摘要:

Studies were conducted over a 5 year period on fine sandy loam soil to determine the importance of N mineralization rate on grapefruit (Citrus paradisi) production under subtropical conditions. Grapefruit trees grown on soils with mineralization rates greater than 0.47 ppm N/day produced near maximum yields during the first 3 years that young trees were in production but did not supply enough N after trees were large and fruit yields were above 16 MT/ha. Soil mineralizing 0.65 ppm N/day supplied enough N to produce 72% of the yield produced by trees fertilized with application of 148 kg N/ha.

ISSN:0010-3624    

DOI:10.1080/00103627709366729

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Depression of corn grain yields from nutrient stress has been studied extensively, but effects of nutrient stress on rates of corn development and yield determinants are less well understood. Nutritional effects on the number of kernels/unit area, growth rate/kernel, and duration of growth have implications concerning fertilization practices and yield potentials of crops. Two corn hybrids with equivalent silking dates but having different grain filling periods were grown in a field experiment. Fertility treatments consisted of a N series receiving 0, 112, or 336 kg of N/ha and a P‐K series receiving factorial combinations of 0, 22, or 112 kg of P/ha and 0, 56, or 224 kg of K/ha. Dates for grain initiation and maturity were determined for each plot along with tissue analyses of ear leaves, grain yields, and kernel weights. Concentrations of N and K in ear leaves generally corresponded to treatment levels of these nutrients, although Pioneer Hi‐bred 3390 appeared to be less efficient than Pioneer Hi‐bred 3334 in K uptake. Effects of nutrient stress on yield determinants depended on the determinant and nutrient under consideration. Severe N stress did not change length of grain filling periods, but decreased kernel numbers 30 to 70%. Stress for K, on the other hand, shortened grain filling periods about 13% and had only a slight effect on kernel number. Negligible P stress occurred in the experiment. The two hybrids produced equal quantities of grain/ha/day but the hybrid with a longer filling period (Pioneer 3334) filled many more kernels at a slightly slower rate and for a longer period of time to give a significantly greater grain yield compared to Pioneer 3390.

ISSN:0010-3624    

DOI:10.1080/00103627709366730

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Six of seven nonfertilized dryland crop rotations, consisting of combinations of fallow, wheat, alfalfa, and grass, have depleted several major plant nutrients in the soil in 20 years. The average contents of organic matter, total N, and exchangeable K were decreased by 14.5, 10.1, and 26.7%, respectively, in the 0‐ to 15‐cm soil horizon and by 24.1, 13.3, and 25.7% in the 15‐ to 30‐cm horizon. Total P content of the soils changed very little during 20 years of cropping. The amount of NaHC03‐extractable P decreased by 38.3% in the 0‐ to 15‐cm horizon of all soils except those in a manured fallow‐wheat‐wheat rotation, where a 30.6% increase occurred. Although soils were generally depleted, plant nutrients have not yet reached critically low levels, and therefore crop yields have been maintained at a fairly uniform level by using improved cereal varieties, timely tillage, good seedbed preparation, suitable seeding methods, and adequate in‐crop weed control. However, further depletion of plant nutrients from the soils will probably restrict crop production in the future. The results indicate that applications of adequate amounts of N, P, and K fertilizers, as determined by soil tests and correlative field tests, must be made to these and similar soils to ensure continued productivity.

ISSN:0010-3624    

DOI:10.1080/00103627709366731

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103627709366732

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Rapid digestion of plant tissue using sulfuric acid results in emission of large quantities of SO3fumes. These fumes are a serious hazard to personnel and cause corrosion of equipment and exhaust ducts. A simple apparatus was designed for effective fume control during plant tissue digestion with sulfuric acid using a heating block. The apparatus consists of a battery of reflux columns that can be installed as a unit on top of the digestion tubes after they have been placed in the heating block. The apparatus is very economical to construct.

ISSN:0010-3624    

DOI:10.1080/00103627709366733

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Drained golf greens, athletic fields, and various other turfgrass planting sites are frequently backfilled with specially‐prescribed coarse or very coarse‐textured root growth media to compensate for the effects of the shallow (20 to 50 cm deep), perched water table which forms at the drainage level. These areas are often planted with sod grown on much finer‐textured soils. This study examined the water retention in such nonhomogenous soil profiles following irrigation and drainage.

ISSN:0010-3624    

DOI:10.1080/00103627709366734

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

A procedure has been developed for multi‐element analysis of nitric‐perchloric tissue digests. Both plant and animal tissues appear to be quantitatively digested. The recommended procedure is rapid, requires a minimum of glassware manipulation and reagent addition.

ISSN:0010-3624    

DOI:10.1080/00103627709366735

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103627709366728

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor