following canola (3.22 Mg ha−1). Average site yields were influenced by site conditions such as soil organic matter, days to maturity, and temperature, but these site and environmental predictors did not alter treatment rankings. Using higher than the soil test recommended rate of nitrogen or planting 150 versus 75 seeds m−2 increased canola yields consistently across western Canada. Canola oil concentration varied among canola cultivars, but was consistently low when N rates were high (150% of recommended). Higher than normal seeding rates led to high canola seed oil concentration in some cases, but the effect was inconsistent.

Effective use of water by wheat varieties with different root system sizes in rain-fed experiments in Central Europe

Abstract Effective use of water (EUW) was evaluated along with grain yield in the same environment over different years and locations. The root system sizes of sets of winter wheat varieties (20, 20, 20 and 18 varieties in 2007, 2008, 2009 and 2010, respectively) were evaluated by measuring their electric capacity. The RSS results were compared with the yield and grain quality in official variety trials at 20, 22, 23 and 23 stations in 2007, 2008, 2009 and 2010, respectively. All varieties were tested under two conditions with low and high inputs, and in some years they were also tested after late sowing and after unsuitable forecrops at a few stations. The RSS was mostly controlled by the location; the varieties differed significantly, explaining 2.6–15.6% of the variation in RSS, while 1.7–3.9% of the total variation was unexplained. In 2007, a dry year, the RSS was significantly correlated with yield in both variants ( r 2 = 0.285* and 0.284*, respectively) and with yield of starch ( r 2 = 0.248*) at all stations. In 2008, the highest-yielding year, the correlation of RSS with yield at the three stations at the lowest altitude and with the highest temperature was negative ( r = −0.459*). In 2009, the yield was highly significantly correlated at only five locations in medium altitudes, where drought occurred, only in the high input treatment ( r 2 = 0.391**). No relationship between RSS and yield was found in the wet year 2010. The third of the varieties with the greatest RSS had an RSS that was 21% greater than those of the one-third of varieties with the smallest RSS in 2007 and a grain yield 420 kg ha −1 higher. The difference responded to additional use of about 7 mm of subsoil water. The most contrasting varieties showed a yield difference of 860 kg, i.e., approximately 15 mm of subsoil water. We conclude that differences in the EUW expressed as different yields under the same conditions can be partly attributed to different RSSs (probably due to deeper rooting) and can be improved by breeding.

Role of host and environment in mediating reduced gastrointestinal nematode infections in sheep due to intensive rotational grazing

We have previously reported marked reductions in faecal worm egg counts (WECs) and drenching frequency in sheep on an intensive rotational grazing system (IRG) in a cool temperate environment with summer-dominant rainfall. These experiments were designed to determine the role of the host and environmental factors in mediating this. The role of host factors was investigated by administering a fixed larval challenge in each of the 4 seasons of the year to groups of 20 young sheep on three different management systems, including IRG. This comprised a mixed larval challenge containing infective larvae of Haemonchus contortus and Trichostrongylus colubriformis 7 days after short-acting anthelmintic treatment. A range of measurements was then made up to day 35 post-challenge. The role of environmental factors was determined by assessing pasture infectivity in four seasons using faecal worm egg counts (WECs) and pooled faecal culture of worm-free tracer sheep. The management systems were high input (HI) with high fertiliser inputs high stocking rate and relatively long grazing periods; typical New England management system (TYP) with moderate fertiliser inputs and stocking rate and relatively long grazing periods and; Intensive rotational grazing (IRG) with moderate fertiliser inputs and stocking rate but very short (mean 5 days) grazing periods and long (mean 103 days) rest periods. IRG sheep had higher mean WEC at 28 and 35 days after fixed larval challenge than HI and TYP sheep in spring (IRG: 9500±1000; HI: 4000±1000; TYP: 7200±1000 eggs/g, P<0.01) and summer (IRG: 8400±750; HI: 5300±800; TYP: 4400±700 eggs/g; P<0.001) and also had lower liveweights during these seasons. There was no difference in WEC after the autumn challenge (IRG: 5100±450 HI: 4500±450; TYP: 4200±450 eggs/g; P∼0.36) but IRG had lower WEC than TYP following the winter challenge (IRG: 2900±400; HI: 2300±400; TYP: 4300±400eggs/g, P<0.01). The tracer sheep (used to determine pasture infectivity) on IRG had significantly lower WECs during winter, spring and summer than those under the other management systems. Faecal culture and larval differentiation revealed that faeces from tracers on IRG contained significantly lower proportions of H. contortus and significantly higher proportions of Trichostrongylus spp. and Teladorsagia circumcincta than faeces from tracers on the HI and TYP treatments. Thus, when IRG was most efficacious for worm control, during spring and summer when short graze and long rest periods were maintained, sheep on this system exhibited greater susceptibility to larval challenge while tracer sheep indicated lower pasture infectivity. This demonstrates that the effects of IRG on WEC are mediated by reduced larval challenge rather than increased host resistance to infection.

Effects of input management and crop diversity on economic returns and riskiness of cropping systems in the semi-arid Canadian Prairie

AbstractProducers in the semi-arid Dark Brown Chernozemic (Typic Boroll) soil zone of the Canadian Prairie are contemplating changes to land-use practices, moving away from conventional high-input production systems that specialize in one or two annual grain crops to more diversified and extended cropping systems that use reduced-input and organic management practices. This study examined the economic merits of nine cropping systems, consisting of a factorial combination of three input management methods and three levels of cropping diversity. It was conducted over the 1996–2007 period on a loam soil at Scott, Saskatchewan. The input treatments were: (1) high input (HIGH), which used conventional tillage and full recommended rates of fertilizers and pesticides ‘as required’; (2) reduced input (RED), which used conservation tillage and integrated weed and nutrient management practices in an effort to lower requirements for fuel, fertilizers and pesticides; and (3) organic input (ORG), which used tillage, non-chemical pest control, higher seeding rates, delayed seeding and legume crops to replenish soil nutrients. The crop diversity treatments included: (1) a fallow-based rotation with low crop diversity (LOW); (2) a diversified annual rotation of cereal, oilseed and pulse grains (DAG); and (3) a diversified rotation using annual grains and perennial forages (DAP). All crop rotations were 6 years in length. At the 2007 input costs and prices, average net returns and 12-year net present values were higher for organic than for non-organic treatments, with the ORG input/LOW crop diversity system being the most profitable (net returns=$234 ha−1yr−1and net present value=$1953 ha−1). Net returns averaged about 10% less for ORG/DAG compared to the most profitable system, and about 22% less for HIGH/DAG and RED/DAG (the best non-organic systems). The DAP treatments that included forage were not economically competitive with the other treatments, often producing economic losses. The relative profitability of the organic treatments was highly dependent on the existence of organic price premiums. When price premiums for organic crops were reduced to less than 70% of the 2007 levels, the organic treatments were less profitable than the comparable non-organic treatments. The organic treatments also experienced significantly lower (and often negative) net returns compared to the non-organic treatments during completion of the 3-year organic certification period. We estimated that it required 5–7 years after completion of certification for the organic treatments to break even with the comparable non-organic treatments. Thereafter the organic treatments produced consistently higher net earnings. Production costs averaged 16% lower with ORG management compared to the HIGH-input treatments, but we found little difference in total costs between the respective HIGH- and RED-input treatments. The organic treatments also displayed lower income variability than the non-organic treatments, with the ORG/LOW system being preferred by risk-averse producers, who do not subscribe to all-risk crop insurance, and with the ORG/LOW and ORG/DAG systems preferred by low and medium risk-averse producers when having the added financial protection from the Canada/Saskatchewan all-risk crop insurance program.

Effects of input management and crop diversity on non-renewable energy use efficiency of cropping systems in the Canadian Prairie

Although producers’ prime objective may be to increase net returns, many are also interested in conserving and enhancing the quality the soil, water and air resources through adopting more environmentally friendly production practices. This study compared non-renewable energy inputs, energy output, and energy use efficiency of nine dryland cropping systems comprised of a factorial combination of three methods of input management [high (HIGH), i.e., conventional tillage plus full recommended rates of fertilizer and pesticides; reduced (RED), i.e., conservation tillage plus reduced rates of fertilizer and pesticides; and organic (ORG), i.e., conventional tillage plus N-fixing legumes and non-chemical means of weed and pest control]; and three crop rotation systems with varying levels of cropping diversity [a fallow-based rotation with low crop diversity (LOW); a diversified rotation using annual cereal, oilseed and pulse grains (DAG); and a diversified rotation using annual grains and perennial forages (DAP)]. The study was conducted over the 1996–2007 period on a Dark Brown Chernozemic soil (Typic Boroll) in the Canadian Prairies. As expected, total direct plus indirect energy input was the highest for the HIGH and RED input treatments (3773 MJ ha −1 year −1), and 50% less for ORG management. Most of the energy savings came from the non-use of inorganic fertilizers and pesticides in the ORG management treatments. Further, total energy use was the highest for the DAG treatments (3572 MJ ha −1 year −1), and similar but about 18% lower for the DAP and LOW crop diversity treatments compared to DAG. Thus, overall, the HIGH/DAG and RED/DAG systems had the highest energy requirements (4409 MJ ha −1 year −1) and ORG/DAP had the lowest (1806 MJ ha −1 year −1). Energy output (calorimetric energy content) was typically the highest for the HIGH input treatments (26,541 MJ ha −1 year −1), was about 4% less with RED, and 37% less with ORG management. The latter reflected the lower crop yields obtained with organic management. Similarly, energy output was the highest for the DAP treatments (25,008 MJ ha −1 year −1), about 5% less for DAG, and 20% less for the LOW crop diversity treatments. The higher energy output with the DAP treatments largely reflected that the entire harvested biomass of the forage crops was included in energy output, while for grain crops only the seed was included. The straw and crop residues from annual crops were returned to the land to protect the soil from erosion and to maintain soil organic matter as this is the recommended practice in this semi-arid region. In contrast to energy output and to net energy produced, energy use efficiency (measured as yield of grain plus forage produced per unit of energy input or as energy output/energy input ratio) was the highest for the ORG input treatments (497 kg of harvested production GJ −1 of energy input, and an energy output/energy input ratio of 8.8). We obtained lower, but generally similar energy use efficiency for the HIGH and RED input treatments (392 kg GJ −1 and ratio of 7.1). Thus, overall, ORG/DAP was the most energy efficient cropping system, while RED/LOW and RED/DAG generally ranked the lowest in energy use efficiency. Our findings support the current movement of producers toward ORG management as a means of reducing the reliance on non-renewable energy inputs and improving overall energy use efficiency of their cropping systems. Our results also suggest that moving away from traditional monoculture cereal rotations that employ frequent summer fallowing, toward extended and diversified crop rotations that use reduced tillage methods, although resulting in an increase in energy output, will not significantly reduce the overall reliance on non-renewable energy inputs, nor enhance energy use efficiency, unless perennial legume forages and/or legume grain crops are included in the cropping mix.

Pasture Preconditioning Calves at a Higher Rate of Gain Improves Feedlot Health but Not Postweaning Profit

Over 2 yr, 132 calves (218 ± 12 kg initial BW) were used to compare a low- and high-input pasture preconditioning method to evaluate performance and profit during the preconditioning (weaning to 49 to 53 d) and finishing (end of preconditioning to slaughter) phases. At weaning (d 0), steers were randomly assigned to low-input or high-input treatments during preconditioning. Steers were fenceline-weaned for 7 d beginning on d 0 and were then transported to their respective pastures (d 7). The high-input steers had ad libitum access to a self-fed corn- and wheat middlings-based pellet, and low-input steers were supplemented with a 32% CP range cube delivered 3 times/wk to average 0.57 kg/d. At the end of preconditioning, high-input steers were 19 kg heavier (P < 0.01) and had a $20/steer greater final value (P < 0.01), but feed and total costs were $42/steer higher (P < 0.01). During preconditioning, low-input steers had a net income advantage of $20.54/steer (P < 0.01). After preconditioning, steers were finished at a commercial feedlot. During finishing, there were no differences in ADG, final BW, or carcass characteristics (P ≥ 0.28). Morbidity during finishing was 16.7 percentage units higher (P = 0.01) for low-input steers and resulted in a $6.63/steer greater (P = 0.05) medicine cost than for high-input steers. There was no impact (P = 0.49) on finishing net income or on profit from weaning to slaughter (P = 0.90). In conclusion, pasture preconditioning steers at a higher rate of BW gain can improve finishing health but may not increase postweaning profitability.

Impact of Different Management Technologies on the Production, Population Structure, and Economics of Freshwater Prawn Macrobrachium rosenbergii Culture in Temperate Climates

AbstractIn temperate zone ponds, maximization of total production without decreasing average harvest weight is of increased importance due to the relatively short growing season. Recent research on the freshwater prawn Macrobrachium rosenbergii has shown that techniques such as size grading juveniles and adding artificial substrate to the ponds can accomplish these goals, and their impacts appear to be cumulative. However, due to the greater investments required, private producers have been reluctant to adopt these practices. The studies involved in developing these independent technologies have been conducted over a number of growing seasons with their different environmental conditions. It is important that different production technologies being utilized by commercial producers be directly compared under standardized conditions. The objective of this study was to compare the previously recommended and widely used technology (39,200/ha; ungraded juveniles; no substrate) (Low Input) with an intensified version of that technology used by some producers (54,340/ha; ungraded juveniles; no substrate) (Medium Input) with a technology package developed through a series of research trials to maximize production (69,160/ha; graded juveniles; with substrate; phase feeding) (High Input) under standardized conditions. Each of the seven 0.04‐ha ponds were randomly assigned to either the Low Input, Medium Input, or High Input treatment with two, three, and two replicate ponds per treatment, respectively. Juvenile prawns (ungraded 0.6 ± 0.3 g; graded 0.9 ± 0.3 g) were stocked at one of the three densities according to its randomly assigned treatment. Low and Medium Input ponds received no added substrate while artificial substrate was added to the High Input ponds a rate sufficient to increase available surface area by 50%. Low and Medium Input Treatments were fed a 32% protein sinking pellet according to a feeding table. High Input ponds were fed at rates 20% above the feed table recommendations. After 104 d, survival was significantly higher (P± 0.05) in the High Input treatment (92%) than in the Medium Input treatment (83%), with Low Input ponds being intermediate (88%). Compared to the Low Input technology, the Medium Input technology significantly increased (P± 0.05) total production but significantly reduced average weight, so that Production Stock Index (PSI) and production of marketable size animals (&gt; 20 g) or premium size animals (&gt; 30 g) was not significantly increased (P &gt; 0.05). Compared to the original Low Input technology, the High Input treatment significantly increased (P &lt; 0.05) production (92%), average weight (6%), Production Stock Index (PSI) (102%), market‐able production (&gt; 20 g) (140%), production of premium size animals (&gt; 30 g) (130%), and feed efficiency (32%). The move from the Low Input technology to the High Input technology reduced breakeven costs by 13% based on operating costs and 22% based on total cost figures. In summary, adoption of the High Input technology appears to be biologically and economically justified if similar results can be obtained in commercial scale ponds.

Corn and Soil Fertility Responses to Crop Rotation with Low, Medium, or High Inputs

Corn (Zea mays L.) grown in annual rotation with soybean [Glycine max (L.) Merr.] has greater mineral nutrient accumulation and higher yields than corn grown in monoculture. This study was conducted to determine how crop rotation (continuous corn vs. corn rotated with soybean) with different input levels (tillage, herbicide, insecticide, and fertilizer rates varied to achieve high, intermediate, and low treatments) affected corn shoot dry weight, mineral nutrient (N, P, K, Ca, Mg, Cu, Fe, Mn, and Zn) composition at tasseling, pregrowing-season soil fertility (pH, organic matter, NO 3 - N, P, K, and total N), and grain yield on a Vienna loam (fine-loamy, mixed Udic Haploboroll) near Brookings, SD. Crop rotation increased total soil N and NO 3 - -N but decreased P when compared with continuous corn. The high input treatment resulted in higher soil NO 3 - -N levels than either the intermediate or low input treatments. Rotation with intermediate input increased corn shoot dry weight and P, K, and Ca accumulation compared with continuous corn with intermediate input. Grain yield responded differently to input levels within the two rotations. Corn yield following soybean was 32% greater than for continuous corn with intermediate inputs, but with high input levels there was no difference between rotation treatments. These results suggest that the level of inputs provided for corn can affect the crop rotation response.

Agronomic Responses of Winter Wheat Cultivars to Management Systems

Management of winter wheat (Triticum aestivum L.) should include N fertilization, crop protection, and seeding rates that allow efficient production based on cultivar and environmental yield potential. These studies were conducted to evaluate regionally grown cultivar responses to crop management systems in northern Idaho. In three environments, four cultivars were grown using management treatments (MT) similar to current recommended practices (MT3) ; a treatment with conservative N fertilization (MT2) ; a low input treatment with lower N, lower seeding rate, and minimal herbicide (MT1) ; and a high input treatment with higher N with split applications, plus a fungicide and growth regulator application (MT4). Data on grain yield, protein, test weight, plant height, and lodging were collected in all studies. In the two studies in 1992, leaf tissue N and soil N were analyzed and yield components were determined. Environment x MT and enviroment x cultivar interactions were found for grain yield, test weight, and protein. In 1991 at Moscow, the hard red wheat 'Weston' produced the highest grain yields across MTs and was the only cultivar to produce highest yields with MT4. Also in that environment, the three soft white cultivars produced higher yield and test weight and lower protein in MT2 than in MT3. In 1992 at Potlatch, limited soil water restricted yield, and MT1 had lower yields than other MTs, but protein content increased with higher N fertility. At Moscow in 1992, agronomic performance appears better in MT1 than in other treatments due to abundant early vegetative growth in the higher N fertility treatments that was followed by a soil water deficit throughout reproductive stages. Weston produced the lowest yield, heads per acre, and kernels per head at Moscow in 1992, but was highest in test weight, grain protein, and plant height. At both sites in 1992, yield components were positively correlated to yield, indicating treatment differences were influencing yield throughout several plant growth stages. High inputs (MT4) can be beneficial under some circumstances, but conservative N fertilization with conventional practices (MT2) gave the best overall agronomic performance across the tested environments and cultivars.

Increasing grain yield and water use of wheat in a rainfed Mediterranean type environment

Factorial experiments were conducted at eight sites in the central wheatbelt of Western Australia over two seasons. Time of sowing (mid-May, early June), cultivar (old tall, new semi-dwarf), nitrogen (N) fertilizer (- or +) and amount of seed sown (low and high) were combined as treatments, and grain yield, yield components, biomass, grain quality, water use, soil chemical and weather variables were measured. The aim was to increase grain yield by combining relevant agronomic inputs and increasing the seasonal water use or water use efficiency. Grain yields were increased by from 30 to over 100% by the combination of mid-May sowing, semi-dwarf cultivar, N fertilizer and increased seed level (high-inputs) compared to early June sowing, old tall cultivar, without N and lower seed level (low-inputs). The yield improvements mostly came from increased dry matter production at anthesis, largely due to increased applications of N and seed. Ear and kernel numbers were also increased by earlier sowing and N fertilizer and to a lesser extent by cultivar and increased weight of seed sown. Water use was increased at most sites, especially in the post-anthesis period and water use efficiency of grain production was increased at all sites. Soil evaporation was reduced by the high-input treatments and the low-input treatments did not use water supplies of &gt; 250 mm efficiently in grain production. It was concluded that appropriate combinations of cultivar and agronomic practices can increase grain yields linearly up to about 5 t ha-1 at seasonal water use of about 400 mm, even in situations where considerable water stress occurs during grain filling. Grain protein concentration was generally increased and hectolitre weight and small grain sievings were not adversely affected by increasing agronomic inputs.