The amount and rate of soil N mineralization are important components that can be used to predin ct ecpregant N fertilizer application and to evaluate the d N fertilization during crop epowth. This study's was to evaluate the burl d polyethylene bag as a method, for characterizing the N mineralized field conditions during the cropping season. Soil (Xerollit Calciorthids) was placed in polyethylene bags and buried in the 0 to 45 an root zone of followed roils and where corn (Tea mays L) and potato (Solanunt taberonan L.) were being grown. The NO,-N content of the soil in the bags was compared with that in the root zone at selected time intervals (10 to 14 days) from April to October.The soil NOrN concentrations in the buried polynhylate bags were similar to those in irrigated fallow soils from April to October after correction for different soil water contents. The N-mineralization rate between sampling . intervals had an average ten tune coeffi.

Seed yields of Phaseolus vulgaris L. have not increased under the current production systems even with more precise management inputs. Recent studies of snap beans grown for processing suggested that yields could be increased by high density planting. Our study was made to evaluate the effects of plant populations on the seed yields of four representative field and snap bean cultivars grown under sprinkler irrigation on a Portneuf silt loam (Xerollic Calciorthid).Two cultivars each of bush snap beans and semivining field beans were grown in plant populations of 107,600 to 968,700 plants/ha in nearly equidistant plant arrangements. The optimum plant population or seed yield for the bush cultivars was approximately 400,000 plants/ ha and less than 300,000 plants/ha for the semivining cultivars. At smaller plant populations, seed yields decreased for the bush cultivars and remained constant for the semivining cultivars. The harvest index (seed weight/ total plant weight) increased slightly for the bush cultivars as their plant population decreased, but remained constant for the semivining cultivars up to 300,000 plants/ ha, then increased rapidly. The production index (seed yield/amount seeded) increased curvilinearly as plant population decreased for all cultivars. Plant maturity was advanced 7 to 10 days at the highest plant populations for all cultivars. Pods were located at upper nodes on the plants as the populations increased. These results suggest that greater seed yields could be expected with the equidistant plant arrangements as compared with conventional row plantings for the bush cultivars, but not for the semivining cultivars, primarily because of the ability of the semivining cultivars to compensate for the increased area/plant at smaller plant populations. Additional index words: DRY edible field and snap bean (Phaseolus vulgaris L.) cultivars grown for seed under furrow irrigation are presently planted in row widths of 50 to 60-cm and spaced 5 to 7 cm apart within the row for maximum yields (9, 13). Under this production system, improving soil fertility levels and other management practices has not always increased bean seed yields.The practice of using herbicides for weed control, increased sprinkler irrigation, greater flexibility in the harvesting methods, and the release of erect, higher pod setting cultivars has renewed interest in solid stand plantings as one way of increasing seed yields. Planting the rows closer, while simultaneously varying the within-row spacing, so that the plants are arranged more equidistantly, has been shown to increase seed yields (2, 4). Studies with snap beans for processing showed that pod yields could be increased up to 64% by planting in 30-cm rows as compared to 91-cm rows (5). Pod yields were highest for plants planted in a square (12.7 x 12.7-cm to 15.2 )< 15. cm), with the optimum plant spacing depending upon the cultivar (11). Larger percentages of smaller pods were found in the closer plant spacings, however this may have been due to pod maturity d...

Knowledge of the effect of plant populations on the seed yield components of beans (Phaseolus vulgaris L.) is needed to design management systems utilising the genetic potential of different cultivars and to aid in the development of higher seed-yielding cultivars. The objectives of this study were to evaluate (a) the effect of different plant populations (area/plant) on the seed yield components as related to seed yield/plant, and (b) the relative differences between determinate ('Canyon', and 'Blue Lakes 274') and indeterminate ('UI.114', and 'Big Bend') bean cultivars. Seed yield/plant and the seed yield components were measured on plant populations from 1117,600 to 968,700 plants/ha (100 to 930 cm'/plant) grown in a systematic design. Data were evaluated by path coefficient analysis based on correlations calculated from logarithmically transformed data. Pods/plants increased linearly as area/plant increased (decreasing plant population) for all cultivars studied, and had the largest effect on seed yield/plant. Seeds/pod and g/seed also increased as area/plant increased for the indeterminate cultivars, but remained relatively constant for the determinate cultivars. As a result, the seed yield/area is relatively constant over a wide range of plant populations for the indeterminate cultivars, but decreases at the smaller plant populations for the determinate cultivars. It also indicates that the determinate cultivar is subject to less competitive stress than the indeterminate one at the higher plant populations. The greatest potential for seed yield increases in high plant populations is with determinate cultivars.

Conservation tillage practices can significantly reduce soil erosion, improve water distribution, and decrease environmental concerns in furrow-irrigated fields. Developing fertilizer management practices that optimize crop yields after legumes in these systems will aid their adoption. This study evaluated the N fertilizer requirement of wheat planted in herbicide-killed alfalfa stubble.The N available after legumes is sufficient for maximum crop yields in many cropping systems. Fertilizing without accounting for the "extra" N mineralized from legume residues can contribute to high nitrate-N concentrations in the soil during crop production and increase nitrate-N leaching potential. Tillage practices also affect the physical, biological, and chemical nature of the soil, changing the N mineralization rates and N fertilizer requirements.Two soft white winter wheat (var. Stephens) experiments and one hard red spring wheat (var. Bronze Chief) experiment were conducted in southern Idaho between 1984 and 1987 on a furrow-irrigated silt loam soil. The wheat was no-till planted with a conventional double disk opener drill into alfalfa stubble, killed by spraying the fall regrowth with a mixture of 1 qt glyphosphate and 2 qt 2,4-D. Nitrogen fertilizer (ammonium nitrate) was surface broadcast in the spring at rates between 0 and 200 or 240 lb/acre. Does wheat no-till planted in herbicide-killed alfalfa stubble require N fertilization for maximum grain yields?Nitrogen fertilization increased grain yields in all three field experiments ( Table 1). The N fertilizer response occurred because sufficient N had not mineralized from soil and legume sources before the wheat plant started rapid N uptake (Fig. 1). Nitrogen uptake rates by the wheat between jointing and soft dough growth stages were approximately twofold larger than soil N mineralization rates. This rapidly depleted the available nitrate-N in the rooting zone when fertilizer N was not applied. About 109 lb N/acre were taken up by the wheat plants at soft dough growth stage from soil and legume residue sources. The apparent N fertilizer recovery was 76%.In general, we recommend that other crops be planted in the herbicide killed alfalfa stubble instead of cereals if early spring leaching is not a problem. The N uptake patterns of potato, corn, and sugarbeet are substantially later than wheat's (Fig. I). This allows more nitrate-N to accumulate in the root zone from mineralization before crop N uptake starts and uses more of the N mineralized in late summer and early fall, reducing the potential for subsequent nitrate-N leaching.