Nutrient uptake and water use efficiency as affected by modified rice cultivation methods with reduced irrigation

A field experiment was conducted in 2005 to investigate the effects of modified rice cultivation methods on: water use efficiency, the uptake of nutrients (N, P and K) by plants, and their distribution within plants and their internal use efficiency. The treatments were modified methods of irrigation, transplanting, weeding, and nutrient management, comparing the System of Rice Intensification (SRI) with standard rice-growing methods including traditional flooding (TF). Results showed that the uptake of N, P, and K by rice plants during their growth stages was greater with SRI management compared to TF, except during the tillering stage. At maturity stage, SRI plants had taken up more nutrients in their different major organs (leaves, stems, and sheaths; panicle axis; and seeds), and they translocated greater amount of nutrients to the grain. Under SRI, the ratio of N, P, and K in seed grain to total plant N, P, and K was 4.97, 2.00, and 3.01% higher, respectively, than with TF. Moreover, under SRI management, internal use efficiency of the three macronutrients (N, P, and K) was increased by 21.89, 19.34, and 16.96%, respectively, compared to rice plants under TF management. These measurements calibrate the crop’s physiological response to differences in cultural practices, including the maintenance of aerobic versus anaerobic environment in the root zones. With SRI, irrigation water applications were reduced by 25.6% compared to TF. Also, total water use efficiency and irrigation water use efficiency was increased with SRI by 54.2 and 90.0%, respectively. Thus, SRI offered significantly greater water saving while at the same time producing more grain yield, in these trials 11.5% more compared to TF.     

Water productivity and nutrient status of rice soil in response to cultivation techniques and nitrogen fertilization

Three methods of rice cultivation were compared in a field experiment at New Delhi, India during 2012 for their water use and changes in nutrient availability of soil. The experiment was laid out in a split plot design with conventional transplanting (CT), system of rice intensification (SRI), and aerobic rice (AR) cultivation technologies. Five doses of nitrogen included 100 % (120 kg N ha^?1), 125, and 150 % recommended dose of N(RDN) through urea, 75 % of RDN through urea (90 kg N ha^?1) + 25 % of RDN (30 kg ha^?1) through farm yard manure (FYM), and 100 % of RDN through FYM. Results revealed that status of available N in soil under rice at 45 and 90 days after sowing (DAS) was significantly higher in CT and SRI compared to AR method. Application of the highest dose of nitrogen through urea resulted in the highest availability of N (188.9, 174.2, and 135.2 kg ha^?1 for 45 and 90 DAS and at harvest stage, respectively). The soil under AR recorded significantly low availability of phosphorus and iron. However, availability of K in soil was not affected significantly under adopted production techniques and nitrogen management. The recorded irrigation water productivity was maximum in AR cultivation (9.16 kg ha mm^?1) followed by SRI (7.02 kg ha mm^?1) with irrigation water saving of 54 and 36 %, respectively compared to CT.     

Water productivity,nutrients uptake and quality of aerobic rice as influenced by varieties and iron nutrition

Field experiments were carried out at the research farm of ICAR-Indian Agricultural Research Institute (ICAR-IARI), New Delhi, India, during Kharif (June–October) seasons of 2011 and 2012 to study the effect of rice varieties and iron fertilization on water productivity, nutrient uptake and quality of aerobic rice. Treatments comprised of two rice varieties (PRH-10 and PS-5) and eight sources and modes of iron fertilization—control (no iron), iron sulphate @ 50 kg/ha + one foliar spray of 2.0% iron sulphate, iron sulphate @ 50 kg/ha + one foliar spray of 0.5% iron chelate, iron sulphate @ 100 kg/ha, two foliar sprays of 2.0% iron sulphate, three foliar sprays of 2.0% iron sulphate, two foliar sprays of 0.5% iron chelate and three foliar sprays of 0.5% iron chelate. Study results indicated that variety PRH-10 had higher concentration and uptake of nitrogen, phosphorus, potassium and iron than PS-5 variety in grain, straw and grain + straw. Three foliar sprays of 2.0% iron sulphate or 0.5% iron chelate favoured higher NPK and iron concentration and uptake in grain and straw of aerobic rice. Grain quality in respect of hulling, milling and head rice recovery was, however, superior in PS-5 than PRH-10. But the protein content was significantly higher in PRH-10 than in PS-5. Application of three foliar sprays of 2% iron sulphate and three foliar sprays of 0.5% iron chelate recorded significantly higher hulling, milling and head rice recovery as compared to control and remained statistically similar with each other. Irrigation and total water productivity was substantially higher in PRH-10 over PS-5. Growing of rice with PRH-10 recorded ~7.7% higher total water productivity as compared to PS-5, across iron fertilizations. Three or two foliar sprays of 2.0% iron sulphate or 0.5% iron chelate favoured higher irrigation and total water productivity of aerobic rice over control (no iron).     

Water and energy productivity of rice as influenced by duration of cultivars,dates of transplanting and irrigation regime in north-western India

A field experiment was conducted to compare water productivity of short- and long-duration rice cultivars transplanted on different dates under variable irrigation regimes during 2012–2014. The experiment was laid out in split plot design keeping combinations of three dates of transplanting (15 June, 25 June and 5 July) and two cultivars (PR 115 and PR 118) in main plots and four irrigation regimes [irrigation at 1, 2 and 3 days after infiltration of ponded water (DIPW) and continuous ponding (CP)] in subplots. Crop transplanted on June 15 and 25 produced statistically similar but significantly higher grain yield than July 5 transplanted crop. Grain yield increased to the tube of 17.2 and 15.6% under early transplanting on June 15 and 25 compared to July 5, respectively. However, amount of irrigation water applied decreased by 23.6 and 12.9 cm for July 5 and June 25 transplanted crop compared to June 15 transplanted crop, respectively. Apparent crop water productivity (ACWP) and total crop water productivity (TCWP) were significantly higher in June 25 transplanted crop than in June 15 and July 5. Similarly, energy use efficiency and energy productivity were also the highest in June 25 transplanted crops followed by June 15 and the least in July 5. Significantly higher grain yield was observed in cultivar PR 118 as compared to PR 115 under June transplanting dates (15 and 25 June). However, reverse trend was observed in late transplanting on July 5. Significant reduction in grain yield of PR 118 was recorded with delay in transplanting from June 25 to July 5, but PR 115 performed statistically similarly under all the three dates of transplanting. Irrigation water applied was 9.4% higher in PR 118 as compared to PR 115. ACWP and TCWP were 7.9 and 9.2% higher in PR 115 than in PR 118, respectively. ACWP and TCWP of PR 115 increased with delay in transplanting from June 15 to July 5, but differences between June 25 and July 5 remained nonsignificant. However, in the case of PR 118, ACWP and TCWP remained statistically similar between June 15 and June 25 and thereafter decreased significantly with delay in transplanting to July 5. Rice grain yield did not show any significant effect on irrigation application frequency, i.e. irrigate continuously or applied water at 1, 2 and 3 DIPW. However, 5.9, 15.2 and 23.5% higher irrigation water applied was recorded in continuous ponding than in irrigation application at 1, 2, and 3 DIPW, respectively. Apparent water productivity and energy use efficiency were 5.9 and 7.0, 15.3 and 13.0, and 19.8 and 23.0% higher in irrigation scheduling at 1, 2 and 3 DIPW than in CP, respectively.     

Influence of rice varieties,nitrogen management and planting methods on methane emission and water productivity

A field experiment was conducted during rainy seasons of 2009 and 2010 at New Delhi, India to study the influence of varieties and integrated nitrogen management (INM) on methane (CH₄) emission and water productivity under flooded transplanted (FT) and aerobic rice (AR) cultivation. The treatments included two rice (‘PB 1’ and ‘PB 1121’) varieties and eight INM practices including N control, recommended dose of N through urea, different combinations of urea with farmyard manure (FYM), green manure (GM), biofertilizer (BF) and vermicompost (VC). The results showed 91.6–92.5 % lower cumulative CH₄ emission in AR compared to FT rice. In aerobic conditions, highest cumulative CH₄ emission (6.9–7.0 kg ha^?1) was recorded with the application of 100 % N by organic sources (FYM+GM+BF+VC). Global warming potential (GWP) was significantly lower in aerobic rice (105.0–107.5 kg CO₂ ha^?1) compared to FT rice (1242.5–1447.5 kg CO₂ ha^?1). Significantly higher amount of water was used in FT rice than aerobic rice by both the rice varieties, and a water saving between 59.5 and 63 % were recorded. Under aerobic conditions, both rice varieties had a water productivity of 8.50–14.69 kg ha^?1, whereas in FT rice, it was 3.81–6.00 kg ha^?1. In FT rice, a quantity of 1529.2–1725.2 mm water and in aerobic rice 929.2–1225.2 mm water was used to produce one kg rice. Thus, there was a saving of 28.4–39.6 % total water in both the rice varieties under AR cultivation.     

Yield, grain quality and water use efficiency of rice under non-flooded mulching cultivation

Plastic film or straw mulching cultivation under non-flooded condition has been considered as a new water-saving technique in rice production. This study aimed to investigate the yield performance in terms of quality and quantity and water use efficiency (WUE) under such practices. A field experiment across 3 years was conducted with two high-yielding rice cultivars, Zhendao 88 (a japonica cultivar) and Shanyou 63 (an indica hybrid cultivar) and four cultivation treatments imposed from transplanting to maturity: traditional flooding as control (TF), non-flooded plastic film mulching (PM), non-flooded wheat straw mulching (SM), and non-flooded no mulching (NM). Compared with those under the TF, root oxidation activity, photosynthetic rate, and activities of key enzymes in sucrose-to-starch conversion in grains during the grain filling period were significantly increased under the SM, whereas they were significantly reduced under the PM and NM treatments. Grain yield showed some reduction under all the non-flooded cultivations but differed largely among the treatments. The reduction in yield was 7.3–17.5% under the PM, 2.8–6.3% under the SM, and 39–49% under the NM. The difference in grain yield was not significant between TF and SM treatments. WUE for irrigation was increased by 314–367% under the PM, 307–321% under the SM, and 98–138% under the NM. Under the same treatment especially under non-flooded conditions, the indica hybrid cultivar showed a higher grain yield and higher WUE than the japonica cultivar. The SM significantly improved milling, appearance, and cooking qualities, whereas the PM or the NM decreased these qualities. We conclude that both PM and SM could significantly increase WUE, while the SM could also maintain a high grain yield and improve quality of rice. The SM would be a better practice than the PM in areas where water is scarce while temperature is favorable to rice growth, such as in Southeast China.     

Growth, yield and water productivity of zero till wheat as affected by rice straw mulch and irrigation schedule

Intensive cultivation of rice and wheat in north-west India has resulted in air pollution from rice straw burning, soil degradation and declining groundwater resources. The retention of rice residues as a surface mulch could be beneficial for moisture conservation and yield, and for hence water productivity, in addition to reducing air pollution and loss of soil organic matter. Two field experiments were conducted in Punjab, India, to study the effects of rice straw mulch and irrigation scheduling on wheat growth, yield, water use and water productivity during 2006-2008. Mulching increased soil water content and this led to significant improvement in crop growth and yield determining attributes where water was limiting, but this only resulted in significant grain yield increase in two instances. There was no effect of irrigation treatment in the first year because of well-distributed rains. In the second year, yield decreased with decrease and delay in the number of irrigations between crown root initiation and grain filling. With soil matric potential (SMP)-based irrigation scheduling, the irrigation amount was reduced by 75 mm each year with mulch in comparison with no mulch, while maintaining grain yield. Total crop water use (ET) was not significantly affected by mulch in either year, but was significantly affected by irrigation treatment in the second year. Mulch had a positive or neutral effect on grain water productivity with respect to ET (WP_ET) and irrigation (WP_I). Maximum WP_I occurred in the treatment which received the least irrigation, but this was also the lowest yielding treatment. The current irrigation scheduling guidelines based on cumulative pan evaporation (CPE) resulted in sub-optimal irrigation (loss of yield) in one of the two years, and higher irrigation input and lower WP_I of the mulched treatment in comparison with SMP-based irrigation scheduling. The results from this and other studies suggest that farmers in Punjab greatly over-irrigate wheat. Further field and modelling studies are needed to extrapolate the findings to a wider range of seasonal and site conditions, and to develop simple tools and guidelines to assist farmers to better schedule irrigation to wheat.     

Characterizing N uptake and use efficiency in rice as influenced by environments

To compare N uptake and use efficiency of rice among different environments and quantify the contributions of indigenous soil and applied N to N uptake and use efficiency, field experiments were conducted in five sites in five provinces of China in 2012 and 2013. Four cultivars were grown under three N treatments in each site. Average total N uptake was 10–12 g m^?2 in Huaiji, Binyang, and Haikou, 20 g m^?2 in Changsha, and 23 g m^?2 in Xingyi. Rice crops took up 54.6–61.7% of total plant N from soil in Huaiji, Binyang, and Haikou, 64.3% in Changsha, and 63.5% in Xingyi. Partial factor productivity of applied N and recovery efficiency of applied N in Changsha were higher than in Huaiji, Binyang, and Haikou, but were lower than in Xingyi. Physiological efficiency of soil N and fertilizer N were lower in Changsha than in Huaiji, Binyang, and Haikou, while the difference in them between Changsha and Xingyi were small or inconsistent. Average grain yields were 6.5–7.5 t ha^?1 (medium yield) in Huaiji, Binyang, and Haikou, 9.0 t ha^?1 (high yield) in Changsha, and 12.0 t ha^?1 (super high yield) in Xingyi. Our results suggest that both indigenous soil and applied N were key factors for improving rice yield from medium to high level, while a further improvement to super high yield indigenous soil N was more important than fertilizer N, and a simultaneous increasing grain yield and N use efficiency can be achieved using SPAD-based practice in rice production.     

Influence of crop establishment methods on yield,economics and water productivity of rice cultivars under upland and lowland production ecologies of Eastern Indo-Gangetic Plains

A field study on assessment of crop establishment methods on yield, economics and water productivity of rice cultivars under upland and lowland production ecologies was conducted during wet seasons (June–November) of 2012 and 2013 in Eastern Indo-Gangetic Plains of India. The experiment was laid-out in a split-plot design (SPD) and replicated four times. The main-plot treatments included three crop establishment methods, viz. dry direct-seeded rice (DSR), system of rice intensification (SRI) and puddled transplanted rice (PTR). In sub-plots, five rice cultivars of different groups like aromatic (Improved Pusa Basmati 1 and Pusa Sugandh 5), inbreds (PNR 381 and Pusa 834) and hybrid (Arize 6444) were taken for their evaluations. These two sets of treatments were laid-out simultaneously in two production ecologies, upland and lowland during both years. In general, lowland ecology was found favourable for rice growth and yield and resulted in 13.2% higher grain yield as compared to upland ecology. Rice grown with SRI method produced 19.4 and 7.0% higher grain yield in 2012 and 20.6 and 7.1% higher in 2013, over DSR and PTR. However, PTR yielded 13.1 and 14.5% higher grain over DSR during 2012 and 2013, respectively. On an average, Arize 6444 produced 26.4, 26.9, 28.9 and 54.7% higher grain yield as compared to PS 5, P 834, PNR 381 and IPB1, respectively. Further, the interaction of production ecologies × crop establishment methods revealed that, in upland ecology, SRI recorded significantly higher grain yield as compared to PTR and DSR, but in lowland, grain yield resulting from SRI was similar to the yield obtained with PTR and significantly higher than DSR. The latter two methods (PTR and DSR) yielded alike in lowland ecology in both study years. The production ecologies × crop establishment methods × cultivars interaction on grain yield showed that the growing of Arize 6444 cultivar using SRI method in upland ecology resulted in the higher grain yield (8.87 t/ha). But the cost of production was also highest in SRI followed by PTR and DSR across production ecologies and cultivars. Cultivation of hybrid (Arize 6444) involved higher cost of production than all other cultivars. Irrespective of crop establishment methods and cultivars, gross returns, net returns and B:C ratio were significantly higher in lowland compared to upland ecology. Owing to higher grain yield, SRI method fetched significantly higher gross returns and net returns over PTR and DSR. Average increase in net return with Arize 6444 was 68.8, 41.0, 37.7 and 33.1% over IPB 1, PNR 381, P 834 and PS 5, respectively. There was a saving of 30.7% water in SRI and 19.9% in DSR over PTR under upland ecology. Similarly in lowland ecology, water saving of 30.2% was observed in SRI and 21.2% in DSR over PTR. Due to higher yield and saving on water, SRI returned significantly higher total water productivity (TWP) (5.9 kg/ha-mm) as compared to DSR (3.5 kg/ha-mm) and PTR (3.6 kg/ha-mm) under upland ecology. In lowland ecology, also SRI (6.2 kg/ha-mm) resulted in higher TWP as compared to other two methods. However, DSR gave significantly higher TWP as compared to PTR. Among cultivars, hybrid Arize 6444 recorded the highest TWP in both upland and lowland production ecologies across crop establishment methods. Hence, growing of hybrid Arize 6444 with SRI method can enhance rice productivity and water-use efficiency in lowland and upland production ecologies of Eastern Indo-Gangetic Plains and in other similar regions.     

Crop establishment methods: foliar and basal nourishment of rice (<Emphasis Type="Italic">Oryza sativa</Emphasis>) cultivation affecting growth parameters,water saving,productivity and soil physical properties

A 3-year field experiment was carried out with tillage crop establishment (TCE) and rice nourishment in north-western India to evaluate the effect of five crop establishment methods and seven fertility treatments on crop production, water productivity, profitability, and soil physical quality. Maximum panicle length (30.9 cm) was noted with F₃ treatment and minimum (22.7 cm) with F₀ treatment. Zinc application methods and timing had significantly effect on paddy yield. Maximum yield (5.22 t ha^?1) was achieved in treatment F₃ and minimum yield (2.65 t ha^?1) was noted in F₀ treatment. Results also revealed that root dry weight, root volume, and root length were recorded with higher values in F₃ treatment and minimum in F₀ treatment. TCE methods were recorded with higher values in raised beds system than T₅ at all growth stages. Treatments T₁ and T₂ reduced the mean maximum soil temperature at transplanting zone depth by 3.6 and 2.7 °C compared to the T₃. Paddy yield in T₃ was always significantly less than in T₅. On average, treatment T₄ recorded about 13 % lower water use and 3.7 % higher water productivity compared to T₅. Treatment T₅ had higher bulk density. The cumulative infiltration for 498 min was about 2 times in treatment T₁, 5 times in T₃ and more than 8 times in T₄ of the values in T₅. Mean weight diameter of aggregates was higher in T₄ followed by the T₁ and lowest in T₅. The study reveals that TCE methods T₁ and T₄ with F₃ nourishment could be more viable options for rice crop in order to save input costs and enhance profitability.     

Alleviating soil sickness caused by aerobic monocropping: Responses of aerobic rice to nutrient supply

Yield decline is a major constraint in the adoption of monocropping of aerobic rice. The causes of the yield decline in the continuous aerobic rice system are still unknown. The objective of this study was to determine if nutrient application can mitigate the yield decline caused by continuous cropping of aerobic rice. Micro-plot experiment was conducted in 2005 dry season (DS) in a field where aerobic rice has been grown continuously for eight seasons from 2001 DS at the International Rice Research Institute (IRRI) farm. Pot experiments were done with the soil from the same field where the micro-plot experiment was conducted and aerobic rice has been grown continuously for 10 seasons. Apo, an upland rice variety, was grown under aerobic conditions with different nutrient inputs in field and pot experiments. The field micro-plot experiment showed that micronutrients had insignificant effect on plant growth under continuous aerobic rice cultivation but the combination of N, P, and K mitigated the yield decline of continuous aerobic rice. A series of pot experiments studying the individual effects of nutrients indicated that N application improved plant growth under continuous aerobic rice cropping, while P, K, and micronutrients had no effect. Increasing the rate of N application from 0.23 to 0.90 g per pot in the continuous aerobic rice soil increased the vegetative growth parameters, chlorophyll meter readings, and aboveground N uptake consistently. Our results suggested that N deficiency due to poor soil N availability or reduced plant N uptake might cause the yield decline of continuous cropping of aerobic rice.     

SRI as a methodology for raising crop and water productivity: productive adaptations in rice agronomy and irrigation water management

The System of Rice Intensification (SRI), developed in Madagascar almost 30 years ago, modifies certain practices for managing plants, soil, water, and nutrients with the effect of raising the productivity of the land, labor, and capital devoted to rice production. Certain production inputs are reduced—seeds, inorganic fertilizer, water, and fuel where water is pumped—with increased yield as a result. This paper introduces the subject of SRI, which is then addressed variously in the articles that follow. SRI is gaining interest and application in over 40 countries around the world. Its practices make soil conditions more aerobic and promote greater root growth, as well as larger, more diverse communities of beneficial soil biota. These below-ground changes support more productive phenotypes above-ground for practically all rice genotypes (cultivars) tested so far, with supportive evidence accumulating both from scientific institutions and field applications. SRI methodology remains controversial in some circles, however, because of the transformational change it introductions into traditional lowland rice production systems. This issue of PAWE brings together the results of formal research on SRI in a number of countries (Part I) and also reports on initiatives by government agencies, NGOs, universities, or the private sector, bringing knowledge of SRI to farmers in a wide range of agroecological circumstances (Part II). This introduction presents the basic principles that underlie SRI and discusses the nature of this innovation as well as considers some of the issues in contention. SRI continues to evolve and expand, being a work in progress. Its concepts and methods are being extended also to upland (rainfed) rice production, as well to other crops. Accordingly, SRI should not be regarded or evaluated in conventional terms as if it were a typical component technology. It is understood more appropriately in terms of a paradigm shift for rice production. In particular, it calls into question the long-standing belief that rice is best produced under continuously flooded conditions.     

Phyto-purification of livestock-derived organic waste by forage rice under subtropical climate

Soil and water pollution caused by organic waste is a concern for livestock-breeding areas. Nitrogen balance in a paddy-field water-purifying system in which cattle feces were applied was studied for 4 years to assess the suitability of the system for a subtropical area, Japan. Three successive harvestings using ratoon of forage rice following one rice transplanting were conducted with chemical fertilizer and high and low rates of cattle-feces application. Nitrogen load was 81.3–495.0 kg N ha^?1 year^?1, while nitrogen uptake was highly dependent on the yield of the first harvesting. Annual variation of forage rice yields was large, ranging from 15.5 to 26.8 Mg ha^?1 owing to fluctuation in the yield at second and later harvestings. On average, nitrogen was lost by leaching at a rate of 2.3–3.4 kg N ha^?1 year^?1. The nitrogen content in soil at a depth of 0–5 cm increased up to 12.2 kg N ha^?1 over the 4-year period compared with that before the field experiment. However, continuous application of cattle feces could slightly increase the nitrogen content in soil at a depth greater than 35 cm. Our results showed the ability of flooded forage rice to remove nitrogen at up to 320.1 kg ha^?1 year^?1 for a field to which cattle feces were applied. Further investigation is needed to produce a high and stable yield at second harvesting each year, to prevent the accumulation of soil nitrogen, and to assess gaseous nitrogen loss.     

Physicochemical characteristics of flours of faba bean as influenced by processing methods

Wet- and dry-processing with and without heating treatments were used to dehull faba beans for preparation of flours from the cotyledons. Flour qualities were assessed by levels of tannin and trypsin inhibitor and other measures of proximate composition. High roasting temperature and shorter process time that improved the recovered cotyledon yields were verified significant by path analysis methodologies. In turn, the higher cotyledon recoveries correlated with higher protein levels and inversely with the measured tannin levels. Ash reductions were correlated to the wet processing options in hull removal while reductions in the insoluble dietary fiber were notably influenced by level of heating temperatures applied. Trypsin inhibitor levels ranged from 42 to 56% of the original with reductions tied to applications of wet and/or heat processing in each case improved by increased durations and temperatures of treatments.     

Simulation of salt and water movement and estimation of water productivity of rice crop irrigated with saline water

The HYDRUS-ID model was experimentally tested for water balance and salt build up in soil under rice crop irrigated with different salinity water (ECiw) of 0.4, 2, 4, 6, 8 and 10 dS m⁻¹ in micro-lysimeters filled with sandy loam soil. Differences of means between measured (M) and HYDRUS-1D predicted (P) values of bottom flux (Q _o) and leachate EC as tested by paired t test were not found significant at P = 0.05 and a close agreement between RMSE values showed the applicability of the HYDRUS-1D to simulate percolation and salt concentration in the micro-lysimeters under rice crop. Potential ET values of rice as obtained from CROPWAT matched well with model predicted and measured one at all ECiw treatments. The model predicted root water uptake varied from 66.1 to 652.7 mm and the maximum daily salt concentration in the root zone was 0.46, 2.3, 4.5, 6.7, 8.4 and 10.2 me cm⁻³ in 0.4, 2, 4, 6, 8 and 10 dS m⁻¹ ECiw treatments, respectively. The grain production per unit evapotranspiration ( \textWP_{\textET\texta} {\text{WP}}_{{{\text{ET}}_{\text{a}} }} ) value of 2.56 in ECiw of 0.4 dS m⁻¹ treatment declined to 1.31 with ECiw of 2 dS m⁻¹. The \textWP_{\textET\texta} {\text{WP}}_{{{\text{ET}}_{\text{a}} }} reduced to one-fifth when percolation was included in the productivity determination. Similarly, the water productivity in respect of total dry matter production (TDM) was also reduced in different treatments. Therefore, the model predicted values of water balance can be effectively utilized to calculate the water productivity of rice crop.     

Yield response of long-term mixed grassland swards and nutrient cycling under different nutrient sources and management regimes

Abstract The response of a long‐term, mixed‐species hayfield in Maine, USA, to commercial fertilizers and liquid dairy manure was evaluated over a 6‐year period, including the effects on yield, nutrient concentration and cycling, forage species composition and soil nutrient levels. Nutrient treatments included an unamended control, N fertilizer, NPK fertilizer and liquid dairy manure (LDM). The application rates of plant‐available N, P, and K were constant across treatments. Application of nutrients in any form increased forage yield, generally by 2–4 t dry matter (DM) ha^?1 year^?1. Yield from NPK fertilizer was 0·05–0·25 higher than from LDM, due to differences in N availability. Yield responses to P and K were minimal and there appeared to be no difference between P and K in fertilizer and manure. The forage sward became increasingly dominated by grass species as the experiment progressed; application of P and K in fertilizer or LDM allowed Agropyron repens to increase at the expense of Poa pratensis. Forage nutrient removal accounted for all applied N and K, and nearly all applied P, throughout the study period, demonstrating the important role these forages can play in whole‐farm nutrient management.     

Growth and water relations of field-grown tall fescue as influenced by drought and endophyte

Field plots were established in autumn 1992 in which endophyte [ Neotyphodium coenophialum Glenn. Bacon, Price and Hanlin (formerly Acremonium coenophialum )]-infected (E⁺) and endophyte-free (E⁻) isolines of three tall fescue [ Festuca arundinacea Schreb.) genotypes were planted. Plants were subjected to three water-withholding periods in 1993 and one in 1994, or were kept well watered throughout the experiment. There were no consistent endophyte effects for leaf elongation, tiller density or dry weight per tiller. There were genotype X endophyte interactions ( P <001) for tiller density and shoot dry weight per area and genotype X water X endophyte interactions ( P <005) for cumulative leaf elongation in 1993. These interactions indicated the highly specific effect of host genotype-endophyte association on the expression of plant growth. Leaf rolling in the stressed treatments was more severe in E⁻ than in E⁺ plants in 1993, but there were no differences in 1994, and stomatal conductance tended to be lower in E⁻ than in E⁺ plants in 1993. Fractional water content of the lower 3 cm of the youngest fully developed leaf sheath was usually greater, and never less, in E⁺ than in E⁻ plants. The leaf rolling and stomatal conductance results suggest that E⁻ plants were more severely stressed in the summer after planting. Thus, the endophyte may induce greater water retention in the leaf sheath and therefore better protect the internal growing zone from lethal desiccation.     

Objective methods for testing potato flake quality as influenced by free starch and surfactants

A method was developed which uses changes in rates of retrogradation measured by a Brabender Amylograph to assess the complexing ability of surfactants for free starch in potato flakes during cooling. The rate of retrogradation was linearly related to surfactant concentration. A Blue Value Index method, adapted from use with cereal flours for determination of starch damage, was used to monitor the amount of free starch created by the required particle size reduction for Amylograph analysis. The change in Blue Value Index was also used to monitor the ability of surfactants to complex free starch and thereby influence potato flake quality. Distilled monoglyceride appeared to be more effective than sodiumor calcium stearoyl–2-lactylate. However, the combination of 0.3% distilled monoglyceride with 0.2% sodium stearoyl–2-lactylate was nearly as effective as 0.5% distilled monoglyceride in terms of free starch complexing ability. Instron back extrusion tests for mealiness of reconstituted flakes were found to be influenced by the level of free starch; therefore, back extrusion data should be accompanied by Blue Value Index data.     

Impact of water management on yield and water productivity with system of rice intensification (SRI) and conventional transplanting system in rice

The system of rice intensification (SRI) reportedly enhances yield with less water requirement. This claim was investigated to determine the effects of alternative cultivation methods and water regimes on crop growth and physiological performance. Treatment combinations compared SRI with the conventional transplanting system (CTS) using standard practices, evaluating both along a continuum from continuous flooding to water applications at 1, 3, 5, or 7 days after disappearance of ponded water (DAD), subjecting plants to differing degrees of water stress while reducing total water expenditure. SRI methods gave significant changes in plants’ phenotype in terms of root growth and tillering, with improved xylem exudation and photosynthetic rates during the grain-filling stage compared to CTS. This resulted in significant increases in panicle length, more grains and more filled grains panicle^?1, greater 1,000-grain weight, and higher grain yield under SRI management. Overall, averaged across the five water regimes evaluated, SRI practice produced 49 % higher grain yield with 14 % less water than under CTS; under SRI, water productivity increased by 73 %, from 3.3 to 5.7 kg ha-mm^?1. The highest CTS grain yield and water productivity were with the 1-DAD treatment (4.35 t ha^?1 and 3.73 kg ha-mm^?1); SRI grain yield and water productivity were the greatest at 3-DAD (6.35 t ha^?1 and 6.47 kg ha-mm^?1).     

Maize kernel growth and kernel water relations as affected by nitrogen supply

Improving maize (Zea mays L.) growing conditions near flowering by applying nitrogen (N) could affect both kernel number per unit area (KN) and potential kernel weight (KW). Potential kernel weight can be estimated with maximum kernel water content (MKWC), as final kernel weight and kernel water relations are strongly associated in maize. At the crop level, the product of KN per unit area and MKWC could provide an appropriate index of potential sink capacity. The main objective of this study was to determine if the decrease in potential sink capacity (i.e. the product of MKWC and KN), under N deficit and with a late planting date, is due to MKWC or KN reductions. Additionally, we evaluated sink growth rate per unit area (i.e. the product of KN and kernel growth rate) during grain fill period as related to potential sink capacity. Three N rates under optimal and late planting dates and two hybrids were evaluated in experiments carried out at Paraná, Argentina (31°50′S; 60°31′W) during 2002–2003 and 2003–2004 growing seasons (seasons 1 and 2, respectively). Except for the late planting date during season 1, there was a significant positive response on grain yield, KN, KW, and MKWC to N supply. Experiments explored a broad range of KN, from 1645 to 5066 kernel m⁻². MKWC and KN were positively correlated for DK682. Nitrogen increased the potential sink capacity and sink growth rate only as KN increases from a particular threshold in both hybrids. The sink growth rate was largely related to potential sink capacity, as MKWC was highly correlated with KGR across all treatments. Our analytical approach, considering potential sink capacity as a product of KN and MKWC, is integrative of sink demand both for individual kernel and crop levels. This work highlights the role of early establishment of potential sink capacity on yield determination under a wide range of N conditions.