Phosphorus Placement Research Articles

Disponibilidade de zinco para milho em resposta à localização de fósforo no solo

A aplicação de P no solo pode afetar a disponibilidade de Zn para as plantas, dependendo de sua localização. Com o objetivo de avaliar a resposta de milho à adição de Zn no solo e determinar seu nível crítico no solo e na planta, em relação à localização de P, em amostras de dois solos de Minas Gerais, realizou-se um ensaio em casa de vegetação. O experimento consistiu em um arranjo fatorial (2 x 3 x 6), correspondendo a dois solos (Latossolo Vermelho Amarelo variação Una e Argissolo Vermelho Amarelo, doravante denominados LU e PVA, respectivamente); três modos de localização de P (5, 10 e 30% do volume total do solo na dose de 200 mg dm-3) e seis doses de Zn (0, 1, 2, 4, 6 e 8 mg dm-3). Determinaram-se a produção de matéria seca e os teores de Zn na parte aérea das plantas de milho. A adição de Zn aumentou linearmente (p < 0,01) o teor do elemento no solo e a absorção pela planta. No solo LU os níveis críticos variaram de 0,91 a 2,13 mg dm-3 de Zn pelo extrator Mehlich-1 e, na planta, de 18,0 a 24,6 mg kg-1. Esses níveis foram maiores quando as aplicações de P foram localizadas em menor volume de solo. A localização de P afetou o teor de Zn na Planta. No solo LU, quando o P foi localizado no menor volume de solo e na ausência de Zn, as plantas de milho apresentaram elevados teores de P.

Effect of form, placement and rate of N fertilizer, and placement of P fertilizer on wheat in Saskatchewan

On the Canadian prairies, the one-pass seeding and fertilizing no-till system is very common. However, the close proximity of the fertilizer to the seed can cause damage to the emerging seedlings due to a combination of a salt effect and/or ammonia toxicity. Manufacturers have responded by developing openers that allow placement of seed and fertilizer in separate bands. A 3-yr study was initiated in 2000 to determine the effect of nitrogen (N) form [urea (U) and anhydrous ammonia (AA)], placement [broadcast (Br), side-band (SB) or mid-row band (MRB)], timing (fall or spring) and rate (0 to 90 or 120 kg N ha-1), and phosphorus (P) placement (7 to 10 kg P ha-1) on plant density, seed and straw yield, seed protein content, and N uptake of spring wheat (Triticum aestivum L.) under no-till at four sites representing different agro-ecological zones in Saskatchewan. Rate of applied N had the most dominant effect on agronomic variables, while form, placement, and timing of application of N had minor effects. Generally, SB and MRB were comparable in terms of seed yield, N uptake and seed protein content. From a practical perspective, SB and MRB could be used with equal success with either U or AA. Side banding P produced responses similar to seed-placed P, except under very dry conditions where side banding was superior. In general, placement of urea in soil in a band was more effective than broadcasting, while fall banding can be less effective than spring banding.Key words: Anhydrous ammonia, N application timing, N form, N and P placement, N uptake, protein content, urea, wheat, yield

Effect of Long‐Term Fertilization and Placement of Phosphorus on Barley Yields

An experiment that was established in 1982 to assess placement of phosphorus (P) fertilizer on the yield of continuous barley was terminated in 2004, after annual application of P (30 kg ha−1) was discontinued in all but one treatment in 2002. Total removal of P during the first 20 years of the experiment (615 kg P2O5 ha−1) was virtually equal to total P application (600 kg P2O5 ha−1); however, when removal by the control that was fertilized with N only was subtracted from the total removal, a residual P component of 474 kg P2O5 ha−1 was obtained as a result. In spite of this, discontinuing P fertilization after 20 years resulted in significant reduction in barley grain yield that was greater in the treatments where P was seedrow placed (21%) than where P was either banded (12%) or one third seedrow placed and two thirds banded (15%). Four‐week burial of anion PRSTM probes in 2006 allowed us to ascertain the reasons for these differences that reflected management and P placement practices. The use of PRS probes allowed us to interpret more than 90% of variations both in P removal and yield of barley over the duration of the experiment.

Effect of fertilizer nitrogen management and phosphorus placement on canola production under varied conditions in Saskatchewan

No-till (NT) requires all fertilizer nutrients to be applied during planting, but high rates of fertilizer nitrogen (N) in close proximity to the seed can negatively affect seedling development; therefore, different placement technologies have been developed to place seed and N in a single operation while maintaining an adequate separation between them. We conducted a 3-yr field study (2000 to 2002) at four sites in Saskatchewan. The objective was to determine the effects of N fertilizer form [urea (U) and anhydrous ammonia (AA)], placement [broadcast, side-band (SB) and mid-row band (MRB)], timing (fall vs. spring), rate (0 to 90 or 120 kg N ha-1), and P fertilizer placement on yield, seed protein content and N uptake in canola. The N fertilizer managements had no significant effect on crop emergence. Yield, seed protein concentration and N uptake increased with increasing N fertilizer rate. Seed protein was significantly higher on SB compared with MRB and on U compared with AA. Seed yield and seed and straw N uptake were higher when U was SB compared with broadcast. Plant density was higher when P was placed in SB rather than with the seed, but the reverse was true for seed yield and seed N uptake. Key words: Anhydrous ammonia, N timing, N form, N and P placement, N uptake, yield

Pear Responses to Split Fertigation and Band Placement of Nitrogen and Phosphorus

Single broadcast application of nitrogen (N) and phosphorus (P) on the soil surface results in low use efficiency of applied N and P in pear (Pyrus communis) production systems in Oregon and the Pacific northwestern United States. A field experiment was conducted from 2005 through 2006 to evaluate the effects of split fertigation and band placement as alternate N and P management practices in ‘Anjou’ pears growing on a Parkdale loam soil near Parkdale, OR. Measurement and analysis of tree nutrition, fruit yield, quality, and storability, as well as indigenous soil nutrient supply was the scope of the experiment. To evaluate fertilizer management practices on pear growth and productivity, the following four treatments were tested with a randomized complete block design replicated four times: 1) broadcast application of N and P on the soil surface in a 10-ft-wide, weed-free strip centered on the tree row, 2) band placement of N and P on both sides of tree rows in 1 × 1-ft ditches (width × depth), 3) 1 × 1-ft ditches were dug using the band placement equipment, the dug soil was completed returned to the ditch without any fertilizer, and the broadcast application of N and P on the soil surface was applied on a 10-ft-wide, weed-free strip centered on the tree row, and 4) fertigation of N and P split into five equal applications throughout the growing season. Nitrogen and P fertilizers were applied to treatments 1, 2, and 3 at 100 lb/acre N and 55 lb/acre P, while treatment 4 received only 80 lb/acre N and 44 lb/acre P. The 2-year average results show leaf N and P concentrations in the fall were increased by 10.0% and 10.6%, respectively, with split fertigation compared with broadcast application on the soil surface. Band placement increased leaf N by 7.1% relative to broadcast application on the soil surface with soil disturbance caused by band placement. Split fertigation and band placement slightly increased fruit yield, but increased marketable fruit (the total of excellent and very slightly scalded fruit) by 20.9% and 11.1% (absolute value) when compared with broadcast application of N and P and broadcast application of N and P with soil disturbance caused by band placement, respectively, and after 3 months of cold storage. No detrimental effects on fruit weight or reduction in soil amino sugar N were observed from lowering the N and P application rates by 20% with split fertigation. Overall, split fertigation and band placement of N and P can be used to replace single broadcast application on the soil surface on pear orchards to reduce fruit superficial scald during cold storage and improve the use efficiency of applied N and P in the mid-Columbia region of Oregon.

Pear Responses to Split Fertigation and Band Placement of Nitrogen and Phosphorus

Single broadcast application of nitrogen (N) and phosphorus (P) on the soil surface results in low use efficiency of applied N and P in pear (Pyrus communis) production systems in Oregon and the Pacific northwestern United States. A field experiment was conducted from 2005 through 2006 to evaluate the effects of split fertigation and band placement as alternate N and P management practices in ‘Anjou’ pears growing on a Parkdale loam soil near Parkdale, OR. Measurement and analysis of tree nutrition, fruit yield, quality, and storability, as well as indigenous soil nutrient supply was the scope of the experiment. To evaluate fertilizer management practices on pear growth and productivity, the following four treatments were tested with a randomized complete block design replicated four times: 1) broadcast application of N and P on the soil surface in a 10-ft-wide, weed-free strip centered on the tree row, 2) band placement of N and P on both sides of tree rows in 1 × 1-ft ditches (width × depth), 3) 1 × 1-ft ditches were dug using the band placement equipment, the dug soil was completed returned to the ditch without any fertilizer, and the broadcast application of N and P on the soil surface was applied on a 10-ft-wide, weed-free strip centered on the tree row, and 4) fertigation of N and P split into five equal applications throughout the growing season. Nitrogen and P fertilizers were applied to treatments 1, 2, and 3 at 100 lb/acre N and 55 lb/acre P, while treatment 4 received only 80 lb/acre N and 44 lb/acre P. The 2-year average results show leaf N and P concentrations in the fall were increased by 10.0% and 10.6%, respectively, with split fertigation compared with broadcast application on the soil surface. Band placement increased leaf N by 7.1% relative to broadcast application on the soil surface with soil disturbance caused by band placement. Split fertigation and band placement slightly increased fruit yield, but increased marketable fruit (the total of excellent and very slightly scalded fruit) by 20.9% and 11.1% (absolute value) when compared with broadcast application of N and P and broadcast application of N and P with soil disturbance caused by band placement, respectively, and after 3 months of cold storage. No detrimental effects on fruit weight or reduction in soil amino sugar N were observed from lowering the N and P application rates by 20% with split fertigation. Overall, split fertigation and band placement of N and P can be used to replace single broadcast application on the soil surface on pear orchards to reduce fruit superficial scald during cold storage and improve the use efficiency of applied N and P in the mid-Columbia region of Oregon.

Phosphorus accumulation by field-grown canola crops and the potential for deep phosphorus placement in a Mediterranean-type climate

When the bulk of phosphorus (P) is located near the soil surface, spring drying of topsoil in Mediterranean-type climates can reduce P availability to crops and cause potential yield loss. In crop species that require a P supply during spring, deep-placement of P fertiliser has proved an effective method of improving P availability and grain yields; however, the spring P demand of field-grown canola (Brassica napus L.) and therefore potential response to deep P placement is not known. This study investigated the effect of deep- (0.17–0.18 m), conventional- (shallow, 0.07–0.08 m), split- (50% deep, 50% shallow), and nil-P fertiliser treatments on P accumulation and seed yields of canola in two field trials. In addition, a glasshouse experiment with different depths of P fertiliser placement and topsoil drying at different growth stages was conducted. In the glasshouse study, deep P placement resulted in greater P uptake by plants, but did not increase seed yields regardless of the time of topsoil drying. At the relatively high-soil-P field site (canola grown on residual P application from the previous year) in a dry season, there was no biomass response to any residual P fertiliser treatments, and P accumulation had ceased by mid flowering. At the low-P field site, P accumulation continued throughout flowering and silique-filling, and seed yields increased significantly (P ≤ 0.05) in the order of split- > deep- > shallow- > nil-P treatments. Improved seed yields in the split- and deep-P treatments appeared to be the direct result of enhanced P availability; in particular, P uptake during vegetative growth (winter) was higher in the treatments with deep P placement. A greater understanding of P accumulation by field-grown canola in relation to soil P properties is needed for better defining optimum P fertiliser placement recommendations.

Optimum placement of phosphorus for corn/soybean rotations in a strip-tillage system

Optimum placement of phosphorus for corn/soybean rotations in a strip-tillage system

Optimum placement of phosphorus for corn/soybean rotations in a strip-tillage system

S trip tillage, a conservation tillage system using very reduced tillage, is attracting much attention throughout the corn-growing regions of the United States. In the northern parts of the Corn Belt, strip tillage often replaces no-till systems on the more poorly drained soils because it provides a warmer tilled seedbed for early planting and faster early growth while maintaining substantial amounts of erosion-minimizing plant residue between the tilled strips. Another benefit of strip tillage is the need for only one field operation between soybean harvest and spring planting—that is, fall strip tillage accompanied by deep-placement of fertilizer phosphorus (P) and potassium (K) in a band 15 to 18 cm (6 to 7 in) deep in the strip. No preplant tillage is needed. From an environmental perspective, deep-band placement is considered to be ideal in terms of eliminating nutrient stratification and reducing the potential for surface runoff of fertilizer P, which can easily occur when fertilizers are broadcasted on the soil surface of no-till systems. From an agronomic perspective, fertilizer placement 10 to 13 cm (4 to 5 in) directly below where the seed will be planted is thought to be ideal in terms of fertilizer P and K use efficiency, early …

Long-term effect of placement of fertilizer nitrogen and phosphorus on barley yields

An experiment that was established in 1990 to assess depth and method of placement of nitrogen (N) and phosphorus (P) fertilizer on the yield of continuous barley (with 1 yr interruption with canola in 1995) was continued to 2001. Annually, 80 kg N ha-1 were banded either at 7.5 to 10 or 15 to 17.5 cm depth alone or in combination with 40 kg P2O5 ha-1; the latter was either seedrow placed or banded with the N (dual banding), or split 1/2 in the seedrow and 1/2 in the band. An unfertilized control was maintained in all years. Temperature after seeding had a marked effect on the effectiveness of depth of N and P placement as well as the method of P placement. Shallow (7.5 to 10 cm depth) placement resulted in greater yields in 8 of the 11 yr that barley was grown and was never inferior to deeper placement (15 to 17.5 cm); this advantage was directly related to cooler-than-normal temperature after seeding. Cooler-than-normal temperatures also resulted in benefits from seedrow placed P; however, benefits were not as frequent as those obtained by either dual banding or splitting P between seedrow and the band. It would appear that overall benefits from banding P together with N (dual band), independently of the depth of banding, are greater than those from seedrow placing, as those benefits from the latter are less frequent and of considerably less magnitude. Key words: Band, dual band, seedrow, shallow, deep

Influence of arbuscular mycorrhizal fungi, inoculum level and phosphorus placement on growth and phosphorus uptake of Phyllanthus calycinus under jarrah forest soil

Phosphorus uptake and biomass production may vary between arbuscular mycorrhizas (AM) species of contrasting life cycles and their modes of interaction with host plants. This research investigated differences among three AM fungi from different genera isolated from the jarrah forest with respect to their colonisation, biomass production and P uptake over time. The understorey plant Phyllanthus calycinus, has been shown to be extensively mycorrhizal. We examined differences in the capacity of fungi associated with this plant to access a P point source from increasing distances from the root. The methodology simulated “pockets” of P in forest soil. Phosphorus sources in root-exclusion mesh bags were inserted 2, 4 and 6 cm from plant roots restrained in separate mesh bags. Acaulospora laevis colonised plants to the greatest extent, producing higher plant biomass and P uptake compared to the other two fungi. Plant biomass and P uptake were enhanced where P sources were closest to the root, as expected, but there were differences among fungi in response to level of inoculum used for each fungus. The capacity of individual AM fungi to access a point source of P at different distances varied in a highly mycorrhizal native forest understorey plant in parallel with plant growth and P uptake.

The effect of phosphorus(P) placement and genotype differences on yield and yield components of maize(<i>Zea mays L.</i>)

The effect of phosphorus(P) placement and genotype differences on yield and yield components of maize(<i>Zea mays L.</i>)

Placement of nitrogen, phosphorus and potassium fertilizers by drilling in spring barley grown for malt without use of pesticides

The increasing consumer demand for food products that are produced without the use of pesticides are reflected in action plans to reduce the use of pesticides in agriculture. Most of the barley (Hordeum vulgare L.) produced is used for pig feed but some is used for malting – the primary step in the production of beer. The effects of fertilizer application method, type and rate on yield and grain quality were investigated in a malting barley crop without the use of pesticides. Twelve treatments where single and multiple nutrient fertilizers were either broadcast or placed in bands by drilling, were compared in a field experiment at two sites in Denmark during 1993–96. Weeds were controlled mechanically in all treatments, and chemical control of foliar fungal diseases and insects was only carried out in two treatments. The placement of a compound NPK-fertilizer increased the grain yield and the quality parameters grain size and grading when weeds are controlled mechanically by harrowing. The effect of fertilizer placement on grain yield and quality decreased in the order NPK > NP > N>P. Herbicide-free growing of malting barley may be possible using fertilizer placement, but the use of chemical control of foliar fungal diseases and insects may be critical when pests exceed certain thresholds as they significantly reduce grain yield, grain size and grading. The aim of growing malting barley satisfactorily without the use of pesticides was only partly met.

Root distributions of Australian herbaceous perennial legumes in response to phosphorus placement.

Many Australian plant species have specific root adaptations for growth in phosphorus-impoverished soils, and are often sensitive to high external P concentrations. The growth responses of native Australian legumes in agricultural soils with elevated P availability in the surface horizons are unknown. The aim of these experiments was to test the hypothesis that increased P concentration in surface soil would reduce root proliferation at depth in native legumes. The effect of P placement on root distribution was assessed for two Australian legumes, Kennedia prorepens F. Muell. and Lotus australis Andrews, and the exotic Medicago sativa L. Three treatments were established in a low-P loam soil: amendment of 0.15 g mono-calcium phosphate in either (i) the top 50 mm (120 µg P g-1) or (ii) the top 500 mm (12 µg P g-1) of soil, and an unamended control. In the unamended soil M. sativa was shallow rooted, with 58% of the root length of in the top 50 mm. K. prorepens and L. australis had a more even distribution down the pot length, with only 4 and 22% of their roots in the 0-50 mm pot section, respectively. When exposed to amendment of P in the top 50 mm, root length in the top 50 mm increased 4-fold for K. prorepens and 10-fold for M. sativa, although the pattern of root distribution did not change for M. sativa. L. australis was relatively unresponsive to P additions and had an even distribution of roots down the pot. Shoot P concentrations differed according to species but not treatment (K. prorepens 2.1 mg g-1, L. australis 2.4 mg g-1, M. sativa 3.2 mg g-1). Total shoot P content was higher for K. prorepens than for the other species in all treatments. In a second experiment, mono-ester phosphatases were analysed from 1-mm slices of soil collected directly adjacent to the rhizosphere. All species exuded phosphatases into the rhizosphere, but addition of P to soil reduced phosphatase activity only for K. prorepens. Overall, high P concentration in the surface soil altered root distribution, but did not reduce root proliferation at depth. Furthermore, the Australian herbaceous perennial legumes had root distributions that enhanced P acquisition from low-P soils.

Broadcast and Deep‐Band Placement of Phosphorus and Potassium for Soybean Managed with Ridge Tillage

The efficiency of broadcast and band P and K placement methods for ridge tilled soybean [Glycine Max (L.) Merr.] has not been extensively researched. This study evaluated grain yield, early plant growth, and nutrient uptake (V5–V6 stages), and soil‐test responses to broadcast and deep‐band (15–20 cm below the ridge surface) placements in 14 trials. Fertilizer rates were 0, 14, and 56 kg P ha−1 and 0, 33, and 132 kg K ha−1 A randomized complete‐block design was used. Soil‐test P (STP) was 7 to 61 mg kg−1 (Bray‐P1 test, 15‐cm depth) and soil‐test K (STK) was 100 to 197 mg kg−1 (ammonium acetate test). Phosphorus increased yield (P ≤ 0.1) at four sites. Band P was better at one site (30 kg ha−1) and broadcast P was better (40 kg ha−1) at another site. Both P placements increased dry weight (DW) at two sites. Yield and DW responses to P were observed when STP was <19 mg kg−1 Phosphorus increased plant P uptake at eight sites, and band P was better than broadcast P at three sites. Potassium increased yield at two sites, and only band K increased yield at one of these sites. Potassium increased DW at four sites, and increases were always larger for band K. Band K increased K uptake at 10 sites and broadcast K increased K uptake only at two sites. Soil‐test P in ridges predicted P sufficiency better than mean STP from ridges and valleys at two sites. Although K fertilization seldom increased yield in this study, increased plant K uptake with banding compared with broadcasting suggests that banding may be more efficient for grain production in other conditions.

Effects of source and placement of phosphorus on concentration of cadmium in the grain of two durum wheat cultivars

Cadmium is toxic to humans. Because it enters the food chain through plant uptake, application of phosphorus fertilizer carrying Cd as an impurity may increase the Cd concentration of cereal grains above proposed threshold values. Field experiments were conducted to determine the effect of two phosphorus fertilizers on Cd concentration of two durum wheat ( Triticum turgidum L. var. durum) cultivars, a low Cd accumulator (Arcola) and a high accumulator (Kyle) grown in two soils of southwestern Saskatchewan, Canada. Phosphorus was applied as monoammonium phosphate (15 mg Cd kg-1) and as triple superphosphate (75 mg Cd kg-1) at a rate of 18 kg P ha-1. The fertilizer was applied in a mid-row band or in the seed row. Nitrogen was applied as urea or as ammonium sulphate. Variability in Cd concentration was at tributed primarily to genotype and environment, which accounted for 41% and 29% of the explained variability, respectively. The Cd concentration of Arcola averaged 80 µg kg-1, while that of Kyle averaged 143 µg kg-1. In contrast, fertilization accounted for only a small proportion of the explained variability, with phosphorus treatments accounting for 3% of the model sums of squares, and N sources accounting for less than 1%. Phosphorus fertilization increased the Cd concentration of Arcola, regardless of source or placement, but the proportion of samples with Cd concentration above 100 µg kg-1 remained unchanged at 17%. In the case of Kyle the Cd concentration increased only when the fertilizer was seed-placed, but in this case the proportion of samples with Cd concentration above 100 µg kg-1 increased from 67 to 90%. The effect of P appeared to result from the effects of fertilizer on plant density and vigour rather than from Cd impurities in the fertilizer. Key words: Cadmium concentration, cadmium uptake, durum wheat, fertilization, phosphorus, fertilizer placement, phosphorus source

Fall and early spring seeding of canola (Brassica napus L.) using different methods of seeding and phosphorus placement

Fall seeding of canola has been suggested as an alternative to spring seeding in order to avoid environmental stress, foster early maturity, produce larger seed and possibly realise yield and oil content benefits. Further, the practice of broadcast-seeding canola has been introduced to save time and allow fertilizer application while seeding in fields that are wet in the spring. This study was designed to assess methods of phosphorus placement under these alternative seeding dates and methods. Canola was broadcast or seed-row placed either in the fall (14 to 28 October) or spring (26 April to 3 May) of each crop year. We assessed phosphorus fertilization for these options by either broadcasting or banding and seed-placing or side-banding 0, 20, and 40 kg P2O5 ha–1 for broadcast and row seeding, respectively. Fall seeding of canola did result in earlier maturity (7 to 10 d) and larger seed in all experiments. Spring-seeded canola provided a yield advantage (average 14% over all six experiments), especially in the three experiments carried out in the Black Soil Zone (average yield increase of 24.8%). There was a response to phosphate fertilization in three of the six sites, which were considered to be phosphorus deficient. The effectiveness of phosphate application was associated with the method of seeding and thus phosphate placement, because row-seeded canola yielded higher at the phosphorus-deficient sites. Generally, there was no interaction between the time of seeding and phosphate fertilization. The results on the impact of seeding time on oil content were inconclusive as oil content increased at one site, decreased at another and remained unchanged at the rest. Key words: Seeding date, broadcast seeding, row seeding, oil content, crop maturity

Influence of rate and method of phosphorus placement to garlic (Allium sativum L.) in a Mediterranean environment.

Influence of rate and method of phosphorus placement to garlic (Allium sativum L.) in a Mediterranean environment.

Effect of levels and mode of phosphorus and biofertilizers on chickpea (Cicer arietinum) under dryland conditions

A field experiment was conducted.during the winter seasons of 2000 2001 and 2001 2002, to study the ef fect of levels and mode of phosphorus, and biofertilizers [vesicular arbuscular mycorrhiza (VAM) and phosphate solubilizing bacteria (PSB)] on yield attributes and yield of chickpea (Cicer arietinum L.). Inoculation of biofertilizers significantly increased yield attributes of podslplant and seedslplant and yield of chickpea. Among biofertilizers, dual inoculation of PSB VAM markedly enhanced these yield attributes and yield compared with PSB or VAM alone. Application of phosphorus from 0 to 60 kg P,OJha resulted in linear increase in yield at tributes and yield. Aqua placement of phosphorus significantly increased grain yield in first year only.

Effects of tillage and phosphorus placement on phosphorus runoff losses in a grain sorghum-soybean rotation.

Phosphorus enhances eutrophication of fresh water bodies. This study was conducted to determine the influence of tillage and P placement on P losses in runoff water from a somewhat poorly drained soil (Woodson silt loam [fine, smectitic, thermic Abruptic Argiaquoll], 1.0-1.5% slope) in a grain sorghum [Sorghum bicolor (L.) Moenchl-soybean [Glycine mar (L.) Merr] rotation. Chisel-disk-field cultivate (ChT), ridge-till (RT), and no-till (NT) in combination with 0 kg P ha(-1) or 24 kg P ha(-1) broadcast or knifed (applied prior to planting grain sorghum) were studied. Runoff volume and losses of sediment and P were summed over the growing season. Significant interactions between tillage and P placement for soluble P losses were found. For example, soluble P loss in 1999 for NT-broadcast in grain sorghum was 358 g ha(-1); significantly greater than 31 g ha(-1) for NT-knife or 23 g ha(-1) for NT-check. Similar results were found for RT but no such differences were found for ChT. Bioavailable P losses were generally highest with broadcast P placement and for NT and RT. Total P losses were significantly higher at 959 g ha(-1) with broadcast P on grain sorghum in 1998, compared with 521 g ha(-1) for the check and 659 g ha(-1) for the knifed P applications. Total P losses in 1999 for soybeans were only 18 g ha(-1) for NT, which was significantly lower than 75 g ha(-1) for ChT and 66 g ha(-1) for RT. The results indicate that broadcast P applications on RT and NT will increase P losses, but the influence of tillage was not consistent.