Pot study on wheat growth in saline and waterlogged compacted soil: II. Root growth and leaf ionic relations

Abstract

Soil compaction affects plant growth by causing increased resistance to root penetration and a decreased uptake of water and ions. A pot experiment was conducted to study the effect of soil compaction in conjunction with the soil salinity and waterlogging on root growth and leaf ionic composition of two wheat genotypes (Aqaab and MH-97). Compaction was achieved at a 10% soil moisture content by dropping 5 kg weight, controlled by a tripod stand for 20 times from 0.6 m height on a wooden block placed inside the soil-filled pots. Soil bulk density of non-compact and compact treatments was measured as 1.21 and 1.65 Mg m −3, respectively. The desired salinity level (15 dS m −1) was developed by mixing required amount of NaCl in the soil before filling the pots. Waterlogging was developed by flooding the pots for 21 days both at tillering and booting stages. Compaction significantly reduced the root length density (RLD) of both the wheat genotypes while the combined effect of compaction×salinity was more drastic on root length density than compaction alone. Waterlogging however, did not decrease the root length density, rather it mitigated the effect of compaction. Compaction decreased the concentration of K + and K +:Na + ratio in leaves. Salinity also decreased the concentration of K + and K +:Na + ratio, but increased the concentrations of Na + and Cl − in the crop leaves. Salinity and compaction interacted to cause a greater reduction in K + concentration and the K +:Na + ratio, while there was lesser increase in the concentrations of Na + and Cl − compared with salinity alone. Waterlogging also decreased the concentration of K + and K +:Na + ratio in leaves. It intensified the effect of salinity but decreased the effect of compaction on leaf ionic composition. Therefore, the effect of compaction on root growth and ion uptake is more severe under salt-affected soil conditions than under normal soil conditions while occasional waterlogging of a compact soil for a few days makes the soil conditions favorable for root growth both under non-saline as well as saline soil conditions. Also, the performance of a genotype in stressed environment is related to maintenance of higher root length density, leaf K + concentration and K +:Na + ratio and lower leaf Na + and Cl − concentrations.