Phosphorus Nutrition of Upland Rice,Dry Bean,Soybean, and Corn Grown on an Oxisol

Rice, dry bean, corn, and soybean are important food crops. Phosphorus (P) deficiency is one of the most yield-limiting factors for these crops grown on highly weathered Brazilian Oxisols. Four greenhouse experiments were conducted to determine P requirements of these four crops. The P levels used were 0, 50, 100, 200, and 400 mg kg^?1. Growth, yield, and yield components evaluated of four crop species were significantly increased with the application of P fertilization. Most of the responses were quadratic in fashion when the P was applied in the range of 0 to 400 mg kg^?1. Maximum grain yield of upland rice was obtained with the application of 238 mg P kg^?1 of soil, maximum dry bean grain yield was obtained with the application of 227 mg P kg^?1 of soil, and maximum grain yield of soybean was obtained with the application of 224 mg P kg^?1 of soil. Maximum shoot growth of corn was obtained with the addition of 323 mg P kg^?1 of soil. Most of the growth and yield components had significant positive association with grain yield or shoot dry weight. Phosphorus concentration and uptake were greater in the grain compared to straw in upland rice and dry bean plants. Overall, P-use efficiencies decreased with increasing P rates.     

Growth,yield and yield components of dry bean as influenced by phosphorus in a tropical acid soil

Phosphorus (P) deficiency is one of the most yield limiting factors for dry bean (Phaseolus vulgaris) production in tropical acid soils. Dry beans are invariably grown as mono-crops or as inter-crops under the perennial tropical crops. Information is limited regarding the influence of phosphorus fertilization on dry bean yield and yield components and P use efficiency in tropical acid soils. A greenhouse experiment was conducted to evaluate the influence of phosphorus fertilization on dry bean growth, yield and yield components and P uptake parameters. Phosphorus rates used were 0, 50, 100, 150, 200, and 250 mg P kg^?1 of soil. Soil used in the experiment was an acidic Inceptisol. Grain yield, shoot dry weight, number of pods, and 100 grain weight were significantly (P < 0.01) increased with phosphorus fertilization. Maximum grain yield, shoot dry matter, number of pods, and 100 grain weight were obtained with the application of 165, 216, 162, and 160 mg P kg^?1 of soil, respectively, as calculated by regression equations. Grain yield was significantly and positively associated with shoot dry weight, number of pods, P concentration in grain and total uptake of P in shoot and grain. Phosphorus use efficiency defined in several ways, decreased with increasing P rates from 50 to 250 mg P kg^?1 of soil. Maximum grain yield was obtained at 82 mg kg^?1 of Mehlich 1 extractable soil P. Results suggest that dry bean yield in Brazilian Inceptisols could be significantly increased with the use of adequate rates of phosphorus fertilization.     

Growth and Zinc Uptake and Use Efficiency in Food Crops

Zinc (Zn) deficiency in annual crops is very common in Brazilian Oxisols. Data are limited on Zn uptake and use efficiency during crop growth cycles. A field experiment was conducted during two consecutive years with the objective to determine shoot dry weight and Zn uptake and use efficiency in upland rice, dry bean, corn, and soybean during growth cycles. Shoot dry weight of four crops was significantly increased in an exponential quadratic fashion with increasing plant age. Rice and corn had higher shoot dry weights and grain yields than dry bean and soybean. Zinc concentration in rice and corn decreased in a quadratic fashion with increasing plant age. However, in dry bean and soybean, Zn concentration had a quadratic increase. Zinc uptake followed an exponential quadratic response in four crops, and it was higher in corn and upland rice than in dry bean and soybean. Zinc use efficiency in shoot dry‐weight production had significant quadratic responses in upland rice and soybean with increasing plant age. In corn, Zn use efficiency for shoot dry‐weight production was linear as a function of plant age. Zinc use efficiency for grain production was maximum for corn and minimum for soybean. Hence, cereals had higher Zn use efficiency than legumes.

Zinc concentration in grain of dry bean and soybean was higher than in upland rice and corn, which is a desirable quality factor for human consumption so as to avoid Zn deficiency.     

Phosphorus Use Efficiency in Upland Rice Genotypes Under Field Conditions

Phosphorus (P) deficiency is one of the most yield limiting factors for crop production in South American soils. Upland rice (Oryza sativa L.) is an important crop in South American cropping systems, including Brazil. A field experiment was conducted with the objective to evaluate 20 upland rice genotypes for phosphorus (P) use efficiency. The P rate used was low (0 kg P ha^?1) and high [87 kg P ha^?1 or 200 kg phosphorus pentoxide (P₂O₅) ha^?1]. Plant height, shoot dry weight, grain yield, panicle number, 1000 grain weight, spikelet sterility, and grain harvest index were significantly influenced by P and genotype treatments. The P X genotype interaction was significant for grain yield, indicating that genotypes responded differently under two P rates. Overall, grain yield increased by 12% with the addition of P fertilization. Based on grain yield efficiency index, genotypes were classified into efficient, moderately efficient, and inefficient group. The genotypes that were classified as efficient in P use were BRA032048, BRA042094, BRA02601, BRA032051, BRA032033, BRA052015, BRA042156, BRA01600, BRA01506, BRA052023 and BRA042160. The inefficient genotypes in P us efficiency were BRS Primavera, BRA052045, BRA01596, and BRS Sertaneja. Grain harvest index had a significant positive association with grain yield and spikelet sterility had a significant negative association with grain yield, as expected. Average, P-use efficiency of five genotypes was about 17 kg kg^?1 (kg grain yield per kg P applied).     

Growth,Nutrient Uptake,and Use Efficiency in Dry Bean in Tropical Upland Soil

Dry bean (Phaseolus vulgaris L., cv. ‘BRS Requinte’) is an important legume crop and nutrient availability is one of the most yields limiting factors for bean production in tropical upland soils. A greenhouse experiment was conducted in Brazilian Oxisol to study growth, nutrient uptake, and use efficiency of macro- and micronutrients during growth cycle of bean plant. Plants were harvested at 15, 30, 45, 60, 73, and 99 days after sowing for determination of growth parameters and uptake of nutrients. Root dry weight, shoot dry weight and leaf trifoliate increased significantly (P< 0.01) in a quadratic fashion with the advancement of plant age. However, root-shoot ratio decreased significantly with increasing plant age. Concentrations of nitrogen (N), calcium (Ca), magnesium (Mg), and zinc (Zn) decreased with the advancement of plant age. However, concentrations of phosphorus (P), potassium (K), copper (Cu), and manganese (Mn) increased significantly with the advancement of plant age. Accumulation of macro- and micronutrients significantly increased with the increasing plant age. Accumulation of N, P, K and Cu was higher in the grain compared with root and shoot, indicating relatively higher importance of these nutrients in improving grain yield of dry bean. Nitrogen, P and Cu use efficiency was higher for shoot weight compared to grain weight. For grain production, nutrient use efficiency was in the order of Mg > Ca > P > K > N for macronutrients and Cu > Zn = Mn for micronutrients.     

Agronomic assessment of phosphorus efficacy for potato (Solanum tuberosum L) under legume intercrops

Abstract

Phosphorus (P) is an essential element and its efficient use is of global importance. This study evaluated the effect of growing potato under legume intercrops on P uptake and use efficiency indices: P harvest index (PHI), P uptake efficiency (PuPE), P partial factor productivity (PPFP) and P partial balance (PPB). The experiment was carried out for four consecutive seasons with treatments comprising potato cultivated under legume intercrops: none (T1), dolichos (Lablab purpureus L) (T2), peas (Pisum sativum L) (T3) and beans (Phaseolus vulgaris L) (T4). Across the seasons, the mean haulm P uptake for T2 (6.7?kg P ha^?1), T4 (5.5) and T3 (4.5) were 6%, 23% and 36% lower than that observed in T1 (7.1?kg P ha^?1), respectively. On the other hand, tuber P uptake was highest in T1 (21.8?kg P ha^?1) and T2 (21.3?kg P ha^?1) and were significantly higher than 13.2?kg P ha^?1 in T3 and 15.1?kg P ha^?1 in T4. This had a profound effect on PuPE, which was equally highest in T1 (0.26?kg total P uptake kg^?1 P supply) and T2 (0.25) and lowest in T3 (0.16) and T4 (0.18). Similarly, PPFP, PHI and PPB followed a similar trend, with highest values in T1 (57?kg tuber dry matter yield kg^?1 P supply, 76.4?kg tuber P uptake kg^?1 total plant’s P uptake and 0.20?kg tuber P uptake kg^?1 P supply, respectively). Among the tested legume intercrops, dolichos competed least for P with the main crop (potato) hence it can be integrated into potato-based cropping systems without compromising potato tuber yield.     

Soil Phosphorous Influence on Growth and Nutrition of Tropical Legume Cover Crops in Acidic Soil

In tropical regions, use of cover crops in crop production is an important strategy in maintaining sustainability of cropping systems. Phosphorus (P) deficiency in tropical soils is one of the most yield-limiting factors for successful production of cover crops. A greenhouse experiment was conducted to evaluate influence of P on growth and nutrient uptake in 14 tropical cover crops. The soil used in the experiment was an Oxisol, and P levels used were low (0 mg P kg^?1), medium (100 mg P kg^?1) and high (200 mg P kg^?1). There was a significant influence of P and cover crop treatments on plant growth parameters. Phosphorus X cover crops interaction for shoot dry weight, root dry weight and root length was significant, indicating different responses of cover crops to variable P levels. Based on shoot dry weight efficiency index (SDEI), legume species were classified into efficient, moderately efficient or inefficient groups. Overall, white jack bean, gray mucuna bean, mucuna bean ana and black mucuna bean were most P efficient. Remaining species were inefficient in P utilization. Macro- and micronutrient concentrations (content per unit dry weight of tops) as well as uptakes (concentration x dry weight of tops) were significantly (P < 0.01) influenced by P as well as crop species treatments, except magnesium (Mg) and zinc (Zn) concentrations. The P x crop species interactions were significant for concentration and uptake of all the macro and micronutrients analyzed in the plant tissues, indicating concentrations and uptake of some nutrients increased while others decreased with increasing P levels. Hence, there was an antagonistic as well as synergetic effect of P on uptake of nutrients. However, uptake of all the macro and micronutrients increased with increasing P levels, indicating increase in dry weight of crop species with increasing P levels. Overall, nutrient concentration and uptake in the top of crop species were in the order of nitrogen (N) > potassium (K) > calcium (Ca) > Mg > sulfur (S) > P for macronutrients and iron (Fe) > manganese (Mn) > zinc (Zn) > copper (Cu) for micronutrients. Interspecific differences in shoot and root growth and nutrient uptake were observed at varying soil P levels     

Residual Effect of Phosphorus Fertilizer in a Low‐Humic Andosol with Low Extractable Phosphorus

Abstract

Phosphorus (P) fertilization is quite important for crop production grown on Andosols. Fertilizer P‐use efficiency was 17% in a long‐term wheat experiment on a low‐humic Andosol. Residual effects of P fertilization were investigated using field soils in pot experiments. Topsoil was collected from the plots with or without annual P fertilizer at the rate of 65 kg‐P ha^?1 for 23 years (nitrogen phosphorous potassium (NPK) soil and nitrogen potassium (NK) soil, respectively). There was no significant difference in dry matter of wheat and P uptake between NPK and NK soils. However, dry matter of rice and P uptake were higher in NPK soil than in NK soil. Inorganic aluminum P (Al‐P_i) and iron P (Fe‐P_i) increased in NPK soil. Increase in Al‐P_i and Fe‐P_i during 23 years contributed little to P uptake by wheat, and repeated P fertilization is indispensable to obtain acceptable grain yield.     

NITROGEN USE EFFICIENCY IN DRY BEAN GENOTYPES

Dry bean is an important legume crop for Latin American people and nitrogen is one of the most yields limiting nutrients for bean crop. A greenhouse experiment was conducted to evaluate nitrogen (N) use efficiency of 20 dry bean genotypes. Genotypes were grown on an Oxisol and two N levels used were without N application (low level) and an application of 400 mg N kg^?1 (high level). Shoot dry weight, grain yield and yield components, N concentration and uptake in shoot and grain were significantly affected by N and genotype treatments. Grain yield had a highly significant (P < 0.01) association with shoot dry weight, pod number, grains per pod and 100 grain weight. Among the 20 genotypes tested, Perola, CNFR 7847, CNFR 7865, CNFP 7777 and CNFM 6911 were found to produce reasonably good yield at low N rate as well as responded well to applied N. Whereas, some genotypes like BRS Radiante, CNFP 7624, CNFM 7875, CNFM 7886, CNFC 7813, CNFC 7827, CNFP 7677 and CNFP 7775 produced very good yields at higher N rate but very low yields at lower N rate. Hence, these genotypes are good for farmers using higher technology. Nitrogen concentration and uptake were higher in dry bean grains compared with shoot and 63% of N accumulated at zero N rate and 75% N accumulated at 400 mg N rate were translocated to grain across 20 genotypes. Nitrogen uptake efficiencies were having highly significant (P < 0.01) quadratic relationship with grain yield. This indicates that improving N uptake in dry bean plants can increase grain yield.     

UPLAND RICE GENOTYPES EVALUATION FOR PHOSPHORUS USE EFFICIENCY

Phosphorus (P) deficiency is one of the most yield limiting factors in crop production in Brazilian Oxisols. A greenhouse experiment was conducted to evaluate 20 upland rice genotypes at low (25 mg P kg^?1) and high (200 mg P kg^?1) P levels applied to a Brazilian Oxisol. Grain yield and yield components were significantly influenced by P level and genotype treatments. There was a significant interaction between P level and genotype treatments in relation to grain yield, indicating genotypes responded differently under two P levels. Based on grain yield efficiency index (GYEI), genotypes were classified into efficient, moderately efficient and inefficient groups. The efficient genotypes in utilizing P were ‘BRA052053’, ‘BRS Primavera’, ‘BRA052015’, ‘BRA052023’, ‘BRA01506’, ‘BRA052045’, ‘BRA032033’, ‘BRA01596’ and ‘BRA052034’. Remaining genotypes were classified as moderately efficient in P use efficiency. None of the genotypes were fall into inefficient group. Grain yield was significantly and positively related with shoot dry weight, panicle number, grain harvest index, 1000-grain weight and had a negative and significant correlation with spikelet sterility. Grain weight was having maximum contribution in total rice plant weight comparing to root and shoot, indicating improvement in harvest index of modern Brazilian upland rice cultivars by breeding.     

Organic amendments as a source of phosphorus: agronomic and environmental impact of different animal manures applied to an acid soil

Phosphorus (P) is a non-renewable resource highlighting the significance of developing and using alternative P sources for a sustainable agriculture. The work aims to compare the effects of different organic amendments (OA) and a mineral P fertiliser as reference on P use efficiency by the crop, and on P losses to runoff waters and eroded sediments. A two-year field trial was conducted in a Dystric Regosol with Lolium sp. Treatments were: cattle manure compost (CM), solid fraction of swine (SS) and duck (DS) slurries and triple superphosphate (TSP), each applied at 50 kg P ha^?1 year^?1. Olsen P (mg P kg^?1) increased from ≈ 19 at the beginning to ≈ 30 (TSP, CM), 45 (SS) and 62 (DS) after the experiment. Most of applied P remained in soil, between 92% (SS) and 96% (TSP), plant uptake ranged from 5% (CM) to 3.5% (TSP) and total P loss in runoff and sediments ranged between 0.2% (CM) and 4% (SS). OA increased P-use efficiency by the ryegrass crop compared with mineral P fertilizer. Composted cattle manure showed the best agronomic and environmental behaviour, simultaneously increasing P-use efficiency and decreasing P losses by runoff and erosion.     

Yield and Yield Components and Phosphorus Use Efficiency of Lowland Rice Genotypes

Phosphorus deficiency is main constraints for lowland rice production in various rice producing regions of the world. A greenhouse experiment was conducted using lowland (Inceptisol) soil with the objective to determine response of seven lowland rice (Oryza sativa L.) genotypes to phosphorus fertilization and to evaluate their phosphorus (P) use efficiency. Phosphorus treatments included control (0 mg P kg^?1) and 200 mg P kg^?1 of soil. Plant height and shoot dry weight were significantly (P < 0.001) influenced by P treatments. Phosphorus X genotypes interaction was significant for shoot dry weight, indicating different response of genotypes under two P levels. At low P level, none of the genotypes produced grain yield, indicating original P level in the soil was too low for lowland rice yield. However, genotypes differed significantly in grain yield at high P level. Panicle number, panicle length, and thousand grains weight had a significant quadratic association with grain yield. However, spikelet sterility had a significant linear negative association with grain yield. The P use efficiency expressed as agronomic efficiency (AE), physiological efficiency (PE), agro-physiological efficiency (AP), apparent recovery efficiency (ARE), and utilization (UE) were significantly different among genotypes. These efficiencies were having significantly positive association with grain yield, with exception to ARE, indicating improving grain yield with improved P use efficiencies in rice.     

Screening Upland Rice Genotypes for Manganese‐use Efficiency

Manganese (Mn) deficiency in upland rice grown after common bean or soybean, which received adequate rate of liming on highly weathered Oxisols, is observed. A greenhouse experiment was conducted to evaluate Mn‐use efficiency of 10 promising upland rice genotypes. The genotypes were grown on an Oxisol at 0 mg Mn kg^?1 (natural soil Mn level) and 20 mg Mn kg^?1 of soil applied as manganese sulfate. Grain yield, panicle number, and grain harvest index (GHI) were significantly (P < 0.01) influenced by genotype. However, shoot dry weight was significantly affected by Mn as well as genotype treatments. Manganese uptake in the shoot as well as in the grain was also affected by genotype treatment. On the basis of Mn‐use efficiency (mg grain weight/mg Mn accumulated in shoot and grain), genotypes were classified as efficient and responsive (ER), efficient and nonresponsive (ENR), nonefficient and responsive (NER), and nonefficient and nonresponsive (NENR). Genotypes Carisma, CNA8540, and IR42 were classified as ER, and genotypes CNA8557 and Maravilha were classified as ENR. Genotype Caipo was in the group NER, and in the NENR group were genotypes Bonança, Canastra, Caraja, and Guarani. From a practical point of view, genotypes that produce high grain yield at a low level of Mn and respond well to Mn additions are the most desirable because they are able to express their high yield potential in a wide range of Mn availability.     

Comparison of Mehlich-3 and Ammonium Bicarbonate-DTPA for the Extraction of Phosphorus and Potassium in Calcareous Soils from Florida

Developing a fast and reliable soil testing method is critical for improving soil testing efficiency and ensuring reliable fertilizer recommendation. The objectives of this study were to evaluate Mehlich-3 (M-3) as a replacement for ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA) to extract phosphorus (P) and potassium (K) and to determinate the relationships between extractable P and K and their uptakes by crop in calcareous soils. M-3 and AB-DTPA were compared by using two approaches. In the first approach, the amounts of extracted P and K were compared by analyzing soil samples collected from agricultural production areas; in the second approach, snap beans (Phaseolus vulgaris) were grown in pot to determine the P and K uptakes by crop. There were significant correlations between M-3 and AB-DTPA for both soil test P and K based on soils collected from the agricultural field and the pot study. Soil test P and K by both extractants were significantly correlated with their uptakes by snap bean. The critical value of M-3-P regarding snap bean uptake was 47 mg kg^?1 and was higher than that (18 mg kg^?1) for AB-DTPA-P, whereas critical soil test K levels were similar between M-3 and AB-DTPA. M-3 was identified as an alternate improved extraction method instead of AB-DTPA in calcareous soils based on this study. However, more work will be needed to identify the correlation of the two extractants and crop responses under a field condition.     

Phytoremediation of High-Phosphorus Soil by Annual Ryegrass and Common Bermudagrass Harvest

Removal of soil phosphorus (P) in crop harvest is a remediation option for soils high in P. This 4-year field-plot study determined P uptake by annual ryegrass (ARG, Lolium multiflorum Lam.) and common bermudagrass (CB, Cynodon dactylon (L.) Pers.) from Ruston soil (fine-loamy, siliceous, thermic Typic Paleudult) enriched in P by five previous annual applications of poultry litter, and related P removed to Bray 2 P in surface (0–15 cm) soil. Decreases in surface soil Bray 2 P were largely attributable to uptake. Phosphorus uptake was positively related to Bray 2 P but approached a limit. Mass of P removed in harvest closely approximated the decrease in mass of surface soil Bray 2 P. Maximum Bray 2 P drawdown per harvest (ARG and CB, average) was ?3 mg kg^?1 at Bray 2 P ? 300 mg kg^?1, generally consistent with measured decreases in Bray 2 P.     

Differential Growth Performance of 15 Wheat Genotypes for Grain Yield and Phosphorus Uptake on a Low Phosphorus Soil Without and With Applied Phosphorus Fertilizer

ABSTRACT

Two field experiments were conducted to compare 15 wheat genotypes at two phosphorus (P) levels (zero-P control or low P level—without application of P fertilizer on soil with 8 mg extractable P kg^?1, and adequate P level—with P fertilizer applied at 52 kg P ha^?1) for yield, P uptake, and P utilization efficiency (P efficiency ratio—PER, P harvest index—PHI, and P physiological efficiency index—PPEI). On the average of two experiments, substantial and significant differences were observed among wheat genotypes for both grain and straw yields at both P levels. Grain yields ranged from 2636 to 4455 kg ha^?1 in the zero-P control, and from 2915 to 4753 kg ha^?1 at adequate P level. Genotype 5039 produced the maximum grain yield, while 6529-11 had the minimum grain yield at both P levels. Relative reduction in grain yield due to P deficiency stress (PSF) ranged from none to 32%, indicating differential P requirements of genotypes. Genotypes 4943, Pasban 90, Inqlab 91, PB 85, Lu 26s, 4770, Chakwal 86, 4072, 6544-6, and 5039 had little or no response to P application. Phosphorus responsive genotypes included FSD 83, Kohinoor 83, Parvaz-94, Pak 81, and 6529-11. A non-significant correlation (r = ?0.466, P > 0.05) between grain and PSF in zero-P control treatment also indicated the least effect of P deficiency on some wheat genotypes. A wide range of PPEI (270–380 kg grain kg^?1 P absorbed in grain + straw at control P level, and 210–330 kg grain kg^?1 P absorbed in grain + straw at adequate P level) indicated differential utilization of absorbed P by the genotypes for grain production. This indicated that wheat genotypes differed considerably in their P requirement for growth and responsiveness to P application. The findings also suggested that PPEI was a better parameter for measuring P efficiency than other parameters, and can be used for selecting P efficient genotypes, because it relates to the internal concentration of a nutrient and genetic makeup of plant. It is concluded that genotypes having ability to produce relatively high grain yield, good command to tune P within plant and high PPEI are suited to low P soil conditions. Genotypes 4072, Inqlab 91, 4943, Pak 81 and 5039 were P efficient and had above mentioned abilities, while genotypes FSD 83, 6544-6, and 6529-11 were P inefficient. It should be noted that traits related to P efficiency are inheritable and can be used to improve P use efficiency of a genotype through back cross breeding programs.     

Nutrient Uptake in Dry Bean Genotypes

Dry bean is an important legume for human consumption in South America. A greenhouse experiment was conducted to evaluate uptake and use efficiency of macro- and micronutrients by six dry bean genotypes at two P levels (25 and 200 mg kg^?1 soil). Shoot dry weight and grain yield varied significantly among genotypes and significantly increased with increasing phosphorus (P) levels. Grain harvest index (GHI) and 100-grain weight also differ significantly among genotypes and significantly increased with the increasing P levels. Based on grain yield efficiency index (GYEI), genotypes were classified as efficient and inefficient. The most efficient genotype was CNFP 10104, and inefficient genotypes were CNFP 10103 and CNFP 10120. Number of pods per plant and number of seeds per pod increased significantly with the addition of 200 mg P kg^?1 of soil compared to the low level of P (25 mg P kg^?1). Similarly, nitrogen (N), P, calcium (Ca), magnesium (Mg), sulfur (S), zinc (Zn), copper (Cu), and manganese (Mn) concentrations and uptake in the shoot and grain also significantly varied among genotypes. Uptake of macro- and micronutrients was greater under the greater P rate compared to the low P rate. This may be related to greater shoot or grain yield at 200 mg P kg^?1 soil compared to 25 mg P kg^?1 of soil.     

Rice Yields Enhanced through Integrated Management of Cover Crops and Phosphate Rock in Phosphorus‐deficient Ultisols in West Africa

The relatively low solubility and availability of phosphorus (P) from indigenous phosphate rock could be enhanced by legumes in the acid soils of humid forest agroecosystems. Crotalaria micans L. was grown in a screenhouse without P or with P from triple superphosphate (TSP) and Malian Tilemsi Rock P. The P response of 20 cover crops was field‐evaluated using TSP and Rock P. In both experiments, the fertilized cover crops were followed by upland rice without mineral N or P application. Mean rice grain yield and agronomic residual P‐use efficiency were similar for both P sources. In the field, 1‐year fallow treatment of Canavalia ensiformis (velvet bean) supplied with Mali Rock P gave the highest rice grain yield of 3.1 Mg ha^?1, more than 180% that of 2‐year continuous unfertilized rice (cv. ‘WAB 56‐50’). Among continuous rice plots, ‘NERICA 2’ (interspecific rice) supplied with Rock P produced the highest yield (2.0 Mg ha^?1), suggesting that ‘NERICA 2’ might have greater potential to solubilize rock P. Results indicate that when combined with an appropriate legume, indigenous rock‐P can release sufficient P to meet the P requirement of the legume and a following upland rice crop in rotation.     

Variation in Yield,Phosphorus Uptake,and Physiological Efficiency of Wheat Genotypes at Adequate and Stress Phosphorus Levels in Soil

Genetic differences among crop genotypes can be exploited for identification of genotypes more suited to a low‐input agricultural system. Twenty wheat (Triticum aestivum L.) genotypes were evaluated for their differential yield response, phosphorus (P) uptake in grain and straw, and P‐use efficiency at the zero‐P control and 52 kg P ha^?1 rates. Substantial and significant differences were obvious among genotypes for both grain and straw yields at stress (8 mg P kg^?1 soil, native soil P, no P addition) and adequate (52 kg P ha^?1) P levels. Genotype 5039 produced maximum grain yield at both P levels. Relative reduction in grain yield due to P‐deficiency stress [i.e., P stress factor (PSF)] ranged between none and 32.4%, indicating differential P requirement of these genotypes. Pasban 90, Pitic 62, Rohtas 90, Punjab 85, and line 4943 did not respond to P application and exhibited high relative yield compared to those at adequate P level. FSD 83 exhibited the best response to P with maximum value for PSF (32.4%). Genotypes were distributed into nine groups on the basis of relationship between grain yield and total P uptake. Rohtas 90 and lines 4072 and 5039 exhibited high grain yield and medium P uptake (HGY‐MP). However, line 5039 with high total index score utilized less P (12.2 kg P ha^?1) than line 4072 and Rohtas 90 (13.5 and 13.6 kg P ha^?1, respectively). Moreover, this genotype also had greater P harvest index (PHI, %) and P physiological efficiency index (PPEI) at stress P level. Pasban 90, Pitic 62, and Pak 81 had the greatest total index score (21), mainly due to high total P uptake, but yielded less grain than lines 5039 and 4072 under low available P conditions. Line 6142 had minimum total index score (15) and also produced minimum grain yield. A wide range of significant differences in PPEI (211 to 365 kg grain kg^?1 P absorbed at stress and 206 to 325 kg grain kg^?1 P absorbed by aboveground plant material at adequate P) indicated differential utilization of absorbed P by these genotypes for grain production at both P levels. It is concluded from the results that wheat genotypes differed considerably in terms of their P requirements for growth and response to P application. The findings suggest that PSF, PHI, and PPEI parameters could be useful to determine P‐deficiency stress tolerance in wheat.     

Eucalyptus biochar application enhances Ca uptake of upland rice,soil available P,exchangeable K,yield, and N use efficiency of sugarcane in a crop rotation system

It was hypothesized that the application of eucalyptus biochar enhances nutrient use efficiencies of simultaneously supplied fertilizer, as well as provides additional nutrients (i.e., Ca, P, and K), to support crop performance and residual effects on subsequent crops in a degraded sandy soil. To test this hypothesis, we conducted an on‐farm field experiment in the Khon Kaen province of Northeastern Thailand to assess the effects of different application rates of eucalyptus biochar in combination with mineral fertilizers to upland rice and a succeeding crop of sugarcane on a sandy soil. The field experiment consisted of three treatments: (1) no biochar; (2) 3.1 Mg ha^?1 biochar (10.4 kg N ha^?1, 3.1 kg P ha^?1, 11.0 kg K ha^?1, and 17.7 kg Ca ha^?1); (3) 6.2 Mg ha^?1 biochar (20.8 kg N ha^?1, 6.2 kg P ha^?1, 22.0 kg K ha^?1, and 35.4 kg Ca ha^?1). All treatments received the same recommended fertilizer rate (32 kg N ha^?1, 14 kg P ha^?1, and 16 kg K ha^?1 for upland rice; 119 kg N ha^?1, 21 kg P ha^?1, and 39 kg K ha^?1 for sugarcane). At crop harvests, yield and nutrient contents and nitrogen (N) use efficiency were determined, and soil chemical properties and pH₀ monitored. The eucalyptus biochar material increased soil Ca availability (117 ± 28 and 116 ± 7 mg kg^?1 with 3.1 and 6.2 Mg ha^?1 biochar application, respectively) compared to 71 ± 13 mg kg^?1 without biochar application, thus promoting Ca uptake and total plant biomass in upland rice. Moreover, the higher rate of eucalyptus biochar improved CEC, organic matter, available P, and exchangeable K at succeeding sugarcane harvest. Additionally, 6.2 Mg ha^?1 biochar significantly increased sugarcane yield (41%) and N uptake (70%), thus enhancing N use efficiency (118%) by higher P (96%) and K (128%) uptake, although the sugar content was not increased. Hence, the application rate of 6.2 Mg ha^?1 eucalyptus biochar could become a potential practice to enhance not only the nutrient status of crops and soils, but also crop productivity within an upland rice–sugarcane rotation system established on tropical low fertility sandy soils.