Relationship between extracted phosphorus and sorghum yield in a Vertisol and an Alfisol under rainfed cropping

Little attention has been devoted to calibrating the soil tests for P in the field for crops grown under rainfed conditions in different soil types. Field experiments were conducted during the 1990 rainy season (June-September) at the ICRISAT Center, Patancheru (near Hyderabad), India on nearby Vertisol and Alfisol sites having a range in extractable P, for establishing relationships between extractable P and sorghum yield.In the Vertisol, 90% relative grain yield of sorghum was obtained at 2.8 mg kg^–1 Olsen extractable P while in the Alfisol, 90% relative grain yield was achieved at 5.0 mg P kg^–1 soil. These results suggest that a single critical limit of available P does not hold true for grain sorghum in the two soil types under similar agroclimatic conditions and that the critical limit is lower for the clayey Vertisol than the sandy Alfisol.     

Yield and uptake response of lettuce to cadmium as influenced by nitrogen application

A screen house experiment was conducted to determine the effect of N (0, 50, 100 and 150 mg N kg^–1) and Cd (0, 5, 10, 25 and 50 mg Cd kg^–1) on growth and concentration and uptake of N and Cd in lettuce grown for 70 days. Nitrogen application increased significantly fresh yield, dry matter yield, N concentration and uptake, whereas these parameters were significantly decreased by Cd application at all levels of N. The concentration and uptake of Cd were significantly increased by Cd application at all levels of N. This increased Cd uptake was related to increased availability of Cd in soil. Application of N upto 100 mg N kg^–1 increased Cd uptake, whereas there was sharp reduction in Cd uptake at 150 mg N kg^–1 treatment at all levels of Cd. The plant dilution effects and reduced translocation of Cd from roots to tops or the competition at the root absorption sites at highest level of N seem to be the mechanisms responsible for N suppressed Cd uptake in this study.     

Growth and yield responses of dryland grain sorghum to nitrogen and phosphorus fertilization in a ferruginous tropical soil (Haplustalf)

Field trials were conducted during the 1980–82 seasons to study the response dryland sorghum to nitrogen and phosphorus fertilization in a ferruginous tropical soil. Treatments tested were factorial combinations of three rates of nitrogen (0, 60 and 120 kg N ha^–1) and four rates of phosphorus (0, 11, 22 and 33 kg P ha^–1). Grain and straw yields and yield components were enhanced by nitrogen fertilization in two out of three years. The optimum N rate for grain yield was 60 kg N ha^–1 while straw yield responded up to 120 kg N ha^–1. The optimum P rate for dryland sorghum was 11 kg P ha^–1. Both N and P enhanced grain weight per head, grain number, test weight and tillering significantly but it was only N which enhanced 1000-grain weight and flag leaf area. Dry matter productin was increased by N fertilization but not by P. There were no significant N × P interactions for any of the parameters studied. Dryland sorghum response to N and P fertilization was influenced by season, time of planting and rainfall distribution.     

Boron uptake and toxicity in wheat in relation to zinc supply

Zinc deficiency may enhance B absorption and transport to such an extent that B may possibly accumulate to toxic levels in plant tops. Therefore, a screen house experiment was conducted to investigate the effect of B levels (0, 2.5, 5.0, 7.5 and 10 mg B kg^–1 soil) as influenced by Zn levels (0, 10 and 20 mg Zn kg^–1 soil) on DM yield of wheat tops and tissue concentration and uptake of B, Zn, Cu, Mn, Fe, Ca, Mg, K and P. Application of B decreased the dry matter yield of wheat significantly at all levels of Zn. Conversely, increasing levels of Zn increased the wheat yield significantly. The application of B increased the tissue concentration and uptake of B by wheat plants more in the absence than in the presence of Zn application. Consequently, concentration of B in wheat plants decreased with increasing levels of Zn application to the soil. This decrease in tissue B concentration was not only due to increased growth of wheat plants. Zinc application appears to have created a protective mechanism in the root cell environment against excessive uptake of B, as evidenced by the reduction of B uptake in Zn treated plants. The uptake of Mn, Mg and P decreased while the uptake of Cu, Fe, and K by wheat plants increased with Zn application. Whereas, the uptake of all nutrients (Cu, Fe, Mn, Ca, Mg, K and P) decreased significantly with the application of B. However, this depressive effect of B on nutrient uptake was less marked in the presence of applied Zn.     

Response of rice cultivars to phosphorus supply on an oxisol

Genotypic differences in absorption or utilization of P might be exploited to improve efficiency of fertilizer use or to obtain higher productivity on P-deficient soils. The objective of this study was to evaluate responses by 75 genotypes of upland rice (Oryza sativa L.) to two soil P levels in two field experiments. In the first experiment, soil P levels (Mehlich 1) were 1.5 mg kg^–1 and 5 mg kg^–1, and in the second experiment, 3 mg kg^–1 and 4.7 mg kg^–1 of soil, respectively. Rice cultivars differed significantly in shoot dry matter production at flowering, grain yield, and plant P status. Based on a grain yield efficiency index, cultivars were classified as P-efficient or P-inefficient. Shoot dry matter was more sensitive to P-deficiency but was not related to grain yield. Phosphorus use efficiency was higher under the low P treatment. Phosphorus uptake was significantly correlated with dry matter, P concentration and P-efficiency ratio. Results of this study indicate that genetic differences in P-use efficiency exist among upland rice cultivars and may be exploited in breeding programs.Contribution from National Rice and Bean Research Center of EMBRAPA, Goiania, Goias, Brazil and Appalachian Soil and Water Conservation Research Laboratoy, Beckley, WV, USA.     

Response of sorghum to fertilizer phosphorus and its residual value in a Vertisol

The response of crops to added P in Vertisols is generally less predictable than in other soil types under similar agroclimatic conditions. Very few studies have considered the residual effects of P while studying responses to fresh P applications. Field experiments were conducted for three years to study the response of sorghum to fertilizer P applied at 0, 10, 20 and 40 kg P ha^–1, and its residual value in a Vertisol, very low in extractable P (0.4 mg P kg^–1 soil), at the ICRISAT Center, Patancheru (near Hyderbad), India. In order to compare the response to fresh and residual P directly in each season, a split-plot design was adopted. One crop of sorghum (cv CSH6) was grown each year during the rainy season (June-September).The phenology of the sorghum crop and its harvest index were greatly affected by P application. The days to 50% flowering and physiological maturity were significantly reduced by P application as well as by the residues of fertilizer P applied in the previous season. In the first year of the experiment, sorghum grain yield increased from 0.14 t (no P added) to 3.48 t ha^–1 with P added at the rate of 40 kg P ha^–1. Phosphorus applied in the previous year was 58% as effective as fresh P but P applied two years earlier was only 18% as effective as fresh P.     

Reducing fertilizer requirements for hybrid squash (Cucurbita maxima L.) with localized applications of phosphorus and potassium and use of partially acidulated phosphate rock

Two experiments examined options for reducing the inputs of P and K fertilizers for hybrid squash (Cucurbita maxima L.) at Pukekohe, New Zealand. The first experiment examined the effects of elevating the NaHCO₃-soluble P from 32 to 130 mg kg^–1 and the exchangeable K from 140 to 350 mg kg^–1 within strips from 0 to 0.75 m around rows of hybrid squash planted 1.5 m apart. From both P and K, crop yield increased as the width of the fertilized strip was increased up to 0.25 m, while wider fertilized strips had no further effect. These results followed similar effects on plant dry matter and tissue P or K concentration during early growth, and are explained in terms of the P and K accumulation by the crop, the decline during growth of the sensitivity of the crop to soil P and K fertility associated with declining rates of P and K uptake per unit length of root. Implications for fertilizer management for hybrid squash are also discussed.The second experiment compared the effects of partially acidulated phosphate rock and triple-superphosphate on soil P fertility, growth and yield of hybrid squash. Partially acidulated phosphate rock had smaller effects than those of triple-superphosphate on NaHCO₃-soluble P levels in the soil, plant dry weight and tissue P concentration soon after emergence, and subsequently crop yield. On average, partially acidulated phosphate rock increased crop yield by about 70% of that following the application of the same quantity of P as triple-superphosphate. This lower effectiveness of partially acidulated phosphate rock for hybrid squash is explained in terms of its lower solubility and hence smaller effect on NaHCO₃-soluble P in the soil during early growth, when the crop is most sensitive to soil P fertility.     

Effect of nitrogen,phosphorus and molybdenum application on growth and symbiotic N2-fixation of groundnut in an acid sandy soil in Niger

Two field experiments were conducted in 1988 and 1989 on an acid sandy soil in Niger, West Africa, to assess the effect of phosphorus (P), nitrogen (N) and micronutrient (MN) application on growth and symbiotic N₂-fixation of groundnut (Arachis hypogaea L.). Phosphorus fertilizer (16 kg P ha^–1) did not affect pod yields. Addition of MN fertilizer (100 kg Fetrilon Combi 1 ha^–1; P + MN) containing 0.1% molybdenum (Mo) increased pod yield by 37–86%. Nitrogen concentration in shoots at mid pod filling (72 days after planting) were higher in P + MN than in P – MN fertilizer treatment. Total N uptake increased from 53 (only P) to 108 kg N ha^–1 by additional MN application. Seed pelleting (P + MoSP) with 100 g Mo ha^–1 (MoO₃) increased nitrogenase activity (NA) by a factor of 2–4 compared to P treatment only. The increase in NA was mainly due to increase in nodule dry weight and to a lesser extent to increase in specific nitrogenase activity (SNA) per unit nodule dry weight. The higher NA of the P + MoSP treatment was associated with a higher total N uptake (55%) and pod yield (24%). Compared to P + MoSP or P + MN treatments application of N by mineral fertilizer (60 kg N ha^–1) or farmyard manure (130 kg N ha^–1) increased only yield of shoot dry matter but not pod dry matter. Plants supplied with N decreased soil water content more and were less drought tolerant than plants supplied with Mo. The data suggest that on the acid sandy soils in Niger N deficiency was a major constraint for groundnut production, and Mo availability in soils was insufficient to meet the Mo requirement for symbiotic N₂-fixation of groundnut.     

Mono- and diammonium phosphates and triple superphosphate as sources of P in a calcareous soil

Recovery of phosphorus from monoammonium phosphate (MAP), diammonium phosphate (DAP) and triple superphosphate (TSP), at rates of 0, 15, 30, or 45 mg P kg^–1 was determined in a pot experiment on a Calcaric Lithosol soil (21% CaCO₃). At the 15 mg P kg^–1 rate DAP was as effective as MAP and more effective than TSP in supplying P, but it was less effective than MAP and TSP at the higher rates of 30 and 45 mg P kg^–1. At the two higher P rates residual bicarbonate extractable P was also significantly lower with DAP. Yield dry matter was not affected by the source of P.     

Single superphosphate depresses molybdenum uptake and limits yield response to phosphorus in groundnut (Arachis hypogaea L.) grown on an acid sandy soil in Niger,West Africa

The effect of phosphorus (P) fertilization on dry matter production and nitrogen (N) uptake of groundnut (Arachis hypogaea L.) was studied during the growing seasons of 1989, 1990 and 1991 under rainfed conditions on an acid sandy soil in Niger, West Africa. Annual application of 16 kg P ha^–1 as single superphosphate (SSP) failed to increase the total dry matter production significantly in all three years.Fertilization with SSP increased the concentrations of P and sulfur (S) in shoots from deficiency to sufficiency levels. It decreased the already very low concentrations of molybdenum (Mo), especially in the nodules, and also the N concentration in the shoot dry matter.With SSP application, total N uptake declined over three years. Foliar application of P and soil application of triple superphosphate (TSP) enhanced dry matter production, N and Mo uptake.Although these acid sandy soils are known to be deficient in P and S, care must be taken in using SSP in groundnuts as it may induce Mo deficiency, unless supplementary Mo is applied.ICRISAT Journal Article No. 1230     

Zinc and nitrogen interaction in wheat grown in limed and unlimed acid alfisol

A green house experiment was conducted to study the interaction effect of Zn and N in wheat (S-308). Zinc was applied as ZnSO₄.7H₂O at 0, 5, 10 and 20 mg per kg, and nitrogen as urea at 0, 75 and 150 mg per kg. In the absence of added N and lime 5 mg Zn per kg increased the grain, straw and root weight, but the application of either N (75 and 150 mg per kg) or lime (4000 mg CaCO₃ per kg), 10 mg Zn per kg responded significantly. However, when N and lime were added together, 20 mg Zn per kg increased the grain, straw and root weight significantly. Irrespective of Zn and N, the grain, straw and root weights were higher in limed that in unlimed soils.The application of N increased the Zn concentration in wheat tops and roots in unlimed soils, and decreased it in limed soils. However, because of an increase in wheat yield, the uptake of Zn by wheat tops and roots also increased with N application both in limed and unlimed soils. The addition of Zn to 10 mg per kg, increased the N concentration in the absence of N, but in the presence of N, the addition of Zn to 20 mg per kg decreased the N concentration in wheat tops and roots. The applied Zn to 10 mg per kg in unlimed soils and to 20 mg per kg in limed soils increased the N uptake by wheat tops and roots, respectively. The Zn concentration was higher in absence of lime than in its presence while a reverse trend was true for N concentration.     

Growth rate,yield and nitrogen uptake response of grain sorghum (Sorghum bicolor (L) Moench) to nitrogen rates in humid subtropics

Field experiments were conducted during wet seasons (June to October) of 1974, 1976 and 1977 to determine the response of newly developed hybrids and varieties of grain sorghum to N fertilization under humid subtropical conditions of Pantnagar in India. In addition to the enhancement in flowering and maturity stages brought about by N application, it also resulted in increased plant dry weight, translocation coefficients, grain yield plant^–1 and grain yield ha^–1. Varietal differences existed with respect to their responses for yield and N uptake to N rates. Most of the entries responded up to 120 kg N ha^–1. Hybrid CSH 5 utilized applied N more efficiently than other varieties.Publication No 1612 of GBPUA and T, Experiment Station, Pantnagar.     

Comparison of efficiency of Mussoorie partially acidulated phosphate rock and single superphosphate in a shallow Alfisol of the Indian semiarid tropics

The agronomic effectiveness of a partially acidulated phosphate rock (PAPR) was measured in a field experiment with sorghum (Sorghum bicolor cv. CSH-6) in a shallow Alfisol at the ICRISAT farm, Patancheru (Hyderabad), India. The experiment compared PAPR with single superphosphate. The PAPR was made by acidulating an indigenous Indian phosphate rock (Mussoorie) with H₂SO₄ at 50% acidulation level. P response was evaluated at a single relatively high N rate (120 kg ha^–1) with five rates of P (0, 2.2, 4.4, 8.8, and 17.6 kg P ha^–1). A significant response to P was obtained at rates up to 17.6kg P ha^–1.There was no significant difference due to source of P in terms of sorghum grain yield or total P uptake. Both Olsen and Bray 1 soil tests underestimated P availability from PAPR with respect to that from SSP.A rapid rate of P uptake was observed during grain filling to maturity (81–102 days), when 40% of the total P was taken by the plant. The internal efficiency of both P sources was the same.     

Critical levels of Mn in coarse textured rice soils in India for predicting response of barley to Mn application

Green house studies of 20 soils, having a range in DTPA extractable Mn, were made to determine the critical deficiency level of Mn for predicting response of barley to Mn application. Soil Mn was significantly related with both Bray's per cent dry matter yeild (r = 0.70^**) and Mn uptake (r = 0.65^**). Soil application of 25 mg Mn kg^–1 soil significantly increased yield. Both graphical and statistical models of Cate and Nelson indicated the critical level to be 2.05 mg kg^–1 soil of DTPA extractable Mn. The critical Mn deficiency level in 45 day barley plants was 18.6 mg kg^–1 dry matter. The predictability of soil and plant critical Mn level was 91 and 80 per cent respectively.     

Early growth and N2-fixation of leucaena and gliricidia at different levels of phosphorus application

The phosphorus (P) uptake and use efficiency in relation to N₂ fixation and growth of three provenances of gliricidia (Gliricidia sepium) two cultivars of leucaena (Leucaena leucocephala) and one ofL. diversifolia, all inoculated withRhizobium, were determined at five levels of P application. Increasing the P application rate resulted in a 33% increase in dry matter and total N ofL. diversifolia and an 18% dry matter increase of gliricidia provenance 13/84 over the control without P. Leucaena K8, which did not respond to P application, yielded as well with low P asL. diversifolia at the high P indicating the lower P requirement of cultivar K8. Leucaena cultivar Singapore did not yield well at either low or high P. Correlation analyses showed that differences between species and cultivars/provenances for P uptake per plant were largely related to differences in shoot growth rate and the distribution of P between roots and tops. P use efficiency was not related to dry-matter production. Genetic control of P and dry matter distribution of is probably more important than P availability in the growth media for gliricidia and leucaena provenances or cultivars. Increasing the P application rate significantly increased the number and mass of nodules in leucaena cultivars and gliricidia provenances. Significant increases in the proportion of N derived from atmospheric N₂ (% Ndfa) due to low P application (20 mg P kg^–1 soil) were observed within leucaena but not for gliricidia provenances. No significant increases in % Ndfa occurred with higher P application rates suggesting that symbiotic N₂ fixationper se is stimulated only with low rates of P.     

Effect of K on nitrogen fixation of intercrop groundnut and the competition between intercrop groundnut and maize

Application of adequate level of K has shown to improve the competitive ability of the legume in legume/grass mixtures. However, the effect of K on the competitive ability of grain legumes in legume/cereal intercropping systems has not been adequately studied. Hence, studies were made to ascertain if the effects of K could be exploited in improving the performance of groundnut (Arachis hypogaea L.) cv. No. 45 when intercropped with maize (Zea mays L.) cv. Badra. The study was conducted at the Faculty of Agriculture, University of Ruhuna, Kamburupitiya, Sri Lanka in 1988 in basins filled with 36 kg of soil. It involved establishing maize and groundnut as monocrops and as intercrops at three K levels viz. 0, 20 and 40 mg of K kg^–1 of soil. Monocrop maize and groundnut had 2 and 5 plants/basin, respectively while the intercrop had 1 maize plant and 3 groundnut plants/basin. The soil used was Red Yellow Podzolic which was tagged by incorporating¹⁵N-labelled plant material. When grown as a monocrop, K had no effect on the percent N derived from atmosphere, amount of N₂ fixed, dry matter production, pod yield and total N content of groundnut. However, when intercropped with maize lack of K application affected the above parameters significantly which was overcome by improving K level. Thus, the optimum level of K for groundnut was greater when intercropped than monocropped. A significant interaction between K level and cropping system was evident with regard to N₂ fixation, pod yield and total dry matter production of groundnut. Intercrop maize derived 30–35% of its N content from the associated groundnut plants which amounted to 13–22 mg N/plant. The amount of N supplied by groundnut to associated maize plant was not affected by K level. It appears that there is scope for alleviating growth depression of the legume component in legume/cereal intercropping systems by developing appropriate K fertilizer practices.     

Nitrogen uptake by autumn sown sugar beet

The influence of N fertilizer rate on uptake and distribution of N in the plant,¹⁵N labelled fertilizer uptake and sugar yield were studied for 3 years on autumn sown sugar beet (Beta vulgaris L.) under Mediterranean (Southern Spain) rain-fed and irrigated conditions. Available average soil N prior to sowing was 69 kg N ha^–1, and net mineralisation in the soil during the growth period was 130 kg N ha^–1. Maximum N uptake occurred in the spring and increased with increasing fertilizer rates in the irrigated crop. There was no increase in N uptake in the sugar beet cropped under rain-fed conditions because of water shortage. Maximum average N uptake both by roots and tops was between 200 and 250 kg N ha^–1. When N fertilizer was not applied, average uptake from the soil was between 130 and 140 kg N ha^–1. At the end of the growth period there was a marked translocation of N from the leaves to the root which increased with the N fertilizer rate. The N ratio top/roots at harvest was 0.45–0.5 and 0.8- - 1 in the irrigated and rain-fed sugar beet, respectively. Maximum¹⁵N labelled fertilizer uptake took place in May-June, being larger in irrigated sugar beet or when spring rainfall was more abundant. Fertilizer use efficiency varied between 30% and 68%. Sugar yield response to N fertilizer rates depended on the N available in the soil and on the total water input to the crop, particularly in spring. The response was more constant in the irrigated crop, where optimum yield was obtained with a fertilizer rate of 160 kg N ha^–1. In the rain-fed crop, the optimum dose proved more erratic, with an estimated mean of 100 kg N ha^–1. The amount of N required to produce 1 t of root and of sugar ranged between 1.5 and 3.8 kg N and between 11.1 and 22.4 kg N respectively, and varied according to the N fertilizer rates applied.     

The effect of fertilizer placement on nitrogen uptake and yield of wheat and maize in Chinese loess soils

Field trials were carried out to study the fate of¹⁵N-labelled urea applied to summer maize and winter wheat in loess soils in Shaanxi Province, north-west China. In the maize experiment, nitrogen was applied at rates of 0 or 210 kg N ha^–1, either as a surface application, mixed uniformly with the top 0.15 m of soil, or placed in holes 0.1 m deep adjacent to each plant and then covered with soil. In the wheat experiment, nitrogen was applied at rates of 0, 75 or 150 kg N ha^–1, either to the surface, or incorporated by mixing with the top 0.15 m, or placed in a band at 0.15 m depth. Measurements were made of crop N uptake, residual fertilizer N and soil mineral N. The total above-ground dry matter yield of maize varied between 7.6 and 11.9 t ha^–1. The crop recovery of fertilizer N following point placement was 25% of that applied, which was higher than that from the surface application (18%) or incorporation by mixing (18%). The total grain yield of wheat varied between 4.3 and 4.7 t ha^–1. In the surface applications, the recovery of fertilizer-derived nitrogen (25%) was considerably lower than that from the mixing treatments and banded placements (33 and 36%). The fertilizer N application rate had a significant effect on grain and total dry matter yield, as well as on total N uptake and grain N contents. The main mechanism for loss of N appeared to be by ammonia volatilization, rather than leaching. High mineral N concentrations remained in the soil at harvest, following both crops, demonstrating a potential for significant reductions in N application rates without associated loss in yield.     

Critical manganese deficiency level for soybean grown in Ustochrepts

A greenhouse study with 15 soils, having a range in DTPA extractable Mn, was conducted to determine the critical deficiency level of Mn in Ustochrepts for predicting response of soybean to Mn application. Soil application of 10 mg Mn kg^–1 soil significantly increased the dry matter yield in deficient soils. Soil Mn was significantly related with Bray's per cent yield (r = 0.72^**) and Mn uptake (r = 0.75^**). Both graphical and statistical models of Cate and Nelson indicated the critical level to be 3.3 mg kg^–1 soil of DTPA extractable Mn. Critical Mn deficiency level in recently matured terminal leaflet blade at V6 growth stage in soybean plant was 22.0µg g^–1 dry matter. The predictability of soil and plant critical Mn level was 87 per cent.     

Phosphorus fertigation of trickle-irrigated potato

A 3-year field study, on Pellic Vertisol, investigated the response of trickle-irrigated potato (Solanum tuberosum L.) to four P levels applied with the irrigation water. Waters supplied with 130 and 120 mg l^–1 of N and K, respectively, and with P levels of 0, 20, 40 and 60 mg l^–1, were applied when the soil water potential was between 0.03 and 0.04 MPa. The water applied at each irrigation was equivalent to 0.8 of pan evaporation from a screened USWB Class A pan. With the application of 40 mg P l^–1 no P accumulation deeper in the soil profile occurred, whereas P in petioles was at levels recommended for high yield of good quality. At this P concentration in irrigation water, removal of P from soil by tubers was 22 kg/ha/year. The highest yield of good quality was obtained at 40 mg P l^–1.