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Phosphorus and zinc are important nutrient elements of concern in upland rice production. To determine the suitable combination of phosphorus, nanoparticles (NPs), and bio-fertilizer application as an alternative nutrient management approach in upland rice cultivation, a Polyvinyl Chloride (PVC) column experiment was conducted under controlled conditions in 2015. The treatments consisted of three phosphorus levels, two foliar sprays of NPs (ZnO and TiO2), and PSB seed treatment. The results indicated that the combined application of P (50 kg ha−1), ZnO NPs (500 ppm), and PSB seed treatment (20 g kg−1) improved the root system architecture traits of rice (total root length: 3.73–6.74%, diameter: 8.57–22.22%, and volume: 3.40–3.70%) at depths of 0–30 cm and 30–60 cm, compared to higher P + TiO2 NPs + no PSB. Consequently, this combination led to an enhancement in photosynthetic leaf area (by 3.3%), tiller numbers (by 7%), and dry matter production (by 35.5%). The favorable root growth resulting from the application of higher P and PSB enhanced zinc uptake by rice grains (by 38.44%) and straw (by 26.99%). Furthermore, the supplemental application of PSB improved the activity of soil enzymes such as dehydrogenase and phosphatase. As a result, maximum phosphorus use efficiency (PUE; 31.5%) was achieved through the combined application of P (50 kg ha−1) × ZnO NPs × PSB. In conclusion, this study demonstrated the beneficial effects of an integrated approach involving phosphorus, PSB, and metal oxides (ZnO NPs) as a fertilizer management strategy to enhance the total biomass and PUE of upland rice. [ABSTRACT FROM AUTHOR]

To clarify the effects of mechanically dry direct-seeded rice (MD-DSR) through drilling and controlled-release compound fertilizer (CRF) on rice production, field experiments were carried out with mixed controlled-release urea; controlled-release potassium; and common urea, phosphorus and potash fertilizers as test materials. The experiment was implemented with a split-plot design, with fertilization modes as the main plots and two varieties (indica and japonica) as the subplots. The fertilization modes were a one-time application of CRF (denoted Indica and Japonica when applied to indica and japonica, respectively), a basal application of CRF followed by topdressing with urea at the tillering stage (Indica + N, Japonica + N) and three-time fertilization, representing typical farmer fertilization practices (FFP) (Indica + FFP, Japonica + FFP). The results showed that the yields of indica and japonica rice were 5.5–15.8% and 5.3–16.3% higher, respectively, under the two CRF treatments than under FFP in the 3 years of the experiment. The effective tiller percentage, shoot and root biomass, root-shoot ratio, and harvest index of the population and the biomass per plant of indica and japonica rice improved under the two CRF treatments relative to FFP. The Indica + FFP and Japonica + FFP plants exhibited higher total N accumulation but significantly lower fertilizer partial productivity than the corresponding plants under the two CRF treatments. The net benefits to indica and japonica under the two CRF treatments were higher than those under FFP. Therefore, MD-DSR combined with the one-time application of CRF can increase rice yield, reduce fertilizer and labor costs, and benefit rice production. [ABSTRACT FROM AUTHOR]

Rice (Oryza sativa L.) is one of the most produced cereals in the world. Among the essential nutrients required by this crop, nitrogen (N) is of paramount importance to achieve optimum yields. In paddy fields, ammonium (NH4+) represents the main source of N. This work aimed to evaluate the root morphology, ammonium uptake kinetics and N accumulation in two upland rice varieties, Piauí and Manteiga from Maranhão – Brazil. The varieties were cultivated in hydroponic conditions and submitted to three different doses of ammonium: 1 – constant treatment with 0.2 mM NH4+, 2 – constant treatment with 1 mM NH4+ and 3 – constant treatment with 1 mM NH4+, followed by N starvation during 72 h and resupply with 1 mM NH4+. The varieties present contrasting behaviors when submitted to different doses of NH4+. Piauí showed higher biomass and root length under the treatment with 0.2 mM NH4+. The favorable kinetics parameters observed contributed to a higher N accumulation by Piauí in low dose of NH4+. Under 1 mM NH4+, a higher root biomass and favorable kinetics parameters was recorded by Manteiga. This variety presented a better performance with higher doses of N. Under the treatment of N resupply, Piauí variety showed to be more adapted, due to the greater root plasticity observed. For one hand, the results suggest that Piauí variety presents greater growth in environments with low dose or seasonal flux of NH4+. On the other hand, Manteiga variety presents better growth when submitted to higher levels of NH4+. [ABSTRACT FROM AUTHOR]

Continuous cultivation of dry seeded rice in addition to adverse environmental factors make the rice soils deficient of nitrogen more than any other essential nutrient. The study was conducted under greenhouse conditions in pots by varying soil N during seedling growth. Six cultivars with diverse genetic background, CL152, R4100412, Antonio, Bowman, Nipponbare, and Rex, were seeded in 6 × 12 inch PVC pots filled with 3:1 (sand: soil) as the rooting medium. All plants were irrigated with full-strength Hoagland nutrient solution, delivered three times for 28 days after sowing. Then, half the plants in each cultivar were supplied with 100% of control nutrient solution minus N for another 4 weeks. Agronomic, physiological and root parameters measurements recorded at optimum interval. Cumulative indices were calculated by summing each response index value as a ratio of treatment by control values. Cultivars were classified based on total cumulative N stress response index (TCNSRI), the sum of all the traits measured, into different groups based on mean and standard error. The reductions in most of the measured traits were less in CL152 and R4100412 than other rice cultivars to soil N stress. Based on total cumulative N stress response indices, the cultivars were classified. The cultivar R41004122 was identified as tolerant, CL152 as intermediate, and Antonio, Bowman, Nipponbare and Rex were sensitive to soil N stress. The identified soil N stress tolerant and intermediately tolerant cultivars will be useful to breeders to develop new genotypes and farmers to select cultivars best suited for dry seeded rice. [ABSTRACT FROM AUTHOR]

A possible way to improve phosphate rock (PR) agronomic performance is through the addition of elemental sulfur (S0). We used 32P isotope dilution method to assess the P taken up by crops treated with PR. Two experiments, one with common bean and other with upland rice, were carried out, to evaluate the effect of S0 on the agronomic performance of two contrasting PR, applied in different methods. Gafsa (GPR) and Patos de Minas (PPR) were used as the high and low reactivity PR, respectively. The experiments were arranged in completely randomized design on factorial structure 2 × 2 × 2 + 2; which means 2 PR (GPR and PPR) versus 2 S0 condition (with or without-S0) versus 2 application methods (band and broadcast) plus 2 additional treatments (control and triple superphosphate). In band application the S0 increased the amount of P uptake by plants from fertilizer of GPR from 2.57 to 9.86 mg pot−1 for common bean and of 2.26 to 7.05 mg pot−1 to rice. Regardless the management adopted, less than 2% of P applied as PPR has been taken up by crops. The addition of S0 as a strategy to increase the agronomic performance of PR is PR characteristics dependent and fertilizers placement. [ABSTRACT FROM AUTHOR]

Two field experiments were carried out separately to evaluate the ability of three plant growth promoting microorganisms (PGPM, Pantoea ananatis, Enterobacter sp. and Piriformospora indica) as bio-fertilizer on rice (Oryza sativa L.) productivity under different levels of potassium sulfate fertilizer (PSF). The results clearly showed that the PGPM significantly enhance the dry weight of rice plant tissues as compared with the control. Uptake of phosphorus and potassium in rice plant tissues and also nutrient use efficiency (NUE) remarkably increased especially when the co-inoculation with P. ananatis and P. indica in experiment I and the combined (seed + seedling root) inoculation method in experiment II were used. Grain yield (GY) increased linearly with the addition of PSF up to 110 kg ha−1 for the co-inoculation treatment (23% lower than the control), then remained constant at its maximum (5348 kg ha−1, 32% higher than the control) up to 180 kg ha−1 in experiment I. Similarly, the maximum value of GY (5330 kg ha−1, 20% more than the control) was obtained at 100 kg ha−1 PSF in experiment II. Consequently, both co-inoculation and combined inoculation methods could be selected as the best ways for improving NUE and plant growth of rice in sustainable production systems. [ABSTRACT FROM AUTHOR]

The present study investigated how foliar zinc (Zn) application affects seedling growth and Zn concentration of rice grown in a Zn-deficient calcareous soil with different soil Zn treatments. Seeds were sown in soil with five rates of Zn (0, 0.02, 0.1, 0.5 and 5.0 mg kg−1 soil) with and without foliar application of 0.5% ZnSO4. Seedlings were harvested at 35 days and separated into (i) the youngest leaves, (ii) the remaining shoot parts and (iii) roots. In soil with no Zn supply, shoot and root dry weight of the rice seedlings were significantly increased by foliar and soil Zn treatments. Plant growth was not clearly increased in low soil Zn treatments, while at each soil Zn treatment, foliar Zn application promoted growth of plants. Plants with adequate Zn supply had the highest Zn concentrations in the youngest leaf. Foliar Zn spray improved Zn concentration of the new growth formed after foliar spraying which shows that Zn is phloem mobile and moved from treated leaves into youngest new leaves. The results indicate clearly in rice seedlings that shoot growth shows more responsive to low Zn than the root growth. The results obtained in the present study are of great interest for proper rice growth in Zn-deficient calcareous soils but needs to be confirmed in other rice genotypes. [ABSTRACT FROM AUTHOR]

Iron deficiency is a major production constraint of upland rice in the tropics despite is abundance in the soil. This investigation aimed to explicate the effect of iron deficiency on the growth, development, grain yield and its attributes of some selected upland rice in the rainforest. Field experiments were established at Africa Rice sub-Station, Ibadan, Nigeria. The treatments consisted of 35 upland rice genotypes and availability of iron in the soil (Fe-sufficient and Fe-deficient). The treatments were arranged in alpha lattice design with three replications. It was observed that upland rice sown in iron (Fe) deficient soils had significantly lower growth (plant height, number of tillers and seedling vigor), flowered later, with significantly lower yield attributes (1000 grain weight, filled grain) and grain yield than those sown in Fe-sufficient soils. Conversely, the number of unfilled grains were significantly higher in upland rice sown in Fe-deficient than those in sufficient soils. Percentage yield loss was in the range 98.00% to 22.95% for China best and Faro 65 respectively. Genotypes were identified to be tolerant (Faro 65, NERICA 3 and IRAT 109) and susceptible (Ofada 2, NERICA 5 and China Best) to Fe-deficiency based on their percentage grain yield loss. These evidences suggested that despite the increased phenology of upland rice sown in Fe-deficient soils their reproductive growth was suppressed through increased number of unfilled grains as witnessed in China Best and Faro 64. [ABSTRACT FROM AUTHOR]

To optimize the nutrient management of upland rice production on tropical ferralsols, a greenhouse experiment was established using the multi-nutrient omission approach. A reciprocal soil origin-rice cultivar transplant experiment was also conducted to better understand the relative contributions of the soil origin and the rice cultivar in rice nutrient limitation. We tested the deficiency of seven major and secondary nutrients [nitrogen (N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca), magnesium (Mg), and silicon (Si)] and a solution of six micronutrients (B, Mn, Cu, Co, Na, Mo) likely to limit the growth of two upland rice cultivars, Chhomrong Dan and Nerica 4, on two Ferralsols from the highlands of Madagascar. We found severe multiple nutrient deficiencies. For both cultivars, P, Ca, N, Mg omission significantly depressed the shoot and root dry biomass and their amounts in plant tissues. However, the main limiting nutrients were not the same in both soils. We conclude that the multinutrient deficiencies observed for rice growth in the Ferralsols are site-specific, even though P limitation appears to be in common, and requires a holistic consideration of the mineral fertility, including micronutrients. [ABSTRACT FROM AUTHOR]

Differences among rice genotypes demonstrate that root system of upland rice cultivars influences P acquisition and growth performance. We studied root and shoot growth and nutrition of traditional and modern cultivars of upland rice as affected by P availability (three rates). At the highest P rate, the greatest dry mass was obtained with Maravilha, which was on average 180% higher than Caiapo. The modern has exceeded the traditional in growth performance, besides accumulating more nutrients. Maravilha was more efficient in root and shoot growth, and nutrient absorption with P supply, using less photoassimilates for root growth. Traditional cultivars of upland rice may develop better than modern cultivars in low P availability, with facilitates its adaptation in soils with this condition. Modern cultivars are more responsive to P fertilization, which demonstrates a better option in a cropping system with P supply to aim at high yield. [ABSTRACT FROM AUTHOR]

Deficiency of micronutrients increasing in field crops, including upland rice in recent years. The objective of this study was to determine requirement of zinc (Zn), copper (Cu) boron (B) and iron (Fe) for upland rice grown on a Brazilian Oxisol. The levels used were: Zn (0, 10, 20, 40, and 80 mg kg−1), Cu (0, 5, 10, 20 and 40 mg kg−1), B (0, 5, 10, 20 and 40 mg kg−1) and Fe (0, 250, 500, 1000, and 2000 mg kg−1). Plant height, straw yield, grain yield, panicle number and grain harvest index (GHI) were significantly improved with the addition of these micronutrients. Root growth was also improved with the application of micronutrients, except with the addition of B. Maximum grain yield was obtained with the addition of 51 mg Zn, 24 mg Cu, 5 mg B kg−1, and 283 mg Fe kg−1soil. Similarly, maximum straw yield was obtained with the addition of 38 mg Zn, 17 mg Cu, 6 mg B kg−1, and 1500 mg Fe kg−1soil. Maximum plant height was obtained with the addition of 54 mg Zn, 10 mg B kg−1, and 1197 mg Fe kg−1soil. Copper did not affect plant height significantly. Maximum panicle number was obtained with the addition of 22 mg Cu kg−1, 3 mg B kg−1, and 1100 mg Fe kg−1soil. Zinc did not affect panicle number significantly. Maximum GHI was obtained with the addition of 61 mg Zn kg−1, and 8 mg B kg−1. Zinc was had a linear increase in GHI in the range of 0 to 80 mg kg−1, and Fe showed a negative relationship with GHI. [ABSTRACT FROM PUBLISHER]

Upland rice is an important crop in South America, including Brazil. Nutrient interactions are important in determining crop yields. A greenhouse experiment was conducted to evaluate interaction among nitrogen (N), phosphorus (P), and potassium (K) in upland rice production. The treatments applied to upland rice grown on an Oxisol were three levels of N (N0, N150and N300mg kg−1), three levels of P (P0, P100and P200mg kg−1) and three levels of K (K0, K100and K200mg kg−1). These treatments were tested in a 3 × 3 × 3 factorial arrangement. Grain yield, shoot dry weight, plant height, root dry weight, maximum root length, panicle number, 1000-grain weight, and grain harvest index were significantly influenced by N, P, and K treatments. The treatment that did not receive P fertilization did not produce panicle or grain. Hence, P was most yield-limiting nutrient compared to two other nutrients. At the N0P0K0treatment, rice did not produce grains, indicating severe deficiency of these nutrients in Brazilian Oxisols. Maximum grain yield was obtained with the N300P200K200treatment. Grain yield had significant positive association with plant height, shoot dry weight, root dry weight, maximum root length, 1000-grain weight, panicle number, and grain harvest index. Among these growth and yield components, shoot dry weight had the highest positive association with grain yield and root length minimum positive association with grain yield. Hence, adopting adequate soil and crop management practices can improve growth and yield components and increase grain yield of upland rice. [ABSTRACT FROM AUTHOR]

Phosphorus (P) deficiency is one of the most yield limiting factors for crop production in South American soils. Upland rice (Oryza sativaL.) 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−1or 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). [ABSTRACT FROM AUTHOR]

The plant root system is an important organ which supplies water and nutrients to growing plants. Information is limited on influence of nitrogen fertilization on upland rice root growth. A greenhouse experiment was conducted to evaluate influence of nitrogen (N) fertilization on growth of root system of 20 upland rice genotypes. The N rate used was 0 mg kg−1(low) and 300 mg kg−1(high) of soil. Nitrogen X genotype interactions for root length and root dry weight were highly significant (P< 0.01), indicating that differences among genotypes were not consistent at two N rates. Overall, greater root length, root dry weight and tops-roots ration were obtained at an N fertilization rate of 300 mg kg−1compared with the 0 mg N kg−1soil. However, genotypes differ significantly in root length, root dry weight and top-root ratio. Nitrogen fertilization produced fine roots and more root hairs compared with absence of N fertilizer treatment. Based on root dry weight efficiency index (RDWEI) for N use efficiency, 70% genotypes were classified as efficient, 15% were classified as moderately efficient and 15% were classified as inefficient. Root dry weight efficiency index trait can be incorporated in upland rice for improving water and nutrient efficiency in favor of higher yields. [ABSTRACT FROM PUBLISHER]

Understanding rice phenology and nutrient uptake pattern is important for adequate crop management and improving yields. A greenhouse experiment was conducted with the objective to monitoring upland rice (cv. Talento) phenology and nutrient uptake pattern during its growth cycle. Growth observations and plant analysis were performed at initiation of tillering (IT), active tillering (AT), panicle initiation (PI), booting (B), flowering (F) and physiological maturity (PM). Shoot dry weight plus grain yield and root dry weight increased significantly (P < 0.01) with age and followed exponential cubic responses. Similarly, plant height, number of tillers per plant, number of leaves on main culm and maximum root length increased significantly (P < 0.01) in quadratic fashion with increasing plant age. Concentrations of nitrogen (N), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe) and manganese (Mn) increased significantly (P < 0.01) and quadratically with plant age, whereas, phosphorus (P), copper (Cu) and zinc (Zn) decreased quadratically with increasing plant age. Uptake of macro- and micronutrients increased significantly in quadratic fashion with increasing plant age. Plant growth parameters had highly significant (P < 0.01) association with shoot dry weight plus grain yield in the order of shoot dry weight > root dry weight > plant height > root length. Similarly, uptake of macronutrients also had highly significant (P < 0.01) association with dry matter plus grain yield in the order of Ca > Mg > K > P > N, indicating deficiency of these nutrients in Brazilian Oxisols for rice production. [ABSTRACT FROM AUTHOR]

Ammonium sulfate and urea are main sources of nitrogen (N) for annual crop production in developing countries. Two greenhouse experiments were conducted using ammonium sulfate and urea as N sources for upland rice grown on a Brazilian Oxisol. The N rates used were 0, 50, 100, 150, 3000, and 400 kg N kg-1 of soil. Yield and yield components were significantly increased in a quadratic fashion with increasing N rate. Ammonium sulfate X urea interaction was significant for grain yield, shoot dry matter yield, panicle number, plant height and root dry weight, indicating a different response magnitude of these plant parameters to two sources of N. Based on regression equation, maximum grain yield was achieved with the application of 380 mg N kg-1 by ammonium sulfate and 271 mg N kg-1 by urea. Grain yield and yield components were reduced at higher rates of urea (>300 mg kg N) but these plant parameters' responses to ammonium sulfate at higher rates was constant. In the intermediate N rate range (125 to 275 mg kg-1), urea was slightly better compared to ammonium sulfate for grain yield. Grain yield was significantly related with plant height, shoot dry weight, panicle number, grain harvest index and root dry weight. Hence, improving these plant characteristics by using appropriate soil and plant management practices can improve upland rice yield. [ABSTRACT FROM AUTHOR]

Nitrogen (N) deficiency is one of the most yield-limiting nutrients in upland rice growing regions word wide. A greenhouse experiment was conducted with the objective to evaluate nineteen upland rice (Oryza sativa. L.) genotypes for N use efficiency. The soil used in the experiment was an Oxisol and two N levels used were without N application (low level) and an application of 400 mg N kg-1 of soil (high level). Grain yield and yield components and N uptake parameters were significantly affected by N and genotype treatments. Regression analysis showed that plant height, shoot dry weight, number of panicles per pot, number of grains per panicle, grain harvest index, N uptake in shoot and grain were having significant positive relation with grain yield. Nitrogen concentration of 6.4 g kg-1 in the shoot is established as deficient level and 9.5 g kg-1 as sufficient level at harvest. Agronomic efficiency of N (grain yield/unit of N applied) and N utilization efficiency (physiological efficiency X apparent recovery efficiency) were significantly different among genotypes. These two N use efficiencies were having significant quadratic relationship with grain yield. Soil pH, exchangeable soil Ca and base saturation were having significantly positive association with grain yield. However, soil extractable phosphorus (P), potassium (K), hydrogen (H+), aluminum (Al) and cation exchange capacity were having significantly negative association with grain yield. [ABSTRACT FROM AUTHOR]

The nitrogen (N) and phosphorus (P) nutrient input and output balance and utilization efficiency in the pear tree ( Pyrus pyrifolia Nakai) and upland rice ( Oryza Sativa L.) inter-cropping system and pear mono-cropping system were analyzed in this paper. Results indicated that nutrient retention in the pear tree and upland rice intercropping system was 188.93 kg ha -1 a -1 , of which 169.02 kg ha -1 a -1 was N, accounting for 89.45%; P was 19. 93kg ha -1 a -1 , or 10.55% of the total. The annual nutrient absorption of N and P in the pear tree and upland rice intercropping system were 196.46 and 25.27 kg ha -1 a -1 , respectively. The nutrient absorption amount from rice was 61.32% for N and 69.97% for P, while the pear tree accounted for 6.01% and 8.99% of total N and P absorption, respectively, in the intercropping system. Upland rice intercropped in the pear tree system increased the N and P nutrient-utilization efficiency from 24.31% and 4.06% in the pear tree mono-cropping system to 56.24% and 11.97% in the pear tree and upland rice system. [ABSTRACT FROM AUTHOR]

A greenhouse pot experiment was conducted to investigate heavy metal [copper (Cu), zinc (Zn), lead (Pb), and cadmium (Cd)] uptake by two upland rice cultivars, ‘91B3’ and ‘277’, grown in a sterilized field soil contaminated by a mixture of Cu, Zn, Pb, and Cd. Rice plants were inoculated with each of three arbuscular mycorrhizal fungi (AMF), Glomus versiforme (GV), Glomus mosseae (GM), and Glomus diaphanum (GD), or remained noninoculated (NM). Both rice cultivars could be colonized by the three AMF used in this experiment. The percentage of mycorrhizal colonization by the three AMFs on the two rice cultivars ranged from 30% to 70%. Mycorrhizal colonization of both upland rice cultivars had a large influence on plant growth by increasing the shoot and root biomass compared with non-inoculated (NM) plants. The results indicate that mycorrhiza exert some protective effects against the combined toxicity of Cu, Zn, Pb, and Cd in the contaminated soil. This conclusion is supported by the partitioning of heavy metals (HMs) in the two cultivars. In the two cultivars, colonization by AMF reduced the translocation of HMs from root to shoot (except that the colonization of AMF increased the Cu translocation of HMs in cultivar ‘277’). Immobilization of the HMs in roots can alleviate the potential toxicity to shoots induced by the mixture of Cu, Zn, Pb, and Cd. The two rice cultivars showed significant differences in uptake of Cu, Zn, Pb, and Cd when uninoculated. GM inoculation gave the most protective effects on the two cultivars under the combined soil contamination. [ABSTRACT FROM AUTHOR]

Nitrogen (N) deficiency and water stress are major abiotic constraints upon the production of upland rice (Oryza sativa L.) in tropical Asia. It is, therefore, imperative to quantify the effect of N input on yield and to identify factors affecting the variability of yield response to N under various water supply conditions in order to develop efficient methods of N and crop management. Field experiments were conducted in Bihar, India, over four years to analyze the effect of N rate with split application of soluble urea, and a N sources, split application of soluble urea, and a single application of polyolefin resin-coated controlled-release urea (PCU) on the grain yield, apparent N recovery fraction (ANR), economic N use efficiency (grain yield per N uptake or GYNUE), and root growth. The yield responded linearly to increasing N rate in split urea, but along a different slope in each year. The yield response to N rate was variable among years due to variations in ANR and GYNUE. A significant relationship between the ANR and yield gain by N application across years indicated the importance of improving ANR to maximize the cost-benefit ratio. A comparison of split urea and PCU indicated that ANR could be improved more by the application of PCU than by split urea, especially under a high water supply from rainfall or irrigation. This is probably due to less N having been lost due to runoff and leaching when PCU was used. GYNUE was relatively stable across N treatments, but showed significant year-to-year variation, caused by variations in both the biomass N use efficiency (BNUE) (aboveground dry weight per N uptake) and harvest index (HI) as affected by rainfall conditions. The application of N increased root length from the surface to a below-45 cm depth, which may have contributed to the water exploitation under water stress. [ABSTRACT FROM AUTHOR]

The root is one of the most important plant organs due to its involvement in absorption of water and nutrients. The objective of this study was to determine if the application of micronutrients zinc (Zn), boron (B), and copper (Cu) could improve root growth of upland rice (Oryza sativa L.), common bean (Phaseolus vulgaris L.), corn (Zea mays L.), wheat (Triticum aestivum L.), and soybean (Glycine max L. Merr.) grown on an Oxisol. Zinc application did not have a significant effect on root dry weight of corn, wheat, and soybean. However, root dry weight of upland rice was significantly improved by the application of Zn. Zinc application had a significant negative effect on dry weight of common bean root. Boron significantly improved root dry weight of common bean and wheat. However, it had a significant negative effect on root dry weight of upland rice and corn. Root dry weight of soybean was not influenced by B application. Application of copper significantly increased root dry weight of upland rice and wheat. However, root dry weight of corn and soybean was significantly reduced with the application of copper. There was no significant influence of copper fertilization on the root dry weight of common bean. The root length and shoot-root ratio varied from crop species to species under different levels of Zn, B, and Cu. [ABSTRACT FROM AUTHOR]