摘要:

A three year‐old ‘Arapaho’ blackberry planting at the University of Arkansas Fruit Substation was used for a nitrogen (N) study. Treatments, which began in 1994 and continued through 1996, were: 1) control—no N applied, 2) 56 kg ha‐1N applied in a single application in early spring, 3) 112 kg ha‐1N applied in a single application in early spring, and 4) 112 kg ha‐1N applied in a split application with one‐half applied in the early spring and one‐half applied immediately after harvest. Fruit was harvested from the plots in June and total yield and average berry mass were determined. Foliar samples were collected in August and elemental analysis conducted. Primocanes in each plot were counted at the end of the growing season. Over the three years, there was no significant treatment effect on yield, berry mass, or primocane number. A trend toward higher primocane number with N application was seen, however. Foliar elemental content of N, phosphorus (P), potassium (K), calcium (Ca), sulfur (S), and manganese (Mn) were affected by either N dose or time of application. Foliar N content was highest for the split application but no other benefit was found from that practice. Calcium was higher when no N was applied, Mn was greater at higher N rates, and the control had the lowest foliar N level each year. No effect from N treatment was found for leaf chlorophyll content or stem and bud cold hardiness.

ISSN:0010-3624    

DOI:10.1080/00103629809370152

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Different plant analysis methods including varied incubation times with 0.5N and IN hydrochloric acid (HCl), diacid [nitric (HNO3) and perchloric (HClO4) acids], triacid [HNO3, sulfuric acid (H2SO4) and HClO4], H2SO4+hydrogen peroxide (H2O2) (Wolf method), and 0.5N and lN ammonium acetate (NH4OAc) were evaluated for measuring the potassium (K) concentration in straw and grain samples of cereal, legumes, oilseed crops, and fruit‐tree leaves. The average K concentration in nine plant materials indicated that K extracted by 0.5N and lN HCl for 5 minutes, 1 hour, and 17 hours contact periods did not differ significantly. But the amount of K extracted by these acidic solutions gradually decreased during incubation, possibly due to reabsorption of released K by the plant material. The amount of K released in to the 0.5N HCl and IN HCl extractants was in close agreement with that obtained with the standard triacid method. The IN NH4OAc extraction method slightly overestimated the K concentration in the materials compared to the other methods. Differences were observed among the methods in extracting K from different plant materials. In case of grain samples, the triacid method gave slightly higher values than that obtained by IN NH4OAc extraction. The results suggest that the 0.5N HCl and lN NH4OAc extraction methods can be used for the determination of K in plant tissues as these methods gave lower standard deviation and coefficient of variation values compared to the triacid method.

ISSN:0010-3624    

DOI:10.1080/00103629809370153

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Three growing media consisting ofSphagnumpeat mixed with either a siliceous sand, a sandy soil or a fen peat, were studied in relation to the effect of indolebutyric acid (IBA), applied at 2.0 g I‐1as a 10 s root dip, on the growth of containerized ‘Carrizo’ citrange seedlings. Plants grown in the fen peat mixture showed the highest root development and vegetative growth, but were insensitive to IBA. This auxin improved the growth of plants grown in both sand‐and soil‐based mixes. Similar trends were observed for nitrogen (N) and phosphorus (P) foliar concentrations, but potassium (K) concentrations in leaves were only increased in plants grown in the soil‐based growing medium.

ISSN:0010-3624    

DOI:10.1080/00103629809370154

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Optimum crop production depends, among other things, on the maintenance of adequate plant nutrients in the root zone. The objective of this study was to find a reliable index for assessing needs for supplemental phosphorus (P) in soils of Morogoro District, Tanzania. Six indices of P availability, namely: Bray and Kurtz No. 1 (BK1), Bray and KurtzNo.2 (BK2), Mehlich 1, Mehlich 3, Olsen and ammonium bicarbonate‐DTPA (AB‐DTPA), were evaluated. Evaluation of the P indices involved relating extractable P contents by different methods with crop response data expressed as relative yields. The response data was obtained from pot trials with soil samples from ten repesentative soils designated as benchmark soils of the district. Treatments were absolute control, 0, 10, 20, and 30 mg P kg‐1of soil. Correlation of maize relative yields with soil test values by the six indices of P availability resulted in correlation coefficients ranging from 0.65 to 0.90. The Olsen method gave the highest r value suggesting that it was superior to the others. However, using the Cate and Nelson approach, the Olsen and ammonium bicarbonate‐DTPA methods were found to be atparand superior to the others. They each accounted for 76% of the variations observed in maize relative yields, respectively. The critical P levels for the indices were 10.50 mg P kg‐1for Olsen and 2.80 mg P kg‐1for the AB‐DTPA method. Phosphorus fertility categories were delineated in relation to Olsen extractable P as: low (<6.50 mg P kg‐1), medium (6.50 to 23.0 mg P kg‐1), and high (>23.0 mg P kg‐1). Based on this classification it was determined that 16%, 25 %, and 59% of the surveyed area had low, medium, and high P levels, respectively. About 40% of the surveyed area may, therefore, require fertilization with P for optimum yields.

ISSN:0010-3624    

DOI:10.1080/00103629809370155

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Studies were conducted on some soils of Morogoro District to estimate economically optimum phosphorus (P) fertilizer recommendations for maize from soil tests. The studies involved the estimation of maize yield response to added P in pot and field experiments. Maize responded to added P at three sites. At all three sites, the residual effects of added P lasted up to three years suggesting that added P was not strongly fixed in these soils. Yield responses were related to extractable P contents by the Olsen and AB‐DTPA methods through a modification of the Mitscherlich‐Bray equation. Estimated model parameters were incorporated in equations for estimating optimum P fertilizer rates for different cost‐price ratios (p) and marginal rates of return (R). At the p and R values that prevailed in the study area during 1997, recommended P fertilizer rates (PR) could be determined by the equation: PR=68.497–1.191T (Olsen P). Calculated P fertilizer rates for P deficient sites in the district ranged from 15 to 60 kg P ha‐1. This wide range underscored the importance of site specific fertilizer recommendations.

ISSN:0010-3624    

DOI:10.1080/00103629809370156

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103629809370131

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor