205 research outputs found
Mid-Season P Fertilization Effects on Potatoes
Final potato tuber yields are a function of tuber growth rates and
the duration of the tuber growth period, particularly for the
indeterminate potato varieties. Nutrient uptake should be continuous
until the start of normal plant maturation since the tubers function as
major nutrient sinks during their growth. Nutrient uptake rates less
than those required for tuber growth will cause the mobile nutrients to
be translocated from the other plant parts to the tubers, eventually
causing a premature canopy senescence. Final tuber yields will be
reduced if this senescence starts when the environmental conditions are
still favorable for growth. Nutrient uptake rates can slow or stop
during the maturation growth stage since tuber growth during this period
mainly comes from the translocation of dry matter and nutrients from the
vegetative portions of the plant to the tubers
Indexes of Sulfur Deficiency in Alfalfa. I. Extractable Soil SO}4{-S
Sulfur deficiencies occur on many of the undeveloped
agricultural soils found in the mountain valleys of the
western United States; however, the majority of the S
soil-test correlation studies have been conducted on
leached and weathered soils. Identification of S deficiency
on alfalfa (Medicago sativa L.) growing in three
mountain valleys permitted the collection of S soil-test
correlation data for these undeveloped soils. This paper
reports the relationships found between extractable soil
SO?-S levels and the response of alfalfa to S fertilization.
Soil samples were taken from 13 experimental sites before
active plant growth commenced in the spring in 30-cm
depth increments to 92 cm. Soil SO?-S was extracted by
water, 0.1 M LiCl, and 0.032 M KH?PO? and measured
by the methylene-blue reduction method. Significant correlations
were obtained between the SO?-S extracted by
all three extractants from the 0- to 30-cm soil layers and
relative forage yields and total S uptake by the first harvest
of alfalfa at early bloom. Critical soil SO?-S levels
of 3.0, 3.0, and 4.0 ppm in this soil layer were found when
extracted by water, LiCl, and KH?PO?, respectively. Inclusion
of KH?PO?-extractable SO?-S to 92 cm did not
improve the curvilinear regression relationships, nor did
inclusion of percent soil organic matter. Increasing the
soil:extractant ratio from 1:2 to 1:3 did not significantly
change the amount of SO?-S extracted by the KH?PO?
solution. The 0.1 M LiCl solution is recommended for
extracting SO?-S from soils with relatively small amounts
of absorbed SO?-S
Indexes of Sulfur Deficiency in Alfalfa. II. Plant Analyses
Both soil and plant analysis are diagnostic tools used
in identifying S deficiencies; however, soil tests evaluating
soil S availability levels are not always successful and
deficiencies must then be identified by plant analysis.
In addition, the diagnostic tool must be correlated to crop
responses under various growing conditions to be useful.
Identification of S deficiency on alfalfa (Medicago sativa
L) in southern Idaho permitted the collection of correlation
data for both S soil tests and plant analyses. The
S soil test correlation data has been previously reported
(Aron. J. 66:578-581, 1974). This paper reports the relationships
found between the plant S indexes of total S,
SO?-S and total (N/S) ratio, and the response of alfalfa to
S fertilization. All data were evaluated by correlation
analyses.
The total S and SO?-S concentrations and the total
(N/S) ratio were all found to be satisfactory indexes of
S deficiency in whole alfalfa at early bloom. Maximum
forage yields were obtained when the tops contained
between 0.15 to 0.20% S or 0.05% SO?-S. Total S and
SO?-S were related and readily interchangeable as indexes.
Increases in total S above 0.14% S resulted from
the accumulation of SO?-S. Yield responses to S fertilization
were obtained when the total (N/S) ratio was greater
than 17 to 18. Total N and total S were not related, but
protein N increased linearly as protein S increased. The
protein (N/S) ratios were not constant and increased
from 17 to 23 as the degree of S deficiency increased
Lime effects on P availability
Nutrient uptake can be predicted by assuming that plant roots absorb
nutrients from the soil solution and that the rate of absorption is dependent
upon the nutrient concentration in the soil solution (2). The root growth
rate also affects P uptake since uptake is directly proportional to active
root surface area, particularly new root hairs. The three main soil
characteristics that describe the P supply to the plant root are: (a) P
concentration in the soil solution before growth, (b) the ability of the soil
to replenish the P in the soil solution, the buffer power, and (c) the P
diffusion rate through the soil. The diffusion process is the main supply
mechanism for P reaching the root surface.
There are several factors that directly or indirectly influence soil and
fertilizer P availability. These include soil, fertilizer, management, and
environmental characteristics. Additional details of the complex reactions
and interactions are beyond the scope of this paper, but can be found in
recent reviews (4, 7).
A nutrient survey showed that 25 out of 123 potato fields in Idaho had
soil test P concentrations (STPC) more than adequate, but petiole PO4-P
concentrations considered to be deficient (11). The significance of the
petiole PO4-P concentration in relation to plant growth needs have been better
defined (12) since that report. This paper presents data showing the effects
of lime on soil solution P concentrations and P uptake by plants
Plant analyses and interpretation
Plant analysis historic beginnings are generally attributed to T. de Saussure (1804)
following studies by van Helmont, Joseph Priestly, Henry Cavenish, and Antonine
Lavoisier. de Saussure showed that the composition of plant ash varied with the
part analyzed, with the age of the plant, and with the soil upon which the plant
grew. The ash was chiefly composed of alkalis and phosphates. Erasmus Darwin
in his 1800 book, Phytogia: The Philosophy of Agriculture and Gardening (London,
J. Johnson) wrote that both nitrogen (N) and phosphorus (P) were essential
components of plants. In 1833, the Fifth Duke of Richmond showed that the value
of bone meal fertilizing was due to its P component rather than calcium (Ca), although
Justus von Liebig (1852) is generally considered the father of soil fertility.
Readers interested in additional historic information should consult Ulrich (1948),
Bear (1948), and Russell (1976)
Lime effects on phosphorus availability in a calcareous soil
Crop yields are sometimes reduced on irrigated calcareous soils with
elevated lime concentrations. This study was conducted to determine
the influence of lime on P availability. The effects of acid-equivalent
lime concentrations and P fertilization rates on NaHCO3-soluble P,
anion resin-extractable P, P-adsorption isotherms in 0.01 M CaCl2,
and P uptake by sudangrass [Sorghum bicolor (L.) Moench] and potato
(Solanum tuberosum L.) were investigated in the greenhouse on
soil samples from the Portneuf silt loam (coarse-silty, mixed, mesic
Durixerollic Calciorthid). Plant P uptake was increased by P fertilization
and decreased by increasing lime concentration. Phosphorus
uptake was curvilinearly related to solution P (extracted by 0.01 M
CaCl2). Solution P concentrations increased linearly as the resin-extractable
P/equilibrium buffer capacity (EBC) ratio increased, where
EBC is the slope of the P-adsorption isotherm at the indigenous equilibrium
P concentration. The EBC increased as the lime concentration
increased. Phosphorus applications increased solution P and resin-extractable
P and decreased EBC within a given lime concentration.
These data indicate that the soil-test P concentration or P fertilization
rate should increase as the lime concentration increases to provide the
same degree of P availability and plant P uptake in this calcareous
soil
Nutritional requirements of potatoes
Plant nutrition is the practice of providing to the
plant the right nutrient, in the right amount, in the right
place, at the right time. This paper gives an overview of
the roles that each of the 16 essential nutrients have in
plant nutrition, their relative mobility as related to deficiency
symptom expression, and what is generally
known about nutrient responses to field applications on
potatoes (Solanum tuberosum L.) in the USA and
Canada. Maintaining high crop yields with minimum
nutrient losses to the environment is and will continue
to be a significant challenge to the potato producer.
Additional nutritional research efforts in genetically
modified plants, precision agriculture, food quality and
safety, fertilizer impurities, and other management concerns
should significantly help the producer in this
effort
Phosphorus Fertilization Economics
Fertilizer costs have become important factors in crop production in
recent years because of (a) increased energy costs associated with fertilizer
manufacturing and (b) material shortages. Since this trend will probably
continue, it is important that fertilization practices maximize economic returns
and fertilizer efficiencies. We have been evaluating the P fertilization
needs of some of'the major crops grown in southern Idaho since 1973.
This report compares the increased net crop value resulting from P fertilization
at different soil test P levels
Soil management practices
Soil management practices affect soil resources
obviously, but those practices also affect water
and air resources and the plants and animals that
depend upon those resources. Good soil management
builds soil quality, maintains or improves
water and air quality, and supports plant, animal,
and human life (NRCS, 1996a). Minimizing soil
erosion, increasing water infiltration, and promoting
biological activity through good management
ultimately produces a soil with physical and
chemical characteristics consistent with parent
material, topography, and climat
Measuring Soil Nitrogen Mineralization Under Field Conditions
The amount and rate of soil N mineralization are important
components that can be used to predict preplant
N fertilizer application and to evaluate the need for N
fertilization during crop growth. This study's purpose
was to evaluate the buried polyethylene bag technique
as a method for characterizing the N mineralized under
field conditions during the cropping season. Soil (Xerollic
Calciorthids) was placed in polyethylene bags and buried
in the 0 to 45 cm root zone of fallowed soils and where
corn (Zea mays L.) and potato (Solanum tuberosum 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 NO?-N concentrations in the buried polyethylene
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 temperature coefficient (Q??) of 2.3 between 10 C and 30 C. The relative
N mineralization rate was proportional to the soil water
content expressed as a percentage of the available water-holding
capacity. The N uptake by corn and potato crops
predicted from NO?-N changes in the rooting zone and in
the buried polyethylene bags resembled those measured
by plant sampling. The buried polyethylene bag technique
has potential for monitoring the soil N mineralization
process during the cropping season and for estimating
N uptake by crops. It also provides an alternative method
for estimating soil N availability for future crops and its
use should maximize N-fertilizer efficiencies
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