Fresh green pea ( Pisum sativum L.) and winter wheat ( Triticum aestivum L.) are grown in rotation with intensive tillage in northeast Oregon. We evaluated simple yield models for both crops using data from a long-term experiment that included four tillage treatments and soil water content measurements. Yields were affected by tillage for some of the 21 yr of study, but there was no consistent ranking among tillage treatments from year to year and no effect when data were pooled. Standardizing pea yields to a tenderometer reading of 100 failed to improve detection of treatment effect. Tillage affected wheat water use (ET) for three of the study years and water use efficiency (WUE ET ) for one. Conservation tillage reduced pea ET for seven of the study years. For combined years, however, there was no tillage effect on yield, ET, or WUE ET of either crop. Wheat yield was better predicted from ET ( R 2 = 0.41) than by the Leggett model, which uses March soil water storage and spring rain ( R 2 = 0.12) Yield prediction was improved when ET was divided by seasonal mean daily water vapor pressure deficit (VPD) ( R 2 = 0.53) Multiple-regression equations using monthly rain predicted wheat yield well ( R 2 = 0.62) but coefficients differed among data sets. A model using monthly rain and heat degree day sum (HDDS) predicted pea yield much better ( R 2 = 0.65) than ET-based equations ( R 2 = 0.30)suggesting that pea yield is limited by factors other than water. For wheat, ET/VPD-based models should replace the Leggett model. However, for pea, multiple regression models predict yield better than ET-based models.

Winter wheat (Triticum aestivum L.) is grown in rotation with fresh pea (Pisum sativum L.) in the wetter (≥450 mm) zones of the inland Pacific Northwest, and with summer fallow in the drier (<450 mm) zones. Typically, this cropping system has been tillage‐intensive. Summer fallow deleteriously affects soil properties, while fresh pea markets have decreased for decades. Alternative wheat‐based cropping systems are needed. The objective of this 6‐yr study was to evaluate the agronomic viability of a winter wheat–dry pea rotation under four tillage systems. Primary tillage operations for wheat and pea residue, respectively, were: (i) fall disk and chisel plow (Fall D‐CH); (ii) fall moldboard plow and moldboard plow (Fall MBD‐MBD); (iii) spring moldboard plow and moldboard plow (Spring MBD‐MBD); and (iv) fall sweep and skew‐tread (Fall SWP‐SKW). Spring precipitation strongly influenced dry pea yield, but tillage had little to no effect. Pea yield could be predicted well by a model combining precipitation distribution with a heat stress index. Wheat yield was more influenced by winter than spring precipitation, and was ∼400 kg ha−1 less for the Fall SWP‐SKW treatment. Wheat protein content was also reduced in the Fall SWP‐SKW tillage treatment. The probable reason for lower wheat yield is poor weed control. Dry pea is agronomically viable as a rotation substitute for summer fallow or fresh pea. The apparent yield decline of wheat yield in the minimum tillage system needs to be evaluated in terms of tillage costs, and improved technologies for weed, residue, and N management.

Tillage systems that address soil conservation and sustainable crop yield need to be developed. Research was conducted on a Walla Walla silt loam (Typic Haploxeroll) to determine the long-term (19 years) effect of four tillage systems on soil properties and crop yield in a green pea (Pisum sativum L.)-winter wheat (Triticum aestivum L.) rotation that was started in 1968. The experimental design was a split plot with four replications. Wheat and peas were grown each season. The primary tillage systems were: (T1) fall moldboard plow after wheat and after peas (control); (T2) fall rototill after wheat and fall sweep after peas; (T3) spring moldboard plow after wheat and fall moldboard plow after peas; (T4) no tillage after wheat and fall sweep after peas. Soil measurements included bulk density, pH, organic carbon, penetration resistance, and saturated hydraulic conductivity. Profiles of bulk density, penetration resistance and pH revealed unique differences among treatments. However, there were no consistent differences in yield among the four tillage systems, in either green peas or wheat. From a crop production viewpoint, changes in soil properties on these tillage plots were inconsequential. From a soil erosion viewpoint, spring plowing (T3) and conservation tillage (T4) have an advantage over T2 and T1 because surface cover is maintained during the first winter following wheat harvest. Results show the importance of testing tillage systems over long periods of time and that the traditional system of fall moldboard plowing after wheat and after peas can be replaced by conservation systems without yield loss.

In some areas of the inland Pacific Northwest, surface runoff is a major source of water loss. Chiseling or plowing in the fall of the year, following wheat harvest, are farming practices to increase water infiltration especially in areas where frozen soil is anticipated. Water infiltration, overwinter water storage, and soil macroporosity were measured in fall tillage treatments of: (1) no tillage (NT); (2) chiseled stubble (C); (3) Paraplowed stubble (P). In spring, final infiltration rates for the respective treatments were 9.2, 22.8 and 23.5 mm h−1. Over winter, all treatments stored the same amount of water in the 3.35-m profile, however there were differences in the distribution of water in the profile. The fraction of macroporosity in a horizontal cross-section of soil, was different for each treatment and depth of cross-section. For the C treatment, macroporosity decreased from about 20% at the 7.6-cm depth to <1.0% at 25.4 cm, In contrast, macroporosity decreased with depth to a minimum of 6.9% at the 12.7-cm depth and increased to a maximum of 17.2% at 25.4 cm for the P treatment. NT had <1.0% macroporosity. Over winter soil settling is uncertain, however, water infiltration and macroporosity measurements conducted in March attest to the overwintering stability of the macropore structure of both C and P treatments.

Regression analysis was used to establish the effect of maximum daily temperatures on fresh pea (Pisum sativum L.) yield during the reproductive stage of growth. Maximum daily temperatures below 25.6C had little influence on pea yield. Temperatures above 25.6C depressed yield; this adverse effect increased exponentially as maximum daily temperature increased linearly. Predicted decrease in fresh pea yield ranged from 16 kg/ha per heat degree day above 27C to 67 kg/ha per heat degree day above 35C.

ABSTRACT: A four-year study was conducted at two historically wheat-fallow locations in Oregon to compare yields of annually cropped wheat in no-till, disk, and chisel tillage systems with yields of wheat following conventionally chiseled and rodweeded fallow. Tillage method did not affect yields of annually cropped wheat. This permits development of a management strategy that reduces soil erosion risk and increases average annual production. Annually cropped wheat, including two crops of lower yielding spring wheat, yielded 60% and 70% of winter wheat after fallow at the two locations. On a land use basis, annually cropped wheat, including the spring wheat crops, produced 138% of winter wheat after fallow.

Simple correlations between pea yields and October-through-March, April, May, and June precipitation were 0.52, –0.03, 0.22, and 0.44, respectively; the correlation between heat degree (above 25.6°C) day sum during blooming and pod filling with yield was –0.42. Multiple regression coefficients indicated that October-through-March, April, May, and June precipitation contributed 10, –3, 13, and 16 kg/ha per mm, respectively, to the yield. Each degree day above 25.6°C decreased the yield by 13 kg/ha. All coefficients except for April precipitation were highly significant. Approximately 65% of the year-to-year variation in pea yields was accounted for by these weather variables. Overwinter precipitation and excess heat each accounted for 27% of the pea yield variability. This model can be used to project pea yields based on the current moisture situation in this geographic area. Probabilistic description of weather information can be used along with this model to project probable pea yields.

AbstractSoil water content changes were supplemented with calculations of water flow between soil layers to provide an improved description of water uptake by dryland wheat (Triticum aestivum L.). This root‐sink description of water use, recognizing both measured change in water content and vertical redistribution (upward or downward) of water by flow between soil layers, is needed for a better understanding of plant‐soil and atmospheric factors involved in water stress when the wheat plant must rely on stored soil water for long periods. Water content changes were estimated from neutron meter measurements. Soil water flux was estimated from field measurements of both hydraulic conductivity and hydraulic head gradients; unsaturated conductivity beyond the range of field measurement was calculated with the pore interaction model of Marshall matched to field measured values at 250 mb. Seasonal water‐uptake patterns, determined by the root‐sink description, differed from those shown by only water content measurements. Peak water‐use rates did not coincide with maximum leaf area index, but coincided with the period from heading to completed head extension. Water flux in the profile was important for supplying water during grain filling and was critical in this layered soil, which restricted rooting to depths less than 150 cm.

Visual identification of S deficiency in white wheat is difficult since deficiency symptoms are nearly identical with those of N deficiency. In this study, S deficiency was best identified by determining the total N/S ratio rather than S concentration in vegetative tissue. Vegetative growth generally decreased from tillering to boot when the whole plant N/S ratio exceeded 17. The N/S ratio in S-sufficient plants declined gradually with age, implying that the critical N/S ratio may decline with advancing growth. Changes in stem: leaf ratio could have been responsible for the decline since the N/S ratio in stem tissue at heading was less than that of green leaf tissue.

AbstractA deterministic model of dryland winter wheat [Triticum aestivum ssp. vulgare (Vill., Host) ‘Nugaines’) growth in the Pacific Northwest was developed and field tested to more adequately quantify the influences of tillage induced microclimatic changes on wheat production. Daily dry matter accumulation of winter wheat is described by a modification of the Blackman compound interest formula. Daily environmental variables (soil water supply, N supply, soil and air temperature, relative humidity, wind, rainfall, and solar radiation) are used in the two‐component model. For inputs, initial conditions are needed which describe the field location (soil depth, water supply, fertilizer added, crop dry matter present, growth constants for the wheat variety, maximum rooting depth, and average temperature for the last 3 days). Dry matter production and the water budget are determined daily, until the water supply is exhausted or the crop is mature.Field tests of the model indicated accurate prediction of the effects of water and N supply and surface mulch for the first half of the growing season. After flowering, the observed dry matter accumulation was greater than projected by the water response function of the model. Much greater water use efficiency (daily increase in dry matter/ daily water transpired) occurred after flowering. This may be partially attributable to upward water flow from below 240 cm, which was not included in the measured available water. To improve growth prediction by the model, accurate measurement of the available water supply and alteration of the late season water response function are needed.

AbstractAlthough sulfur is routinely applied over much of the limited‐rainfall area of the northwestern United States, present diagnostic criteria for determining the need and frequency of S fertilization of white winter wheat [Triticum aestivum ssp. vulgare (Vill., Host) and T. aestivum ssp. compactum (Host)] are not highly successful. Our objective was to evaluate the initial and residual availability of applied S by investigating a) S uptake and distribution in wheat and b) the success of S concentration and N/S ratio as diagnostic criteria.Sulfur uptake, S concentration, and N/S ratios were compared with yield to measure S response over a period of 7 years after S application to a typical S‐deficient soil. Four rates of S (0, 17, 34, and 68 kg/ha) were applied as gypsum in factorial combination with four rates of N (0, 45, 90, and 180 kg/ha) as ammonium nitrate. Residual S effects were then evaluated in three subsequent wheat crops grown in a wheat‐pea (Pisum sativum L.) rotation with optimum N fertilization.Sulfur uptake and concentration in the first wheat crop was proportional to the rate of S applied, but accumulated primarily in vegetative tissue when present in excess of the amount required for grain protein. Uptake from residual S was much lower than uptake from the fertilizer application and S levels in grain were maintained at the expense of S in straw. Excellent residual availability of S (i.e., two wheat crops for a 17 kg/ha application) was attributed to the low amount of S needed for the additional grain yield (< 1 kg S/ha), recycling of substantial quantities of S in straw residues, and negligible leaching of S.The initial N fertilization significantly increased S uptake from the S source by increasing both S concentration and dry matter. Nitrogen applied without S increased dry matter but not S concentration. In contrast, S fertilization had little effect on N concentration in grain and straw and influenced N uptake only through its effect on dry matter production.Grain yield responses to S were poorly correlated with S concentration or N/S ratio in tissue because of the inconsistency of S accumulation in the plant‐parts and the dominating effect of N on yield. Decreased grain yield in wheat responding to S was associated with < 0.12% S in grain, <0.08% S in mature plants, and with N/S ratios > 16 in mature plants.

AbstractSulfur deficiency occurs in some soils in the northwestern United States. Wheat (Triticum aestivum L.) responses to S applications are highly variable and apparently related to N fertilization. Our objective was clarification of this variability by measuring yield responses of wheat (grain and straw) to S applied with a range of N (deficient to excess) for the first wheat crop and monitoring residual S effects on yields of three subsequent wheat crops.A factorial combination of four rates of S (0, 17, 34, and 68 kg S/ha) as gypsum and four rates of N (0, 45, 90, and 180 kg N/ha) as ammonium nitrate was applied to the first wheat crop at seeding. Wheat was grown in rotation with peas (Pisum sativum L.), wherein the peas were not fertilized and subsequent wheat crops received only a blanket application of N at the optimum rate (56 kg N/ha).First wheat crops after fertilization did not respond to S when N was deficient or optimum. Sulfur applied with excess N increased straw but not grain yield. Significant N to S interactions were noted. Residual S increased straw yield in all wheat crops and grain yield in 1 of 4 second, 3 of 3 third, and 2 of 2 fourth‐wheat crops. All S application rates gave similar yield increases in the second wheat crop. Residual S from 17 kg S/ha gave responses below maximum in the third wheat crop and residual S from 34 kg S/ha was marginally adequate in the fourth wheat crop.Wheat response to residual S was influenced by N rates applied to the first wheat crop. High N and S fertilization resulted in early drought and curtailed yields. Gradual release of residual S from recent organic matter apparently provided S at a rate adequate for efficient water use and maximum yield.

Abstract Maturity effects on yield of fresh peas ( Pisum sativum L.) were identified by yield-tenderometer measurements. A percent yield-tenderometer reading relationship was shown to be a useful means for yield adjustment to a common maturity—100 tenderometer reading. Analysis of random error in the predicted percent yield, as a function of tenderometer reading, indicates the need to plan harvests within the 90 to 110 tenderometer range. Alternatively, the yield-tenderometer reading relationships show the possible magnitude of errors incurred in comparing green pea yields when no adjustment is made for dissimilar tenderometer ratings.

AbstractHighly significant inverse yield‐protein relationships in wheat grain were found at each level of applied N in an irrigation‐N rate experiment on hard red winter wheat over a 3‐year period at North Platte, Nebraska. The chief effect of applied N with adequate water was to increase yields, while the chief or entire effect with severe water deficits was to increase protein content. In intermediate situations, N increased both yield and protein content.In dryland experiments in 1966 and 1967 showing significant grain yield response to applied N, protein content also increased. Where little or no yield response occurred, N mainly increased protein content. Content of NO3−N in the soil to a depth of 180 cm was also important in yield‐protein relationships.Average protein contents of about 20 hard red winter wheat varieties at different locations in Nebraska in 1966 and 1967 were also negatively related to grain yields. Protein contents varied more widely among locations than among varieties at each location.

SynopsisRoot development of winter wheat was studied in central Nebraska. Depth of soil moisture and rate of nitrogen fertilization were variables. A dense network of roots developed in soil when soil moisture tension was above 15 atmospheres. When moisture conditions were favorable, roots were observed at a depth of 13 feet. There was evidence of moisture depletion to a depth of 8 feet. Nitrogen fertilization increased root weights and moisture utilization at all moisture levels.

Several investigators (1, 2, 5, 10, 11, 13) have made use of plant analysis as an aid in diagnosing the nutrient requirement of plants and as a possible means of determining plant nutrient deficiencies in the soil. It has been shown as the of nutrients not in ample supply is increased, other factors being constant, plant growth is promoted and internal concentration of nutrient in the plant rises, at least in certain plant organs and at certain stages of development. Macy (6) has distinguished three portions of a curve relating yield to internal nutrient concentration. The section of the curve denoting minimum percentage'* shows a small increase in yield with constant internal concentration; the section of adjustment'' shows an increase in yield and internal concentration; and finally the section of consumption' * shows the yield remains constant with increasing internal concentration. Macy defines the transition between poverty adjustment and luxury consumption as the percentage. Ulrich (13) defines the critical nutrient of a plant as that narrow range of nutrient concentration in which the growth rate or yield of the plant first begins to decrease in comparison to plants at a higher nutrient This is determined by growing plants in media supplying two different amounts of the limiting nutrient, while other growth factors are held constant. At first there is no apparent difference in growth, but later the growth of the plants in the medium with the smaller amount of the nutrient under study is less than the growth of the plants in the medium with the larger amount of nutrient. The concentration of the nutrient under study in a suitable part of the plant harvested at this point of decreasing growth is a critical concentration or nutrient level. Although the nutrient level at this point varies for different species, it tends to be relatively constant for specific organs of the same plant, provided seasonal factors of light and temperature, and concentration of other ions in the nutrient medium do not inhibit normal plant growth. The red raspberry, Rubus idaeus L., is one of the important brambles grown in the state of Washington. Although the exact fertilizer requirements for this crop are not known, the use of mixed fertilizers is a general practice considered necessary for the production of high yields. The ? Published as Scientific Paper No. 861, Agricultural Experiment Stations, Institute of Agricultural Sciences, State College of Washington, Pullman, Washington. 617