Effects of Intercropping of Common Millet (Panicum miliaceum L.) - Cowpea (Vigna unguiculata L.) and Biological Fertilizer inoculation on Water and Nitrogen Use Efficiencies

IntroductionNowadays, increasing world population, destruction of natural resources followed by the confirmed need to increase food production are the basic challenges of the world. The appropriate solution for this challenge is sustainable agriculture based on consuming different kinds of biological and organic fertilizers, with the purpose of elimination and considerable decrease of agrochemicals. Phosphorus biological fertilizer consisted of two genus of bacteria, Bacillus spp. and Pseudomonas spp., helps plants to absorb phosphorus dissolved in soil by two mechanisms, excreting organic acids and phosphate enzyme.
Improving nitrogen use efficiency is a principle strategy to increase sustainability in agricultural systems. Some of management options which are effective on increasing nutrients efficiency in agro–systems are intercropping, rotation and green manure application. Utilizing fixed nitrogen of legumes by cereals is the advantage of intercropping legumes and cereals. Intercropping systems are practical and suitable samples for increasing water use efficiency in agriculture. Francis (9) believes that in case of water limitation, the best way to improve water use efficiency is intercropping.
The purpose of the present study was evaluating sole cropping system, intercropping common millet (Panicum miliaceum L.) and cowpea (Vigna unguiculata L.) and the role of biological fertilizer to achieve the most suitable combination of growing these two species crops and fertilizing recommendations with the purpose of suitable yield and resources use efficiency.
Materials and MethodsThis experiment was conducted at a farm in Najafabad-Isfahan, during growing season of year 2013-2014. The experimental treatments were arranged in split plots based on a randomized complete block design with three replications. Two levels of phosphorus biofertilizer a1 (seed inoculation with Bacillus spp. and Pseudomonas spp. rhizobacteria as Barvar 2 biofertilizer®) and a2 (control=no inoculation) were assigned to main plots. The sub-plots including b1 (sole cropping of millet), b2 (millet100% cowpea25%), b3 (millet100% cowpea50%), b4 (millet100% cowpea75%), b5 (millet100% cowpea100%) and b6 (sole cropping of cowpea). The distances between the rows in all treatments were 50 centimeters and the distance between two plants on each row of the sole millet was 8.6, for sole cowpea was 10.7 centimeters (with density of 200 and 160 thousand plants per hectare). In additive ratios the distances between the plants on all rows were 4.3 centimeters for millet as the fixed plant and 21.4, 10, 7, 7.1 and 5.4 cm for cowpea (with density of 4, 8, 12 and 16 plants per m2) which were on the parallel rows with millet.
Water use efficiency for grain yield was calculated from equation 1(8) and nitrogen efficiencies (including: recovery, Physiological and use) also were calculated by using the equation 2, 3 and 4 respectively.
Results and DiscussionThe results of this experiment showed that the effect of Barvar 2 biofertilizer® on WUE, NRE, NPE and NUE was significant (P≤0.05). In addition, the effect of cropping ratios on all measured traits was significant so that the most (0.704, 0.473 and 0.784 kg.m-3) water use efficiency, nitrogen recovery efficiency (77.7, 101.7 and 120.6%), nitrogen physiological efficiency (55.3, 37 and 66.8 kg.kg-1) and nitrogen use efficiency (43.2, 37.7 and 48.7 kg.kg-1) observed respectively for millet in ratio of millet 100% cowpea25%, for cowpea in sole cropping and for total two species also in ratio of millet100% cowpea25% was obtained.
ConclusionsThe results of this experiment showed that the management based on true understanding of ecological basis and principles of intercropping systems and application of biofertilizers could be an ecological approach for increasing productivity and best usage of resources (water and nitrogen) in order to achieve suitable production, decrease expenses and dependence to expensive foreign inputs, eliminate pollution and bioenvironmental pressures on sustainable agricultural systems.
Acknowledgements The authors are sincerely grateful to all the respectable anonymous persons that supported this research.