NPK Soil Research Articles

Impact of drip fertigation on productivity of arecanut ( Areca catechu L.)

The present investigation was conducted at Vittal, Karnataka, India during December 1996 to May 2006 to evaluate the effect of four fertigation levels (25, 50, 75 and 100% of recommended fertilizer dose, 100:18:117 g N:P:K palm −1 year −1), three frequencies of fertigation (10, 20 and 30 days) and two controls (control 1, i.e., drip irrigation without fertilizer application and control 2, i.e., drip with 100% NPK soil application) on productivity and resource use efficiency of arecanut. The experiment was laid out in RBD incorporating factorial component (4 × 3 + 2) in 2-year-old arecanut plantation. Pooled analysis of 4-year data indicated the significant influence of both fertilizer dose and frequency of fertigation on kernel yield of arecanut. Among fertigation levels, the kernel yield was significantly higher in 75% NPK fertigation, i.e., 75:13.5:87.7 g N, P, K application per year (3721 kg ha −1) than in other levels (3083–3121 kg ha −1). The yields observed in 10 (3431 kg ha −1) and 20 days frequencies (3382 kg ha −1) were at par and significantly superior to monthly fertigation frequency (2952 kg ha −1). Fertigation of 75% NPK at 10 days frequency registered maximum yield (4017 kg ha −1), which was closely followed by fertigation of 75% NPK at 20 days frequency (3924 kg ha −1) and fertigation of 100% NPK at 20 days frequency (3579 kg ha −1). The yield increase with 75% NPK fertigated at 10 days interval was 100% over control 1 (2008 kg ha −1). Different fertigation levels registered higher dry matter partitioning to kernel, i.e., 6.7–7.4% of the total biomass than no fertilizer application (5.6%). A significant correlation between biomass accumulation in different parts and fertigation levels indicates the importance of efficient application of nutrients at correct time and quantity. Leaf water potential increased significantly with increase in frequency of fertigation from 10 to 30 days interval. A strong linear correlation ( R 2 = 0.914) was observed between fertigation level and total root biomass. The root biomass increased considerably from 3.23 (no fertilizer) to 7.99 kg per palm (75% NPK). Significant relation between root biomass and organic carbon content in soil based on polynomial regression ( R 2 = 0.769) was also noticed. Water use efficiency (WUE) was significantly superior at 75% NPK applied at 10 days interval over 100% NPK applied at same interval. However, it was at par with 75 and 100% NPK applied at 20 days interval Agronomic nutrient use efficiency (ANUE) was significantly higher at 25% NPK (14.9 kg kernel produced per kg nutrient applied). Fertigation up to 75% NPK provided a higher ANUE than the combination of drip irrigation and soil application of 100% NPK indicating greater production at lesser application rates. The 11-year study indicated that adoption of fertigation not only increases productivity, but also ensures higher efficiency of the two most critical inputs, i.e., water and nutrients in crop production.

Effects of long-term amendment of organic manure and nitrogen fertilizer on nitrous oxide emission in a sandy loam soil

To understand the effects of long-term amendment of organic manure and N fertilizer on N 2O emission in the North China Plain, a laboratory incubation at different temperatures and soil moistures were carried out using soils treated with organic manure (OM), half organic manure plus half fertilizer N (HOM), fertilizer NPK (NPK), fertilizer NP (NP), fertilizer NK (NK), fertilizer PK (NK) and control (CK) since 1989. Cumulative N 2O emission in OM soil during the 17 d incubation period was slightly higher than in NPK soil under optimum nitrification conditions (25°C and 60% water-filled pore space, WFPS), but more than twice under the optimum denitrification conditions (35°C and 90% WFPS). N 2O produced by denitrification was 2.1–2.3 times greater than that by nitrification in OM and HOM soils, but only 1.5 times greater in NPK and NP soils. These results-implied that the long-term amendment of organic manure could significantly increase the N 2O emission via denitrification in OM soil as compared to NPK soil. This is quite different from field measurement between OM soil and NPK soil. Substantial inhibition of the formation of anaerobic environment for denitrification in field might result in no marked difference in N 2O emission between OM and NPK soils. This is due in part to more rapid oxygen diffusion in coarse textured soils than consumption by aerobic microbes until WFPS was 75% and to low easily decomposed organic C of organic manure. This finding suggested that addition of organic manure in the tested sandy loam might be a good management option since it seldom caused a burst of N 2O emission but sequestered atmospheric C and maintained efficiently applied N in soil.

CO 2 emission in an intensively cultivated loam as affected by long-term application of organic manure and nitrogen fertilizer

A long-term field experiment was conducted to examine the influence of mineral fertilizer and organic manure on the equilibrium dynamics of soil organic C in an intensively cultivated fluvo-aquic soil in the Fengqiu State Key Agro-Ecological Experimental Station (Fengqiu county, Henan province, China) since September 1989. Soil CO 2 flux was measured during the maize and wheat growing seasons in 2002–2003 and 2004 to evaluate the response of soil respiration to additions and/or alterations in mineral fertilizer, organic manure and various environmental factors. The study included seven treatments: organic manure (OM), half-organic manure plus half-fertilizer N (NOM), fertilizer NPK (NPK), fertilizer NP (NP), fertilizer NK (NK), fertilizer PK (PK) and control (CK). Organic C in soil and the soil heavy fraction (organo-mineral complex) was increased from 4.47 to 8.61 mg C g −1 and from 3.32 to 5.68 mg C g −1, respectively, after the 13 yr application of organic manure. In contrast, organic C and the soil heavy fraction increased in NPK soil to only 5.41 and 4.38 mg C g −1, respectively. In the CK treatment, these parameters actually decreased from the initial C concentrations (4.47 and 3.32 mg C g −1) to 3.77 and 3.11 mg C g −1, respectively. Therefore, organic manure efficiently elevated soil organic C. However, only 66% of the increased soil organic C was combined with clay minerals in the OM treatment. Cumulative soil CO 2 emissions from inter-row soil in the OM and NPK treatments were 228 and 188 g C m −2 during the 2002 maize growing season, 132 and 123 g C m −2 during the 2002/2003 wheat growing season, and 401 and 346 g C m −2 yr −1 in 2002–2003, respectively. However, during the 2004 maize growing season, cumulative soil CO 2 emissions were as high as 617 and 556 g C m −2, respectively, due to the contribution of rhizosphere respiration. The addition of organic manure contributed to a 16% increase in soil CO 2 emission in 2002–2003 (compared to NPK), where only 27%, 36% and 24% of applied organic C was released as CO 2 during the 2002 and 2004 maize growing seasons and in 2002–2003, respectively. During the 2002/2003 wheat growing season, soil CO 2 flux was significantly affected by soil temperature below 20 °C, but by soil moisture (WFPS) during the 2004 maize growing season at soil temperatures above 18 °C. Optimum soil WFPS for soil CO 2 flux was approximately 70%. When WFPS was below 50%, it no longer had a significant impact on soil CO 2 flux during the 2002 maize growing season. This study indicates the application of organic manure composted with wheat straw may be a preferred strategy for increasing soil organic C and sequestering C in soil.

Microbial biomass dynamics in recently air-dried and rewetted soils compared to others stored air-dry for up to 103 years

Our aim was to compare the soil microbial biomass concentration and its activity (measured as CO 2–C evolved) following the rewetting and aerobic incubation of soils which have previously been stored air-dry for different periods. Some of the soils have been stored in the Rothamsted sample archive for 103 years, others were comparable freshly sampled soils following air-drying and rewetting and other soils were stored air-dry for 2 years then rewetted for the work described here. Following air-drying, soil ATP concentrations were variable in recently air-dried soil, comprising about 10–35% of the initial ATP concentrations in fresh soil. Following rewetting, the percentage recovery of ATP increased in all soils by 7 days, then declined to between 73% and 87% of the original ATP concentration in the air-dried soils by day 12. Storage of air-dried soils decreased the ability of the microbial biomass to restore its ATP concentrations. For example, the ATP concentration in a soil sampled from stubbed (i.e. tree seedling, saplings and bushes cut frequently to ground level) grassland of the Broadbalk continuous wheat experiment at Rothamsted then air-dried for 2 years was only about 14% of that in the fresh soil at 2 days after rewetting. In other soils from the Hoosfield Barley Experiment, also at Rothamsted, previously given NPK or FYM since 1852, and sampled then stored air-dry for between 13 and 83 years, from 52% to 57% of the ATP in the comparable fresh soils was measured at two days after rewetting. The soil ATP concentration then changed little more up to 12 days. One of the most interesting findings was that while the microbial biomass ATP concentration in the above NPK soils only ranged from about 2 to 4 μmol ATP g −1 biomass C, in the FYM soil the microbial biomass ATP concentrations (range 11.5–13.6 μmol ATP g −1 biomass C) were the same as we repeatedly measure in fresh moist aerobic soil. We do not yet know the reasons for this. More than twice as much CO 2–C was evolved from the long-term stored soils than from freshly sampled ones. However, the specific respiration of the microbial biomass did not change much after the first 12 years of storage, indicating that loss of viability mainly occurred in the earlier years.

Pore characteristics and hydraulic properties of a sandy loam supplied for a century with either animal manure or mineral fertilizers

Abstract Application of organic residues to soil is generally assumed to improve soil tilth. Only few studies have reported the long-term effects on the more subtle aspects of soil porosity, and no reports have considered the potential effects of organic amendments on the pore system in the subsoil. We sampled undisturbed soil cores (100 cm3 and 6280 cm3) using metal cylinders in differently fertilized plots in the long-term field experiment at Askov Experimental Station, Denmark. We selected the 0–60 cm soil layer of plots dressed for a century with either mineral fertilizers (labelled NPK) or animal manure (labelled AM) and unfertilized plots (UNF) as a reference. Both fertilization treatments were studied at two levels of nutrient application: ‘normal’ (labelled ‘1’) and 1.5 times ‘normal’ (labelled ‘1½’). Water retention, air permeability and air diffusivity were measured on the small cores, and we used the large cores for measuring near-saturated and saturated hydraulic conductivity. In the plough layer, the AM and NPK soils displayed identical pore volumes in size fractions that were larger as well as smaller than 30 μm, while the UNF soil had a significantly smaller volume of pores < 30 μm. No clear trends were found in treatment effects on pore organization as calculated from air diffusivity and air permeability measurements. No significant differences in hydraulic conductivity were found in the plough layer. For the subsoil below ploughing depth, significantly larger macropore volumes and near-saturated hydraulic conductivities were found for soil of plots receiving the larger (‘1½’) amount of nutrients compared with the ‘normally’ dressed soil. This effect was independent of fertilization system (AM or NPK). We attribute the larger volume of macropores to the improved root growth conditions in the soil with the higher nutrient level. We conclude that addition of animal manure at rates realistic in agriculture has only a modest effect on soil pore characteristics of the plough layer soil compared with the use of mineral fertilizers. For the subsoil below ploughing depth, a high level of nutrient application may increase soil macroporosity and near-saturated hydraulic conductivity, but the origin of nutrients is of no significance.

The influence of mineral and organic fertilisers on the growth of the endogeic earthworm Octolasion tyrtaeum (Savigny)

Summary Endogeic earthworms play an important role in mobilisation and stabilisation of carbon and nitrogen in forest and arable soils. Soil organic matter is the major food resource for endogeic earthworms, but little is known about the size and origin of the organic matter pool on which the earthworms actually live. We measured changes in body mass of juvenile endogeic earthworms, Octolasion tyrtaeum (Savigny), in soils with different C and N contents resulting from different fertiliser treatments. The soil was taken from a long-term experiment (Statischer Dungungsversuch, Bad Lauchstadt, Germany). The treatments included (1) non-fertilised soil, (2) NPK fertilised soil, (3) farmyard manure fertilised soil and (4) NPK + farmyard manure fertilised soil. The soil was incubated in microcosms with and without one juvenile O. tyrtaeum for 80 days. Earthworm biomass decreased in non-fertilised soil by 48.6%, in NPK soil by 9.4%, but increased in farmyard manure soil by 19.7% and 42.8% (soil with additional NPK application). In farmyard manure treatments the biomass of bigger individuals decreased, but in smaller individuals it increased. In NPK fertilised soil without farmyard manure only small O. tyrtaeum increased in body mass, whereas in the non-fertilised soil all individuals decreased in body mass. Generally, soil respiration correlated positively with soil carbon content. Earthworms significantly increased soil respiration and nitrogen leaching and this was most pronounced in farmyard manure treatments. Microbial activity was generally higher in farmyard manure soil indicating that farmyard manure increases labile organic matter pools in soil. Also, biomass of earthworms and microorganisms was increased in farmyard manure soil. The presence of earthworms reduced microbial biomass, suggesting that earthworms feed on microorganisms or/and that earthworms and soil microorganisms competed for similar organic matter pools in soil. The results demonstrate that NPK fertilisation only is insufficient to sustain O. tyrtaeum , whereas long-term fertilisation with farmyard manure enables survival of endogeic species due to an increased pool of utilisable soil organic matter in arable soil.

Changes in the microbial community of an arable soil caused by long‐term metal contamination

SummaryThe effects of past applications of farmyard manure (FYM, applied from 1942 to 1967), metal‐contaminated sewage sludge (applied from 1942 to 1961) and mineral fertilizer (NPK, applied from 1942 until now) on the microbial biomass and community structure in a sandy loam, arable soil from the Woburn Market Garden Experiment, UK, were investigated in 1998. Concentrations of Cu, Ni and Zn in soils which previously received sewage sludge were less than current European Union (EU) limits, but the soil Cd concentration was more than twice the permitted limit. Organic‐C concentration in the FYM‐treated soil and contaminated soils was about twice that of NPK‐treated soil. The initial microbial biomass‐C and estimates of total bacterial numbers by acridine orange direct count were significantly (P &lt; 0.05) greater in the FYM‐treated soil compared with the NPK‐treated and the most contaminated soils. Total phospholipid fatty acid (PLFA) concentration (another measure of biomass) was significantly greater in the FYM‐treated soil compared with either the low or high metal‐contaminated soils, both of which contained similar PLFA concentrations. In the metal‐contaminated soils, in contrast, fluorescent Pseudomonas counts, as a percentage of total plate counts, were at least 1.5 times greater than in the uncontaminated soils. The concentrations of these microbial parameters were significantly (P &lt; 0.05) less in the NPK soil than in all the other treatments. Biomass‐C as a percentage of organic‐C was also significantly (P &lt; 0.05) greater in the uncontaminated soils compared with the metal‐contaminated soils. Biomass specific respiration rates in the metal‐contaminated soils were c. 1.5 times those in the FYM‐treated soil. In the metal‐contaminated soils, the concentration of mono‐unsaturated and hydroxy‐fatty acids (derived from phospholipids), and lipopolysaccharide hydroxy‐fatty acids (all indicative of Gram‐negative bacteria) were significantly (P &lt; 0.05) greater than branched fatty acids (indicative of Gram‐positive bacteria). Furthermore, Gram‐negative counts were 62–68% greater than Gram‐positive counts in the metal‐contaminated soils. Branched fatty acid concentration was significantly (P &lt; 0.05) greater in the FYM‐treated soil than in the metal‐contaminated soils. Gram‐positive counts were also 63% greater than Gram‐negative counts in the FYM‐treated soil. We found that effects of the relatively small heavy metal concentration caused measurable decreases in soil microbial biomass‐C concentrations, acridine orange direct counts and Gram‐positive counts. There were also increases in biomass specific respiration rates, and the microbial community had changed substantially, nearly 40 years after the metal inputs ceased. We conclude that, at the very least, the current EU permitted limits for heavy metals in agricultural soils should not be relaxed.

Aggregate strength and mechanical behaviour of a sandy loam soil under long‐term fertilization treatments

SummaryCurrent concern for soil quality has stimulated research on soil biological and chemical properties. In contrast, the mechanical behaviour of soil is somewhat neglected. We have examined the effects on soil mechanical properties of more than 100 years of contrasting fertilization employing three treatments from the Askov long‐term experiment: UNF (unfertilized), NPK (mineral fertilized) and AM (animal manured). We have measured tensile strength of aggregates when air‐dry and when adjusted to −10, −30 and −100 kPa pressure potential. Four aggregate size classes were investigated (1–2, 2–4, 4–8 and 8–16 mm diameter). Soil fragmentation was characterized in the field using a drop‐shatter test. Bulk soil strength was determined in the field using a shear vane and a torsional shear box. Soil texture, pH, cation exchange capacity and microbial biomass were measured. The unfertilized soil has little soil organic matter and microbial biomass and is dense. Its aggregates were strong when dry and weak when wet. In contrast, the manured soil had strong aggregates when wet and rather weak ones when dry. The NPK soil generally had intermediate properties. The differences between the soils when dry seem to be related to differences in dispersible clay content, whereas the differences when wet are related to differences in the amount of organic binding and bonding material. The optimal water content for tillage as well as the tolerable range in water content was largest in the manured soil and smallest in the unfertilized soil. Our results indicate that soil mechanical properties should be measured over a range of water regimes to determine the effects of various long‐term fertilization treatments.

Genetic analysis of the nitrogen and phosphorus utilization efficiencies in mature spring barley plants

AbstractInheritance of the efficiency of nitrogen and phosphorus utilization in grain production was studied in diallel hybrids of spring barley. Effects of varied NPK fertilization and soil moisture on the genetic variance was evaluated at maturity in pot‐ and field‐grown plants. A preponderance of general combining ability effects was found for the efficiency ratios and utilization efficiencies, suggesting that the generative efficiency indices were mainly controlled by an additive genetic system. However, the relatively high narrow‐sense heritabilities (0.33‐0.81) found under optimal conditions tended to decline to 0.00‐0.36 following water and nutrient shortages. The importance of non‐additive gene effects for utilization efficiencies was demonstrated in the field under reduced nutrition. This leads to the conclusion that the involvement of additive gene action should facilitate selection efforts only under favourable environments. Selection delayed until later hybrid generations should be used when trying to improve the nutrient efficiency of barley under less favourable nutrition conditions.

Carbon Dioxide and Methane Exchange of a Subarctic Heath in Response to Climate Change Related Environmental Manipulations

Responses of CO 2 and CH 4 exchange to NPK fertilization, soil warming and shading were investigated at a tree line heath site near Abisko in subarctic Sweden. Respiration increased with fertilization and decreased with shading after seven yr of treatment. Warming caused small overall changes in respiration. Photosynthesis was stimulated by fertilizer application to an extent which exceeded the increase in respiration and hence caused the system to increase its atmospheric CO 2 sink strength. Warming, on the contrary, tended to increase the CO 2 efflux from the ecosystem. Shading caused no significant net change in carbon flux but a significant reduction in the carbon turnover rate. Significant CH4 consumption rates suggested that subarctic heath systems may constitute a significant sink for atmospheric CH 4 . Inorganic nitrogen fertilization increased CH 4 consumption which was unexpected since N addition normally inhibits CH 4 consumption rates in natural and arable ecosystems. As expected from the relatively weak temperature dependency of microbial CH 4 oxidation reported in previous studies, warming caused no increase in CH 4 consumption rates..

Soil phosphorus dynamics in a long-term field experiment at Askov

Inorganic and organic soil P (Pi, Po) fractions were followed monthly for 15 months in a 100-year-old, fertilization and crop-rotation experiment with the Rubaek-Sibbesen, macroporous resin method, the Olsen method, and the Hedley fractionation method. Resin P, and Olsen P had similar levels and variation patterns. They increased in spring after fertilization, decreased during summer and autumn, and increased again in winter after repeated slurry applications. Resin Po decreased in spring and peaked in summer. The variation in time of the Hedley Pi and Po fractions was relatively smaller and was neither related to season nor to fertilization. Unmanured soil contained much less total P than NPK and slurry-treated soils, but the differences in total Pi were greater than those in total Po. Neither total Pi nor total Po concentrations differed between NPK and slurry treatments, indicating that Po in animal manure is quickly mineralized. All Pi and Po fractions were smaller in unmanured than in fertilized treatments. These differences were relatively largest for resin Pi and resin Po, i.e., the most labile fractions, and decreased for the medium and less labile Pi and Po fractions. The reactions by resin Pi, Olsen P, and resin Po to seasons and treatments indicate that these fractions are estimates of the most labile pools of Pi and Po in soil, which make them relevant for shortterm studies. The medium and less labile Pi and Po fractions of the Hedley fractionation method seem more relevant for long-term studies.

EFFECT OF FERTILIZER APPLICATION ON SOIL AVAILABLE NUTRIENTS, YIELD AND NUTRIENT UPTAKE OF GARLIC IN ACIDIC LATERITE SOILS OF KODAIKANAL

Graded levels of N (0,50,100 and 150 kg ha¹), P(0,25,50 and 75 kg ha¹) and K(0,25,50 and 75 kg ha¹) in selected combinations were tried as treatments besides application of zinc sulphate in the soil at 12.5 and 25 kg ha" and foliar spray at 0.5% in fractional factorial design. The two year results revealed that increased doses of application of N,P and K increased the garlic bulb yield and also the uptake of the respective nutrients. Graded levels of the major nutrients also increased the available nutrient content in the soil. A judicious combination of 100-75-50 kg NPK ha and soil application of 100-75-50 kg NPK ha and soil application of ZnSO4 at 25 kg ha' was found to be the optimum to get high yield (upto 20% ), nutrient uptake by the crop besides maintaining the soil fertility in terms of availables major nutrient contents under the conditions of acidic leteritic soils of Kodaikanal

Effect of Lucerne Hay Soil Application Foliar Spray of Juice on Yield, Nutrient Content and Uptake by IR-20 Rice

The influence of lucerne hay soil as well as foliar application of the juice revea- led that soll application of lucerne hay significantly increased the N, P and K contents in the rice grain and straw samples over absolute control and lucerne juice spray. NPK plus lucerne hay soll applied pots registered higher nutrient contents in the grain and straw of IR 20 rice as well as uptake of the nutrients than the other treatments. The available N status in the post-harvest soil samples was higher under NPK plus lucerne hay soil applied pots and that of P under NPK plus three foliar application of lucerne juice treatments. Highest available K in the soil was noticed in the pots which received the treatment NPK plus lucerne hay soil application and one foliar spray of lucerno juice on 25th day of planting.