Six greenhouse pot experiments were conducted in which yield and nutrient uptake responses of corn (Zea mays L.) or tall fescue (Festuca arundinacea Shreb) to N, P, K, lime, or temperature variables were measured. This paper describes yield—NO3‐N and total N concentration trends in these experiments. Crop concentrations of total N and NO3‐N during early growth increased consistently with amount of applied N. These concentrations usually decreased (by dilution and assimilation) with time of growth and yield response to other growth‐limiting nutrients and other factors. Concentrations of K also increased in corn with amount of applied K, and high K was associated with higher concentrations of NO3‐N during early growth in some experiments. This was usually true only for early crop growth periods during which rates of nutrient uptake exceeded growth rate. High K concentrations may have retarded growth and NO3‐N reduction and assimilation.

AbstractSlow‐release fertilizers should provide for more efficient nutrient use by the crop as well as reduce leaching losses. This study was conducted to measure crop response to N or K in uncoated urea, ammonium nitrate (AN), S‐coated urea (SCU), KCl, and S‐coated KCl (SCK) and to relate leaching losses to NO3‐Nan and cations. In one series, granular N sources to supply 200 or 400 kg of N/surface ha were mixed with the upper 20 cm of a 1:1 mixture of Norfolk s1 (Typic Paleudult) and builders sand contained in 15‐ ✕ 120‐cm columns. A second series was similarly fertilized with K sources to supply 100 or 200 kg of K/surface ha.Soil columns were left fallow or planted to tall fescue (Festuca arundinacea Shreb. ‘Kentucky 31’) which was harvested six times at 4‐week intervals. Following the sixth harvest of fescue, stubble and roots were incorporated into the soil along with a second application of N or K and cultures were planted to sorghum‐sudangrass (Sorghum bicolor ✕ Moench Sorghum vulgare sudanense ‘Green M’), which was harevsted four times at 4‐week intervals. Water was applied as required for crop growth and once during each growth period all columns (including fallow) were heavily watered to collect liters (10 cm) of leachate from each.Total recovery of N by both crops was in the order: SCU‐12 > split‐AN > SCU‐20 > urea > AN > no N. With cropping, 0 to 11% of applied N was found in drainage water. Under fallow, losses of N were much higher (29 to 72%) and were in the order: split‐AN > SCU‐12 = SCU‐20 > AN = urea > no N. These results support the premise that slow‐release fertilizers supply more N for crop response, but may not reduce leaching losses. Leaching of cations was well correlated with loss of NO3‐N (r = 0.83 to 0.90) under fallow, but was less correlated (r = 0.33 to 0.74) under grass.Recovery of K by both crops was near 100%. Applied K decreased loss of NO3‐N, Ca, and Mg under cropping and increased losses under fallow. Leaching of NO3‐N and cations was highly correlated. Applied N and oxidation of S in S‐coated products both contributed to acidification of the soil, which intensified leaching of Ca and Mg.

Pot experiments were conducted to determine effects of applied N on NO3‐N and total N concentrations in Swiss chard (Beta vulgaris var. cicla) and of applied N, P, and K on Bloomsdale spinach (Spinacia oleracea L.) and on curly mustard (Brassica pervirdis L.). Ammonium nitrate produced greater increases in NO3‐N and total N concentrations in chard than did sulfur‐coated urea at the same rates of applied N. Both N and K increased yields and NO3‐N accumulation in spinach and mustard; response to applied P resulted only in decreased NO3‐N. Both total and NO3‐N concentrations decreased with dilution and/or assimilation associated with time of growth and higher yields. An examination of published results with several spinach cultivars indicates that differences in NO3‐N accumulation attributed to leaf type can also be explained by the higher yields of the low NO3‐N accumulators. The same is true for differences in NO3‐N accumulations attributed to light and temperature effects.

AbstractWidely varying results and conclusions are reported in the literature concerning the effects of environmental growth factors, especially temperature, on yields of dry matter and nutrient absorption by plants. The purpose of this paper is thus to evaluate the effects of temperature in three greenhouse pot experiments and as reported in the literature on yield‐nutrient uptake relationships. Several rates of applied N and P were compared in Exp. 1 for oats (Avena sativa L.) grown for 7 weeks at three combinations of day length and temperature. Several rates of N and P in factorial combination were compared in Exp. 2 for corn (Zea mays L.) grown for 4 weeks at water bath temperatures of 16 and 27 C. Corn was also grown in Exp. 3 for 3 and 6 weeks to compare P rates and temperatures of 16 and 21 C and at ambient temperatures (25 to 35 C). Dry matter yields and uptake of N and P (also of cations in Exp. 3) were determined. Plant nutrient concentrations, especially of P, increase with higher soil temperatures in experiments of short duration and with little yield response to temperature. However, with marked yield response, dilution of plant nutrient concentrations but higher uptake are the dominant trends with increase in temperature up to the optimum for each crop species. The reverse usually occurs at temperatures above the optimum. Release of nutrients from the substrate with higher temperatures varies greatly with soil fertility level and amounts of applied nutrients. Rate of root growth is also very likely a predominant factor in plant uptake of nutrients, especially those having limited mobility in the soil.

AbstractHybrid corn (Zea mays L.) was grown in infertile soil fertilized with none and three nonzero rates of N, P, or K in separate treatment series; other nutrients were applied in each series at uniform levels. Near‐linear increases in uptake of N, P, or K with amount applied occurred during 25, 41, and 53 days' growth. Concentrations of N, P, or K increased with amount applied and decreased with continued growth in each series; uniformly applied P and K, N and K, or N and P were diluted with increase in dry matter resulting from continued growth and yield response to increasing amounts of the third nutrient. Yield‐concentration relationships in the N response series were similar for N, Ca, Mg, Mn, and Zn. Response to P or K resulted in dilution of all other nutrients. Concentrations of total cations increased with concentrations of N in each response series; the reverse was true with P and K. Thus, the results suggest that a positive relationship between dry matter yields and total cations (C), total inorganic anions (A), and C‐A depends on whether yield response is due to N or to other growth‐limiting factors.

AbstractPot experiments were conducted in a greenhouse to study nutrition of rice (Oryza sativa L., cv. Nato) under flooding and upland conditions. Yields of rice grown in one experiment on Mountview silt loam increased rectilinearly with 0‐, 400‐, and 800‐mg rates of N/pot (5 kg of soil). Concentrations of N in grain + straw at maturity were uniformly low. Yields with the various water regimes were in the order: no flooding < flooding after 10 weeks < flooding after 6 weeks < flooding after 3 weeks. Multiple rates of N from 250 to 2,000 mg/pot and P from 0 to 1,000 mg/pot (6.25 kg of soil) were applied for Nato rice grown on Mountview silt loam and Sango silty clay loam in a second experiment. Marked yield responses to N and P were obtained. Yields of straw and of grain + straw, N uptake, and N recovery were higher on nonflooded than on flooded soils. Grain yields, however, were slightly higher with flooding.Uptake of N, P, Ca, Mg, Mn, and Zn increased with yield response to N and P, while K uptake decreased on the Mountview soil. Concentrations of N and P increased with applied N and P, respectively, while concentrations of other nutrients were diluted in most situations with yield response to N or P on both flooded and nonflooded soils.These results indicate that with adequate applied nutrients, especially N, yields of rice with adequate water but without flooding can equal or even exceed those under flooding.

Dry matter‐N and S concentration relationships and N/S ratios were studied in corn ( Zea mays L.) grown in several greenhouse pot experiments on soil deficient in both N and S for good growth. Such relationships and ratios are basic to the proper interpretation of plant analysis results. Minimum concentrations in the dry forage necessary for continued growth of corn at 6 to 8 weeks were about 0.70% N and 0.045% S. Total N/S ratios varied widely from this ratio of 16, depending on age of plant, excess of N or S necessary for growth, and as a result of dilution of one nutrient by growth response to the other. This value of 16 at the minimum N and S concentrations approximates the ratio in plant proteins. Variations from the ratio of 16 indicate varying amounts of labile, nonprotein N or S.

AbstractTriammonium pyrophosphate [(NH4)3HP2O7] was found to be less effective than monoammonium orthophosphate [NH4H2PO4] when both were freshly added as sources of P for corn (Zea mays L.) grown in cool soil (16C). No difference in effectiveness was found between these sources when freshly applied to warm soil (24C). Incubation prior to planting reduced the effectiveness of both sources, particularly when the soil was warm during the incubation period.