Phosphorus and rain harvested water economy through vesicular arbuscular mycorrhizae (VAM) in Okra-Pea sequence

Abstract

The present study was carried out during 2009-11 with the aim of economizing phosphorus and rain-harvested water through vesicular arbuscular mycorrhizal (VAM) fungi in okra-pea sequence. Use of VAM is highly desirable today from the perspective of meeting nutrient needs of crops efficiently and economically, rationalizing water use and maintaining soil health. Above work consisted of 14 treatments viz. 2 VAM levels (0 and 12 kg ha-1), 3 phosphorus levels (50, 75 and 100% of soil test based recommended dose) and 2 irrigation regimes (40 and 80% of available soil water holding capacity) and 2 controls (farmers nutrient practice and generalized recommended dose (NPK). Above treatments were laid out in a completely randomized block design (RBD) with 3 replications. The data on yield attributes, yields, nutrient uptake, net returns and B:C ratios in okra-pea sequence indicated that treatment VAM + 75 per cent soil test based recommended P dose at either of 2 irrigation regimes did not differ significantly than generalized recommended dose and VAM + 100 per cent soil test based recommended P dose . It suggests an economy of about 25 per cent in soil test based P dose through seed inoculation with mycorrhizal culture (VAM). The use of mycorrhizal biofertilizer (VAM) enhanced water use efficiency of okra and pea crop by about 5-17 and 12-35 per cent, respectively. Integrated application of VAM, P and irrigation did not alter available soil nutrient status significantly, however, available P status was enhanced by 15-20 per cent after harvest of each of the two crops i.e. okra and pea. Further, after completion of two years of okra-pea sequential cropping, integrated application of VAM, P and irrigation enhanced water holding capacity and mean weight diameter of soil particles by 5-6 and 4-9 per cent, respectively. Above practice evaluated in okra-pea sequence for two years, led to higher status of water soluble-P (10-32%), NaHCO3-Pi (8-13%), NaOH-Pi (5-13%) and low status of organic-P (NaHCO3-Po and NaOH-Po), each one of which contributed appreciably to available P supply to plants. Results of the current study suggest that the practice of VAM inoculation can go a long way in reducing the cost of production directly as well as otherwise. Moreover, its continuous use is going to enhance crop quality and overall soil fertility, which is the need of the hour.