Sustainable Issues and Crop Diversification of the Rice-Wheat Cropping System for Higher Productivity and Resource Use Efficiency: A Review

The rice-wheat cropping system (RWCS) played a significant role in national food security. This system is having a huge potential to feed the increasing population of India. But with continuous adoption of the rice-wheat system, different issues and challenges have emerged and resulted in the decline or stagnated the productivity of this system. In these conditions’ diversification of the RWCS can be a viable option for higher productivity, profitability and efficient and sustainable use of available natural resources. This review mainly highlighted the major issues associated with the rice-wheat cropping system in India along with the alternate cropping system for crop diversification by substitution various crops viz. legume, maize, oilseed, fodder, vegetables and cash crop to tackle them. The comparison of various cropping system in term their crop productivity, economics analysis, water and nutrient productivity, and maintaining soil health.

Management of Fertigation in Horticultural Crops through Automation with Electrotensiometers: Effect on the Productivity of Water and Nutrients

Water and nutrient requirements of horticultural crops are influenced by different factors such as: Type of crop, stage of development and production system. Although greenhouse horticultural crops are more efficient in the use of water and fertilizers compared to other production systems, it is necessary increase efficiency for which individualized fertigation strategies must be designed for each greenhouse. The automation of fertigation based on the level of soil moisture allows optimization of management. The objective of this work was to determine the influence of the activation command of fertigation with electrotensiometers and the characteristics of the greenhouse on the productivity of the crop and the efficiency of use of water and nutrients in a sweet pepper crop. The trial was developed in two greenhouses. Four treatments were studied, combination of who two-factor: Soil matric potential (SMP) (SMP−10: Automatic activation of irrigation to −10 kPa and SMP−20: Automatic activation of irrigation to −20 kPa) and greenhouse characteristics (G1 and G2). The nutritive solution applied was the same in all treatments. The yield and volume of water and nutrients applied were determined, calculating the productivity of the water (WP), as well as productivity the nutrients. The fertigation activation threshold of −10 kPa presented the best results, increasing the yield and conserving WP and nutrient productivity with respect to −20 kPa in both greenhouses. The automation of irrigation with electrotensiometers allowed the application of different volume of fertigation demanded by the crop in each greenhouse, equalizing the WP and nutrient productivity without producing drainage. The pepper crop in the greenhouse G1 presented greater vegetative development, higher yield and demanded a greater volume of fertigation than G2 regardless of the activation threshold. This was due to the fact that the soil matric potential after irrigation in greenhouse G1 was closer to zero, being able to conclude that not only the soil matric potential threshold of irrigation activation has an influence on crop, but also the potential registered after irrigation. Soil matric potentials closer to zero are more productive.

Mangrove Productivity Estimation using Modelling Approach and Tree Parameters Assessment

This study used productivity models and above ground biomass to investigate productivity in different sites of MMFR. Ninety Rhizophora apiculata leaf samples were collected from different compartments (18, 31, 71, 74, 42 and 55) based on tree age and management. For biomass calculation, tree height and diameter were measured in plot of 10m x 10m in compartment 18, 31, 71, 74 and 67. The age of the trees were as follows: compartment 18 and 31 with 15-year-old, compartment 71 and 74 with 25-year-old and compartment 67 with 30-year-old mangrove trees. Compartment 42 and 55 are classified as virgin jungle reserve (VJR). Compartment 67 was not taken as a sample site due to technical reason and compartments in VJR were not considered for biomass estimation. Sixteen variables; stable isotopes (δ13C, δ15N), macronutrients (C, N, P), cations (Ca, Mg, Na, K) and trace elements (Cd, Cu, Fe, Mn, Pb, Zn) were analyzed. Productivity models and calculated biomass for investigated compartments showed similar trends. In 15-year age group; compartment 18 showed higher productivity than in 31. For the 25-year age group; compartment 74 had higher productivity than 71. No prominent increase was observed in biomass between 15-year old and 30-year old trees. Furthermore, with moderate N and δ15N loading input, compartments showed more productivity. The results conclude that MMFR is a sustainably managed mangrove forest and its productivity could be monitored using nutrient productivity models.

Antarctic subglacial hydrology: current knowledge and future challenges

Flood-carved landforms across the deglaciated terrain of Victoria Land, East Antarctica, provide convincing geomorphological evidence for the existence of subglacial drainage networks beneath the Antarctic ice sheet, and motivate research into the inaccessible environment beneath the contemporary ice sheet. Through this research, our understanding of Antarctic subglacial hydrology is steadily building, and this paper presents an overview of the current state of knowledge. The conceptualization of subglacial hydrological behaviour was developed at temperate and Arctic glaciers, and is thus less mature in the Antarctic. Geophysical and remote sensing observations have demonstrated that many subglacial lakes form part of a highly dynamic network of subglacial drainage beneath the Antarctic ice sheet. Recent research into subglacial water flows, other than those directly concerned with lakes, has discovered potentially significant impacts on ice stream dynamics, ice sheet mass balance, and supplies of water to the ocean potentially affecting circulation and nutrient productivity. Despite considerable advances in understanding there remain a number of grand challenges that must be overcome in order to improve our knowledge of these subglacial hydrological processes.

Water and nutrient productivity in melon crop by fertigation under subsurface drip irrigation and mulching in contrasting soils

Cropping intensification and technical, economic and environmental issues require efficient application of production factors to maintain the soil productive capacity and produce good quality fruits and vegetables. The production factors, water and NPK nutrients, are the most frequent limiting factors to higher melon yields. The objective of the present study was to identify the influence of subsurface drip irrigation and mulching in a protected environment on the water and NPK nutrients productivity in melon cropped in two soil types: sandy loam and clay. The melon crop cultivated under environmental conditions with underground drip irrigation at 0.20m depth, with mulching on sandy loam soil increased water and N, P2O5 and K use efficiency.

Effects of Photon Flux Density on Nutrient Productivity in Eucalyptus grandis Seedlings

In plants in which growth is limited by the availability of phosphorus, phosphorus productivity is defined as the plants' relative growth rate divided by their internal phosphorus concentration. An experiment was conducted to assess whether phosphorus productivity was dependent on photon flux density, or whether photon flux density only set an upper maximum relative growth rate below which phosphorus productivity remained constant with changing photon flux density. Eucalyptus grandis seedlings were grown in growth units in which plants were suspended in air while continuously being sprayed with nutrient solution (aeroponic system). Plants were grown at five different relative phosphorus addition rates, and under natural lighting over the period from late summer to mid-winter when daily photon flux density decreased from about 30 to 10 mol quanta m-2 d-1. Relative growth rate was then plotted as a function of internal phosphorus concentration for a series of harvests. For the three highest relative phosphorus addition rates, there was a negative relationship between relative growth rate and internal phosphorus concentration. For the two lowest phosphorus addition rates, the internal phosphorus concentration increased throughout the experiment, while relative growth rate remained almost constant. This meant that phosphorus productivity changed throughout the experiment. When phosphorus productivity was expressed as a function of daily photon flux density, a linear relationship between phosphorus productivity and photon flux density was obtained. That relationship had a positive intercept on the axis of photon flux density which was interpreted as the plants' light compensation point. This finding has important implications for applications of the concept of nutrient productivity to the modelling of ecosystems in which growth is limited by nutrient availability.

Developmental potentialities of leaf primordia of Osmunda cinnamomea. II. Further studies on the influence of determined leaf primordia on undetermined leaf primordia

In the fern Osmunda cinnamomea, leaf primordia may be excised and grown in sterile culture before or after their irreversible determination as leaves. It has been demonstrated that P3 primordia (third most recently formed primordia) are not irreversibly determined as leaves at the time of excision for they exhibit a tendency to develop as whole shoots (approximately 67.0% of the time) whether grown singly, or as pairs grown in physiological contact. Results from the present investigation support the hypothesis that a morphogenetic factor(s) is found in older primorida which is transmitted to younger primordia to influence the latter to develop as leaves rather than shoots, for P3's grown in physiological contact (as pairs) with P10, P12, or P13 primordia are expressed as leaves at a level approximately twofold or greater than P3's grown singly (controls). Results from the present investigation do not support the hypothesis that increased bulk of tissue, and therefore increased capacity for nutrient productivity by older and larger primordia, is responsible for imposition of leafness on undetermined P3 primordia, for P14 primordia grown in physiological contact with P3 primordia (as pairs) are observed to increase the percentage of P3's expressing leafness at a level only slightly greater than P3's grown singly, and slightly less than when P3's are grown in physiological contact with other P3's as pairs. The slight enhancement in leafness exhibited by undetermined P3's grown as pairs with other P3's, or with P14's has been shown to be non-significant at the 5% level (P < 0.05) by the standard t test and Kramer's (1956) modification of Duncan's (1955) new multiple range test.