Effect of different densities of parthenium weed (Parthenium hysterophorus L.) on the performance of direct-seeded rice under aerobic conditions

Parthenium weed (Parthenium hysterophorus L.) is an emerging weed species in direct-seeded aerobic systems of rice production. This two-year field study was conducted to evaluate the effect of five different densities (0, 5, 10, 15 and 20 plants m^?2) of parthenium weed on rice yield and yield-related attributes. Parthenium weed produced ca. 38 to 178% higher biomass at its densities of 10 to 20 plants m^?2 as compared to the lowest density of 5 plants m^?2. The paddy yield and yield-related attributes were negatively affected with an increase in the parthenium weed density. In both years, the highest reductions in number of rice panicles (14 to 17%), panicle length (10 to 11%), number of grains per panicle (11 to 18%), 1000-grain weight (8 to 21%) and paddy yield (30 to 35%) were recorded at the highest parthenium weed density (20 plants m^?2) tested. However, the lower densities of 5 to 15 parthenium weed plants m^?2 also caused 11 to 24% and 12 to 26% losses in paddy yield during the years 2016 and 2017, respectively. Therefore, this weed species should be controlled below the density of 5 plants m^?2 to avoid the substantial yield losses (over 15%) in direct-seeded rice.     

Effect of continuous and intermittent irrigation methods on rice (cv. Koohrang) yield

This study was carried out to evaluate the impact of permanent and intermittent irrigation on the yield of rice (cv. Koohrang) in Lordegan rice-growing areas in Chaharmahal and Bakhtiari Province (Iran). The experiment was set up in a randomized complete block design with four treatments and four replications during 2003 and 2004. Irrigation treatments were: I1, continuous irrigation with a 5-cm water head every day; I2, alternative irrigation with a 5-cm water head every 2 days; I3, alternative irrigation with a 5-cm water head every 4 days; and I4, alternative irrigation with a 5 cm water head every 6 days. Results showed that the paddy yield was highest under treatment I2 (5655.6 kg ha^?1) and lowest under treatment I4 (3421.3 kg ha^?1). The highest rate of water use was obtained in I1 with 17 687.5 m³ ha^?1 and the lowest in I4 with 9325 m³ ha^?1. Paddy yield, plant height, panicle length and 1000-seed weight did not show a significant difference at the 5% level among I1, I2 and I3, but differed significantly to I4. Thus irrigation treatment I3 is appropriate for paddy irrigation in the Lordegan region with 10 645 m³ ha^?1 water use and 5483.7 kg ha^?1 paddy yield.     

Effect of nitrogen and wheat residue on cotton (Gossypium hirsutum L.) yield and weed control

Wheat (Triticum aestivum L.) residues and nitrogen (N) management are the major problems in the southern part of Iran where irrigated wheat–cotton (Gossypium hirsutum L.)–wheat rotation is a common practice. A 2-year (2009–2011) field experiment was conducted as a split plot design with four replications at a cotton field (Darab), Fars Province, Iran, to determine the influence of different rates of wheat residue (0%, 25%, 50%, and 75%) incorporation and N rates (150, 200, 300, and 400 kg ha^?1) on weed suppression, yield, and yield components of cotton. Results showed that a higher residue incorporation and a lower N rate improved weed suppression in both years. For treatments receiving 150 kg N ha^?1 and 75% of wheat residues (2250 kg ha^?1), weed biomass and density were significantly lower compared to treatments receiving 400 kg N ha^?1. The highest cotton lint yield (about 2400–2700 kg ha^?1) was obtained by 300 kg N ha^?1 in the absence of residue application, in both years. Incorporation of 25% of wheat residue (750 kg ha^?1) and application of 300 kg N ha^?1 are recommended to guarantee an optimum level of cotton lint yield and weed suppression in a wheat–cotton–wheat rotation in this region.     

Conservation tillage and mulching effects on the adaptive capacity of direct-seeded upland rice (Oryza sativa L.) to alleviate weed and moisture stresses in the North Eastern Himalayan Region of India

A field experiment was conducted to study the effects of tillage and mulch on weed growth, soil moisture storage, productivity and profitability of upland rice during 2012–2013 at Lembucherra, India. Tillage treatments included CT-RI: conventional tillage with 100% residue incorporation and NT-RR: no-till with 100% residue retention. Mulches included rice straw (SM), Gliricidia (GM), brown manuring (BM) and none (NM). CT-RI registered the highest total weed density (89–168 weeds m^?2) and biomass (9.6–183 g dry weight m^?2) than those for the NT-RR (75–161 weed m^?2 and 8–155 g dry weight m^?2). In addition, NT-RR stored (122–172 mm) more soil moisture (0–40 cm soil depth) in comparison with that for the CT-RI treatment (110–161 mm) during crop growing season. Tillage treatments did not have the significant effect on yields. NT-RR reduced the cost of cultivation by 31.5% compared with that for the CT-RI. Thus, the net returns under NT-RR were more than those for the CT-RI. The BM recorded the lowest weed biomass and density as compared to that under other mulches. Therefore, cultivation of upland rice using NT along with BM mulching enhanced productivity and profitability of rice cultivation in India.     

Evaluation of alternate menthol mint (Mentha arvensis L.) based intensive cropping systems for Indo-Gangetic plains of north India

The objective of the study was to determine the profitability and employment-generation potential of different cropping systems involving menthol mint (Mentha arvensis L.) as a component of sequential/intercropping in comparison with the most common paddy–wheat–green gram cropping system. Field experiments were conducted at Lucknow, India (26° 5′ N, 80° 5′ E and 120 m above mean sea level) for three years from July 2004 to June 2007. Menthol mint yielded the maximum fresh shoot biomass and essential oil (21.0 t and 151 kg ha^?1, respectively) grown after sweet basil (Ocimum basillicum)–potato followed by paddy–potato–menthol mint (18.9 t and 136 kg ha^?1, respectively) and maize–mustard–menthol mint (17.7 t and 131 kg ha^?1, respectively). Net returns of all the menthol-mint-based cropping systems were 82.6–354% higher than traditional paddy–wheat–green gram cropping system. Maize–garlic–menthol mint + okra was found to be most profitable (77,200 Rs ha^?1) followed by pigeon pea + sweet basil–menthol mint + okra (76,120 Rs ha^?1). Employment-generation efficiency was much higher in cropping systems involving menthol mint and vegetable crops, the highest (2.21 man days ha^?1 day^?1) being in a maize–cauliflower–onion–menthol mint + okra cropping system.     

Optimizing water,nitrogen and crop density in canola cultivation using response surface methodology and central composite design

Abstract

Optimisation of water and nitrogen use is an effective management tool to conserve resources and reduce environmental pollutions. Response surface methodology (RSM) is defined as a collection of mathematical and statistical methods that are used to develop, to improve or to optimize a product or process. In order to determine optimum levels of water, nitrogen and planting density of canola (Brassica napus L.), a 2-year experiment (2010–2011) was carried out by central composite design as RSM at the research station of Ferdowsi University of Mashhad. The treatments were designed based on low and high levels of irrigation (1500 and 4000 m³ ha^?1), nitrogen (0 and 400 kg N ha^?1) and density (50 and 150 plant m^?2) as independent variables. Furthermore, seed yield, nitrogen losses, nitrogen use efficiency (NUE) and water use efficiency (WUE) were measured as response variables in a full quadratic polynomial model. Optimum levels of irrigation, nitrogen and planting density were suggested to achieve the target range of dependent variables based on three scenarios: economic, environmental and eco-environmental. The results showed that increasing irrigation and fertilizer led to an increase in seed yield and nitrogen losses, whereas increasing canola density resulted in an increase in seed yield but a decrease in nitrogen losses. The optimum levels of water, fertilizer and density based on environmental scenario were 1802 m³ ha^?1, 11 kg N ha^?1 and 122 plant m^?2, respectively. To achieve optimum conditions under the economic scenario, it is necessary to use 3411 m³ water ha^?1, 178 kg N ha^?1 and 119 plant m^?2. Amounts of 2347 m³ water ha^?1, 92 kg N ha^?1 and 114 plant m^?2 were found to be the optimum conditions for the eco-environmental scenario. In general, it seems that resource use based on the eco-environmental scenario may be the most favorable cropping strategy for canola production.     

Response surface optimization of cultivation conditions for yield of tomato (Lycopersicon esculentum Mill.) in greenhouses

There is a great potential for greenhouse tomato fruit yield improvement in China for the low yield per hectare. We evaluated the effects of multi-factors (plant density, nitrogen (N) and K₂O fertilizer) on fruit yield of tomato (Lycopersicon esculentum Mill. cv. Jinfan 4) by response surface methodology with a 5-level-3-factor central composite design. A multivariate quadratic regression model of fruit yield was established. Results showed that N fertilizer was the most significant for fruit yield, followed by K₂O fertilizer and plant density. Fruit yield showed a parabolic trend with increasing fertilizer levels or plant density. There was a significant interaction effect between plant density and fertilizer levels. Optimal conditions were obtained: 4.83 × 10⁴ plants ha^?1 for density, 262 kg ha^?1 for N and 513 kg ha^?1 for K₂O. Under these conditions, the predicted fruit yield was 119,381 kg ha^?1, while the actual fruit yield from verification test was 121,005 kg ha^?1.     

Diversification of rice (Oryza sativa L.)-based cropping systems for higher productivity,resource-use efficiency and economic returns in south Gujarat,India

The continuous growing of rice has led to a deterioration in soil quality, resulting in a serious threat to agricultural sustainability in the high rainfall zone of south Gujarat, India. Therefore, crop diversification with a wider choice in the production of crop varieties is being promoted to restore the soil quality. A field experiment was conducted in Navsari, India during 2003–2007 on a Vertisol to evaluate the productivity, sustainability, resource-use efficiency and economics of 10 rice-based cropping systems. The results showed that system productivity for rice–fenugreek (Trigonella foenum-graecum)–okra (Abelmoschus esculentus) was highest (25.73 t ha^?1), followed by rice–onion (Allium cepa)–cowpea (Vigna sinensis L.) (24.15 t ha^?1); and the lowest system productivity was observed with the rice–wheat (Triticum aestivum)–fallow system (7.85 t ha^?1). The sustainable yield index (0.97), production efficiency (102.94 kg ha^?1 day^?1) and field water use efficiency (15.98 kg ha^?1 mm^?1) were maximum with the rice–fenugreek–okra system. Similarly, net return (96,286 Rs ha^?1), net return per rupee invested (2.83 Rs), monetary production efficiency (385.14 Rs ha^?1 day^?1) and water use efficiency (59.80 Rs ha^?1 mm^?1) were maximum with the rice–fenugreek–okra cropping sequence. There were significant effects of various cropping sequences on available nitrogen, phosphorus, potassium and organic carbon content in the soil. Overall, the rice–fenugreek–okra system was found to be the most productive, sustainable, resource-use efficient and remunerative cropping system, followed by the rice–onion–cowpea system.     

Diversified nitrogen rates influence nitrogen agronomic efficiency and seed yield response index of sesame (Sesamum Indicum,L.) cultivars

ABSTRACT

Due to elevating costs of N fertilizer and growing apprehensions about nitrate, experiments evaluating nitrogen agronomic efficiency (NAE) is becoming increasingly important in crop production. NAE and seed yield potentiality of three cultivars of sesame (Shandwel–1, Giza–32 and Sohag–1) were evaluated under four N applications (0, 72, 108, and 144 kg N ha^?1) in a field experiment. Results showed that Sohag–1 recorded the highest values of yield and yields traits surpassing the other two cultivars. Sesame plants received 144 or 108 kg N ha^?1 produced the highest seed yield. In plots fertilized by 108 or 144 kg N ha^?1, Sohag–1 was the potent cultivar for recording higher seed yield. N addition more or less than 108 kg N ha^?1 caused suppression in NAE. Sohag–1 was the most effective and responsive cultivar in N use being exceeded the averages of each seed yield at zero N rate and seed yield response index (SYRI).     

Real-time nitrogen management in aerobic rice by adopting leaf color chart (LCC) as influenced by silicon

Leaf color chart (LCC) guides fertilizer nitrogen (N) application to rice as per requirement of the crop on the basis of a critical leaf color. Two field experiments were conducted to evaluate the effect of silicon (Si) and LCC based N management in aerobic rice. Following LCC-based N management, from 60 to 90 kg N ha^?1 and 75 to 100 kg N ha^?1 with 10–40% and 25–30% less fertilizer N was used without any reduction in yield as compared to the package of practices of 100 (50 kg N ha^?1 as basal + two split of 25 kg N ha^?1) kg N ha^?1 respectively, during both the seasons. The highest grain yield was noticed with 90 kg N ha^?1 (30 kg N ha^?1 as basal + LCC-3) and 100 kg N ha^?1 (50 kg N ha^?1 as basal + two split of 25 kg N ha^?1) along with the application of calcium silicate (CaSiO₃) at 2 t ha^?1 as sources of Si and on par with 60 kg N ha^?1 (no basal + LCC-3) and 75 kg N ha^?1 (30 kg N ha^?1 as basal + LCC-3), respectively, during the season in 2008 and 2009. Higher fertilizer N use efficiency was recorded with Si and need-based N management using LCC-3 rather than recommended dose of fertilizer N.     

Water use efficiency of rice (Oryza sativa L.) under intermittent ponding and different intensity of puddling

Abstract

To increase the water use efficiency (WUE) of rice, two sets of experiments were carried out from 1997 – 1999. Experiment one: Irrigation period of rice was divided into three stages: early (S₁, 10 – 35 days after transplanting, [DAT]); middle (S₂, 36 – 60 DAT) and late (S₃, 61 – 85 DAT). Intermittent ponding (IP) was imposed at single, two stages or the entire growing period. Continuous ponding (CP) in all three stages was taken as control. Though the highest grain yield (6.71 mg ha^?1) was obtained under control, this regime was responsible for the lowest WUE. In contrast, IP in all stages was responsible for maximum WUE with minimum yield level. Imposition of IP in S₁ resulted in higher (0.529 kg m^?3) WUE along with insignificant reduction in yield over control. Experiment two: Three puddling practices were: (i) High intensity puddling (HIP); (ii) Moderate intensity puddling (MIP); and (iii) Low intensity puddling (LIP). On average, HIP resulted in the lowest value (6.5 mm d^?1) of percolation rate. Both grain yield (6.93 mg ha^?1) and WUE (0.597 kg m^?3) attained highest value under HIP. A decrease in puddling intensity under MIP and LIP lowered the yield by 2.97 and 17.75% respectively. In the case of WUE, the reduction was 16.27 and 54.66%.     

Combining effect of allelopathic Sorghum bicolor L. (Moench) cultivars with planting densities on companion weeds

Field experiments were conducted to compare the effects of allelopathic sorghum cultivars ‘Enkath’ and ‘Rabeh’ at three planting densities (6.6, 13.3 and 26.6 plant m^?2) on weed growth and sorghum yields in 2009 and 2010. Sorghum planting densities suppressed average weed population by 26–42% and average weed biomass by 46–57% compared with weedy check in 2009. A similar trend in the reduction in weed population and weed biomass was observed in 2010. Planting densities at 6.6, 13.3 and 26.6 plant m^?2 significantly suppressed average weed population by 26, 31 and 42% and average weed biomass by 88, 91 and 96% compared with weedy check, respectively, during 2009. A similar trend in effect was also recorded during 2010. Enkath cultivar reduced average weed density and dry biomass by 25 and 44% during 2009 and by 23 and 30% in 2010 compared with Rabeh cultivar. Root exudates of Enkath inhibited more weed growth than Rabeh. Increased planting density significantly increased average grain yield of sorghum. The highest grain yield of sorghum (12.68 t ha^?1) was recorded in plots in which the planting density was 26.6 plant m^?2.     

Effect of split application of zinc on yield of rice (Oryza sativa L.) in an inceptisol

Abstract

Rice is mostly transplanted under puddled low land soil conditions in India, where Zinc (Zn) deficiency is a common problem. The objective of this study was to find out the efficacy of split application of Zn on growth and yield of rice in an inceptisol. The split application of Zn as ZnSO₄ · 7H₂O performed better than its single basal application, while the split application of Zn-EDTA did not show any significant difference on yield and yield components of rice over its single basal application. Zn-EDTA was found to be better for growth and yield of rice among the two sources of Zn. The soil application of Zn at 1.0 kg ha^?1 as Zn-EDTA (T₇) recorded highest grain yield of 5.42 t ha^?1, filled grain percentage of 90.2%, 1000-grain weight of 25.41 g and number of panicles m^?2 of 452. The Zn content of grain and straw were found to be maximum in the treatment T₇ i.e. 38.19 and 18.27 mg kg^?1, respectively. Linear regression studies indicated that grain yield of rice is significantly influenced by Zn content of grain, Zn content of straw and DTPA extractable Zn content of soil at the level of 95.96, 96.74 and 95.57%, respectively.     

Interactive effect of brassinolide and lime on growth and yield of maize (Zea mays L.) on acid soils of South-East Nigeria

ABSTRACT

Our aim was to determine the combined effect of brassinolide (BR) and lime on the growth and yield of maize on acid soils of South East Nigeria using two BR levels (0 and 250 mL), two maize varieties [Ikom White (IKW) and Oba-98] and two lime levels (0 kg ha^?1 and 500 kg ha^?1). The IKW was better (P ≤ 0.05) in growth morphology than Oba-98; however, Oba-98 was more (p ≤ 0.05) efficient in intercepting radiation (420.16 μmol m^?2s^?1) than IKW (325.08 μmol m^?2s^?1). The 500 kg ha^?1 lime plus BR improved (P ≤ 0.05) nitrogen (N) uptake, dry matter yield, harvest index, shoot to root ratio, and grain yield, especially in Oba-98. Thus, the interactive action of BR and lime could increase the soil pH to an extent for enhanced yield of hybrid maize.     

Agronomic evaluation of rice cultivation systems for water and grain productivity

Field experiments were conducted during summer (March–July) and kharif (June–September), 2008 at the wetland farm, Tamil Nadu Agricultural University, Coimbatore, India, to study the performance of different rice cultivation methods on productivity and water usage using the hybrid CORH-3 as a test crop. Treatments consisted of different rice cultivation methods, namely, transplanted rice (conventional), direct sown rice (wet seeded), alternate wetting and drying method (AWD), system of rice intensification (SRI) and aerobic rice cultivation. Results revealed that maximum number of tillers m^?2, higher shoot and root length at maturity were recorded under SRI followed by transplanted rice, while aerobic rice produced lower growth parameters in both the seasons. Chlorophyll content at flowering was higher under SRI in two seasons studied (42.74 and 39.48 SPAD value, respectively) and transplanted rice compared to aerobic rice and AWD. In both summer and kharif seasons, SRI produced higher grain yield (6014 and 6682 kg ha^?1), followed by transplanted rice (5732 and 6262 kg ha^?1), while the lowest grain yield (3582 and 3933 kg ha^?1) was recorded under aerobic rice cultivation. Under SRI, 5 and 6.7% increase in grain yield and 12.6 and 14.8% water saving were noticed compared to transplanted rice, respectively, during summer and kharif seasons. In respect to water productivity, the SRI method of rice cultivation registered the highest water productivity (0.43and 0.47 kg m^?3), followed by AWD and aerobic rice cultivation. The conventional rice cultivation and direct sown rice produced lower grain yield per unit quantity of water used.     

Phosphorous and beneficial microorganism influence yield and yield components of wheat under full and limited irrigated conditions

Field experiment was conducted to investigate the impact of phosphorus (P) and beneficial microorganism (BM) on the yield and yield components wheat (Triticum aestivum L., cv. Siren-2010). The experiment was conducted under full (five irrigations) and limited (two) irrigation conditions at the Research Farm of The University of Agriculture Peshawar during winter 2012–13. The experiment under both full and limited irrigated conditions was laid out in randomized complete block design using three replications. The results showed that irrigated plots produced more spikes m^?2 (254), grains spike^?1 (55.5), heavier thousand grains weight (39.4 g), and higher grain yield (3612 kg ha^?1 than limited irrigated condition. Application of P at the highest rate (90 kg P ha^?1) produced more spikes m^?2 (260) and grains spike^?1 (52.4), and increased maximum thousand grain weight (39.1 g) and grain yield (3617 kg ha^?1). Application of BM at the highest rate (30 L ha^?1) resulted in maximum number of spikes m^?2 (257) and grains spike^?1(51.7), highest thousand grains weight (39.1 g) and grain yield (3765 kg ha^?1). The results confirmed that under full irrigated condition the increase in both P and BM levels (90 kg P ha^?1 and 30 L ha^?1, respectively) and under limited irrigated condition the intermediate levels of both P and BM (60 kg P ha^?1 and 20 L ha^?1, respectively) could increase wheat productivity under semi-arid conditions.     

Effect of nutrient management and straw mulching on crop yield,uptake and soil fertility in rapeseed (Brassica campestris)–greengram (Vigna radiata)–rice (Oryza sativa) cropping system under Gangetic plains of India

An experiment was conducted at Bidhan Chandra Krishi Viswavidyalaya, West Bengal, India during 2001–2003 to study the effect of levels of fertility and straw mulch on a rapeseed (Brassica campestris var yellow sarson)–greengram (Vigna radiata)–rice (Oryza sativa) cropping system under a rainfed upland ecosystem. The experiment was laid out in a split-plot design having 14 treatment combinations of organic and inorganic nutrients along with straw mulch in three replicates. The results revealed that conjunctive use of organic and inorganic nutrients as well as paddy straw mulch resulted higher yield in both rapeseed and greengram, and the residual effects of different levels of fertilization and mulching also gave rise to higher grain yield in the succeeding rice crop. The uptake of nutrients, by the cropping system as a whole, to the tune of 204.29 and 183.00 kg ha^?1 of N, 72.84 and 74.07 kg ha^?1 of P and 179.95 and 175.41 kg ha^?1 of K took place, with the treatment receiving 10 t ha^?1 of farmyard manure (FYM) applied (to rapeseed) along with 50% recommended dose (RD) of NPK to all the crops in the sequence in two consecutive years, respectively. The same treatment resulted in a higher percentage of porosity vis-à-vis lower bulk density. Soil physico-chemical properties were superior in mulch-treated plots compared with no mulch treatment. Application of organic and inorganic nutrients along with proper moisture conservation practices can enhance the yields maintaining a good soil health.     

Optimum application level of winter cover crop biomass as green manure under considering methane emission and rice productivity in paddy soil

The combined seeding and cropping of non-leguminous and leguminous cover crops during the cold fallow season is recommended as an important agronomic practice to improve total biomass productivity and soil fertility in mono-rice (Oryza sativa L.) cultivation system. However, application of plant residues as green manure can increase methane (CH₄) emission during rice cultivation and affect rice quality and productivity, but its effects are not well examined. In this field study, the mixture of barley (Hordeum vulgare R.) and hairy vetch (Vicia villosa R., hereafter, vetch) seeds with 75 % recommended dose (RD 140 kg ha^?1) and 25 % RD (90 kg ha^?1), respectively, were seeded after rice harvesting in late November, 2010, and harvested before rice transplanting in early June 2011. Total aboveground biomass was 36 Mg ha^?1 (fresh weight basis with 68 % moisture content), which was composed with 12 Mg ha^?1 of barley and 24 Mg ha^?1 of vetch. In order to determine the optimum recycling ratio of biomass application that can minimize CH₄ emission without affecting rice productivity, different recycling ratios of 0, 25, 50, 75, and 100 % of the total harvested biomass were incorporated as green manure 1 week before rice transplanting in a typical temperate paddy soil. The same rates of chemical fertilizers (N–P₂O₅–K₂O?=?90–45–58 kg ha^?1) were applied in all treatments. Daily mean CH₄ emission rates and total CH₄ fluxes were significantly (p?<?0.05) increased with increasing application rates of cover crop biomass. Rice productivity also significantly (p?<?0.05) increased with biomass application, but the highest grain yield (53 % increase over the control) was observed for 25 % recycling. However, grain quality significantly (p?<?0.05) decreased with increasing cover crop application rates above 25 % recycling ratio, mainly due to extended vegetative growth periods of rice plants. Total CH₄ flux per unit grain yield, an indicator used to simultaneously compare CH₄ emission impact with rice production, was not statistically different between 25 % biomass recycling ratio and the control but significantly increased with increasing application rates. Conclusively, the biomass recycling ratio at 25 % of combined barley and vetch cover crops as green manure might be suitable to sustain rice productivity without increasing CH₄ emission impact in mono-rice cultivation system.     

Soil-Test-Based Optimum Fertilizer Doses for Attaining Yield Targets of Rice under Midland Alfisols of Eastern India

Soil-test crop-response experiments on rice were conducted in the Bastar Plateau Agroclimatic Zone of Chhattisgarh during 2009–2011 to assess yield, soil, plant, and fertilizer nitrogen (N), phosphorus (P), and potassium (K) nutrient relationships and calibrate optimum fertilizer doses for attaining yield targets. Soil fertility status was poor to medium for N (194–283 kg ha^?1) and P (7.53–19.66 kg ha^?1), and medium to good for K (226–320 kg ha^?1). Based on nutrient requirements (NR, kg q^?1) and contributions from soil (CS, %), fertilizer (CF, %), and farmyard manure (CFYM, %), optimum fertilizer doses were derived. The fertilizer doses were validated for attaining yield targets of 5000 and 6000 kg ha^?1 in farmer’s fields. Rice yield within 10% deviation was attained, which indicated that soil-test-based fertilizer dose was superior. This approach could be adopted for regions with similar soil and agroclimatic conditions in other parts of the world to increase rice yields.     

Optimum Fertilizer Phosphorus Requirement for Maximum Productivity under Rice–Rice and Rice–Sunflower Systems in Semi-Arid Alfisols

A study was conducted at Hyderabad during 2009–11 to determine phosphorus (P) dose for rice–rice and rice–sunflower. Available P increased when 100% recommended P dose (RDP) was applied. P applied to rice gave at par yield under 100 or 75% RDP. In rice–rice, grain yield of 5668 and 5775 kg ha^?1 in kharif (5654 and 5760 kg ha^?1 in rabi) were attained with P@75 and 100% RDP. Kharif P residual effect in rabi affected rice yield. P@100/75% RDP in kharif and rabi gave grain of 5916/5973 and straw 6230/6673 kg ha^?1. P applied to sunflower revealed that yield was similar with 100 or 75% RDP. Sunflower yield was at par with P@100 or 75% RDP. 25% RDP in rice and sunflower may be reduced to attain similar yield of 100% RDP. In rice–rice, grain yield attained by 100% RDP in both seasons was 11.42t ha^?1 yr^?1, while 75% RDP gave yield of 11.45t ha^?1yr^?1.